JP5486700B2 - Image display device, image region detection method, and computer program - Google Patents

Description

  The present invention relates to an image display device, an image region detection method, and a computer program that can detect an image region of a specific condition included in an input image and display the image region with display characteristics suitable for the image region.

  In recent years, color image display apparatuses using a liquid crystal panel or a PDP (Plasma Display Panel) have been widely used. For example, an image display device for medical use is used for displaying an image by X-ray photography, displaying an image taken by an endoscope, and the like.

  The image display device performs correction processing (so-called gamma correction processing) for converting pixel values of an input image from a PC (Personal Computer) or the like into pixel values suitable for display characteristics of the image display device. In an image display device for medical use, since a suitable display characteristic is different between a monochrome (hereinafter simply referred to as monochrome) image obtained by X-ray photography and a color image obtained by photography using an endoscope or the like, an optimal correction process is performed on the display image. It is desirable to do so.

  However, in recent years, an OS (Operating System) installed in a PC has a multi-window system, and can display a plurality of windows on an image display device. For this reason, in an image display device for medical use, a monochrome image obtained by X-ray photography and a color image such as an endoscope may be displayed simultaneously on one screen. There is a problem that it is difficult to properly perform the correction process.

  In Patent Document 1, it is determined whether or not a color picture is included in a screen and whether or not a monochrome picture is included. When it is determined that a color picture is included, a monochrome picture is included without including a color picture. A display device has been proposed that changes the display image quality by changing the luminance, color temperature, and gamma characteristics when it is determined that both pictures are not included. This display device can change the display image quality only by processing on the display device side according to the screen, for example, a color picture display image quality suitable for displaying a screen including an image obtained by color-taking a natural object such as a flower. And a monochrome picture display quality suitable for displaying an X-ray image and a text display quality suitable for displaying a text screen created by an editor can be automatically switched.

  In Patent Document 2, a gradation correction lookup table for each area to be corrected is provided so that gradations in an area obtained by dividing a display screen by a predetermined number become substantially uniform gradations over the entire screen. There has been proposed an image display device configured to detect a display position by taking in a signal and perform gradation correction based on a gradation correction lookup table of an area corresponding to the detected position information.

  However, the display device of Patent Document 1 is configured to change the display image quality of the entire screen according to the determination result. When displaying a color picture and a monochrome picture at the same time, the display image quality for each display area of each picture is improved. There is a problem that it cannot be changed.

  In the image display device described in Patent Document 2, in order to solve the problem that the intensity of the backlight light or the transmittance of the panel differs depending on the display position and the position dependency of the display characteristics of the image occurs, In this configuration, a plurality of gradation correction lookup tables are used. For this reason, the image display device described in Patent Document 2 cannot perform appropriate correction according to the type of image, such as a color picture and a monochrome picture. The image display device disclosed in Patent Document 2 is configured to perform correction using a different gradation correction lookup table for each predetermined region, and detect a display region such as a color picture and a monochrome picture in a displayed image. Cannot be corrected.

  In Patent Document 3, when reading an image, each page determines whether it is color or black and white from the color pixel ratio, and stores it as page information, and refers to the page information at the time of transmission. There has been proposed an image transmission apparatus that performs compression-coding with a coding method and transmits the data, and in the case of black and white, performs compression-coding with a black-and-white coding method. Further, Patent Document 3 describes that a read original image is divided into a color area and a monochrome area in each page, and the image information of the color area and the image information of the monochrome area are stored in different forms. Has been.

  As in the image transmission apparatus described in Patent Document 3, it is conceivable to separate a color area and a monochrome area in a display image even in an image display apparatus. Thus, the image display apparatus can perform correction processing for each divided area, and can display an image with characteristics suitable for each area.

JP 2006-126528 A Japanese Patent Laid-Open No. 11-98438 JP-A-6-253155

  The image transmission device described in Patent Document 3 has a configuration in which color or monochrome determination is performed for each pixel of image data, and a color area included as a rectangular area in an image is classified. However, the image displayed by the image display device is not only a monochrome image such as X-ray photography or a color image such as an endoscope, but also an image in which color characters are entered in a monochrome image or monochrome characters are entered in a color image. In many cases, monochrome and color are mixed in a complicated manner as in the case of a printed image. When a plurality of images in which monochrome and color are mixed are displayed in a multi-window or the like, if the color area and the monochrome area are determined on a pixel-by-pixel basis as in the image transmission apparatus described in Patent Document 3, color There is a problem that erroneous determination of a region occurs due to the presence of monochrome characters in the region or color characters in the monochrome region. Similarly, even when the region is determined for each line of the display image or the entire image, there is a possibility that erroneous determination of the region may occur due to the presence of monochrome characters in the color region or color characters in the monochrome region. is there. Further, in the multi-window system, it is possible to display a part of a plurality of windows in an overlapping manner, and an erroneous determination of the area may occur when a part of a color area and a monochrome area are displayed overlapping each other. There is.

  The present invention has been made in view of such circumstances, and an object of the present invention is to accurately detect an image area (for example, a color image area or a monochrome image area) of a specific condition existing in a display image. Another object of the present invention is to provide an image display device, an image area detection method, and a computer program capable of realizing display with display characteristics suitable for an image area.

The image display device according to the present invention is an image display device that displays an input image composed of a plurality of lines each including a predetermined number of pixels, and whether each pixel in the input image is an effective pixel that satisfies a specific condition. Effective pixel determining means for determining whether or not, effective line area detecting means for detecting an effective line area composed of a plurality of effective pixels from each line in the input image, and orthogonal to the line from the input image an effective image area detecting means for detecting an effective image area composed of a plurality of valid line regions adjacent in the direction, the effective image region detected each pixel in the input image by the effective image region detection unit when included, the effective image Ri Citea to be displayed in display characteristics associated with regions, the effective line area detecting means, the head of the line or the effective line of the input image The effective line area included in the line following the line not including the area is set as the start line area, and for the lines after the line including the start line area, the coordinate difference in the line direction with respect to the end point of the start line area is within a predetermined value. The area is detected as an effective line area .

  Also, the image display device according to the present invention is characterized in that the effective line area detecting means detects an area on a line where a predetermined number or more of effective pixels are continuous as an effective line area.

In addition, the image display device according to the present invention includes the effective line region even if the region on the line where the effective pixels are continuous includes a region where pixels other than the predetermined number or less of the effective pixels are continuous. It is characterized by being detected as.

  Further, the image display device according to the present invention is characterized in that the effective image area detecting means detects an area including a predetermined number or more of effective line areas as the effective image area.

  In the image display device according to the present invention, the effective pixel determination means determines an effective pixel depending on whether each pixel is a monochrome pixel or a color pixel. And

The image region detection method according to the present invention is an image region detection method for detecting an image region composed of pixels satisfying a specific condition from an image composed of a plurality of lines each including a predetermined number of pixels. It is determined whether each pixel in the image is an effective pixel satisfying a specific condition, and from each line in the image, an effective line area composed of a plurality of effective pixels is detected, and from the image, When an effective image area composed of a plurality of effective line areas adjacent to each other in a direction orthogonal to the line is detected, and the effective line area is detected , the next of the first line of the image or the line not including the effective line area The effective line area included in the line is defined as the start line area, and the lines following the line including the start line area are aligned in the line direction with respect to the end points of the start line area. Difference a region within a predetermined value, and detecting as an effective line area.

A computer program according to the present invention is a computer program for causing a computer to detect an image area composed of pixels satisfying a specific condition from an image composed of a plurality of lines each including a predetermined number of pixels. An effective pixel determining step for determining whether each pixel in the image is an effective pixel satisfying a specific condition; and an effective line region configured by a plurality of effective pixels from each line in the image. An effective line area detecting step for detecting the effective image area, and an effective image area detecting step for detecting an effective image area composed of a plurality of effective line areas adjacent to each other in a direction orthogonal to the line from the image, the effective line area detecting step, including the head of the line or the effective line region of the image An effective line area included in a line next to a non-line is a start line area, and for a line after the line including the start line area, an area in which a coordinate difference in a line direction with respect to an end point of the start line area is within a predetermined value, It is detected as an effective line area .

  In the present invention, it is determined whether an input image from a PC or the like is an effective pixel satisfying a specific condition (color or monochrome), and a plurality of effective pixels are formed from each line constituting the input image. An effective line area constituted by pixels is detected, and an effective image area constituted by a plurality of effective line areas adjacent in a direction orthogonal to the line is detected. Thereby, an effective image area composed of effective pixels satisfying the specific condition can be detected from the input image. Further, the display device displays the detected effective image area and another image area (invalid image area) with different display characteristics. Thereby, for example, a monochrome image area and a color image area can be displayed with optimum display characteristics.

  Further, in the present invention, even when a region where valid pixels are continuous includes a region where a predetermined number or less of invalid pixels are continuous, this region is detected as an effective line region. For example, when characters or the like due to invalid pixels are written in the effective pixel area, the continuation of the effective pixels is interrupted. However, if this is shorter than a predetermined number, it is possible to prevent the effective line area from being determined to be invalid.

  In the present invention, when an effective line area is detected from each line constituting the input image, an area where a predetermined number or more of effective pixels continue is detected as an effective line area. If there are consecutive effective pixels less than the predetermined number, for example, there is a high possibility that the characters are valid pixels written in the invalid pixel area, and therefore it is possible to prevent these from being erroneously detected as the effective line area.

  In the present invention, when detecting an effective line area from the input image, if an effective line area is detected in the first line of the input image or the line next to the line determined to be invalid, the effective line area is started. Line area. In an image display such as a multi-window system, one image region is often a rectangular region, and the start points or end points of a plurality of effective line regions included in the same effective image region often coincide substantially. Therefore, for the lines after the line including the start line area, the effective line area is detected as an effective line area if the number of valid pixels continues for a predetermined number or more and the amount of deviation from the start point and end point of the start line area is within a predetermined value. To do. Thereby, the image area displayed as a substantially rectangular area can be detected with high accuracy.

  In the present invention, when detecting an effective image area, an area including a predetermined number or more of adjacent effective line areas is detected as an effective image area. Even if the effective line areas are adjacent to each other, if the number of the effective line areas is less than the predetermined number, there is a possibility that the effective line area is detected due to an erroneous determination. Therefore, it is possible to prevent erroneous detection of effective image areas by determining whether or not the number of effective line areas is equal to or greater than a predetermined number and detecting the effective image areas.

In the present invention, whether each pixel in the input image is a monochrome pixel or a color pixel is determined as to whether it is an effective pixel. For example, when each pixel has an RGB value, a monochrome pixel that satisfies R = G = B (or R≈G≈B) as a specific condition is determined as a valid pixel, and other color pixels are invalidated It can be determined as a pixel.
This makes it possible to distinguish between a monochrome image area composed of monochrome pixels and a color image area composed of color pixels, and display each image area with optimal display characteristics.

In addition, after performing the above process for all lines of the input image, the image area that could not be detected by the above process may be redetected as an effective image area by performing redetection of the effective image area. For example, if there are invalid pixels (pixels other than valid pixels) in the effective image area, such as when there are monochrome characters in the color image area or color characters in the monochrome image area, the influence of invalid pixels Therefore, even when the above processing is performed, there is a possibility that an erroneous detection of the effective image area may occur. In the multi-window system, it is possible to display a part of a plurality of windows in a superimposed manner, but this is also effective because a part of the color area and the monochrome area may be displayed in an overlapping manner. There is a risk of erroneous detection of the image area.
The re-detection of the effective image area is performed for one or a plurality of lines that exist between the two effective image areas detected by the above processing and do not include the effective line area. A line erroneously determined to be invalid due to an invalid pixel in the effective image area is likely to exist between two correctly determined effective image areas. By making it a target of re-detection, an effective image area can be detected efficiently and reliably.
The re-detection of the effective image area is performed according to the position of the end point (start point or end point) of the two effective image areas. In an image display such as a multi-window system, one image region is often a rectangular region, and the start points or end points of a plurality of effective line regions included in the same effective image region often coincide substantially. Therefore, an effective line that has not been detected due to the influence of invalid pixels in the effective image area is obtained by performing re-detection processing from the line between the two effective image areas in accordance with the start point or end point of the two effective image areas. The area can be detected again efficiently and reliably.

  Further, when the start point or the end point of the two effective image areas are at the same position in the line direction, the re-detection process may be performed on the line between the two effective image areas. For example, in an image display such as a multi-window system, one image area is often a rectangular area, and several lines in one effective image area are erroneously determined to be lines that do not include an effective line area. When the image area is divided into two, there is a high possibility that the start points or end points of the two effective image areas substantially coincide. Therefore, the erroneously determined line can be relieved by setting a line between two effective image areas whose start points or end points substantially coincide with each other as a target of re-detection.

  In addition, when the number of lines between two effective image areas is equal to or less than a predetermined number, re-detection processing may be performed for these lines. If there are more than a certain number of lines between two effective image areas, it is likely that the two effective image areas are independent of each other, so the line between the two effective image areas is re-detected. Not subject to

  When the two effective image areas have different sizes, an image area obtained by adding a part of the line between the two effective image areas to one effective image area having a small size in the line direction is set as a new effective image area. By detecting, re-detection processing of the effective image area may be performed. If a part of the line is added to the other effective image area having a large size in the line direction, an invalid pixel may be added, which can be prevented.

  In the case of the present invention, it is determined whether or not each pixel is an effective pixel satisfying a specific condition, an effective line region composed of a plurality of effective pixels is detected, and a plurality of effective pixels adjacent to each other in a direction orthogonal to the line are detected. By performing the process of detecting the effective image area constituted by the line areas for all the lines of the input image, the effective image area constituted by the effective pixels satisfying the specific condition can be detected from the input image.

It is a block diagram which shows the structure of the image display apparatus which concerns on this invention. It is a schematic diagram for demonstrating a color LUT and a monochrome LUT. It is a schematic diagram which shows one structural example of an input image. It is a functional block diagram which shows the structure of the image process part which concerns on a monochrome image area | region detection process. It is a schematic diagram for demonstrating the process of a boundary expansion | extension means. It is a schematic diagram for demonstrating the process of a monochrome line area | region detection means. It is a schematic diagram which shows one structural example of image area information. It is a schematic diagram for demonstrating the process of a start / end point check means. It is a schematic diagram for demonstrating the process of a color check means. It is a schematic diagram for demonstrating the process of an image area adjustment means. It is a schematic diagram for demonstrating the process of an image area adjustment means. It is a flowchart which shows the procedure of the monochrome image area detection process which an image display apparatus performs. It is a flowchart which shows the procedure of the monochrome image area detection process which an image display apparatus performs. It is a flowchart which shows the procedure of the image display process which an image display apparatus performs.

  Hereinafter, the present invention will be specifically described with reference to the drawings showing embodiments thereof. FIG. 1 is a block diagram showing a configuration of an image display apparatus according to the present invention. In the figure, reference numeral 1 denotes a color image display device including a liquid crystal panel 19 as a display device, and displays an image input from the PC 9. The image display device 1 can be used, for example, for medical purposes, and can display a monochrome image by X-ray photography, a color image by photography such as an endoscope, and other images (text, graph, table, etc.). .

  The image display apparatus 1 includes a control unit 11, a ROM (Read Only Memory) 12, a RAM (Random Access Memory) 13, a backlight driving unit 14, a liquid crystal driving unit 15, an operation unit 16, an image input unit 17, a backlight 18, The liquid crystal panel 19 and the image processing unit 40 are provided. Specifically, the control unit 11 can be configured by an arithmetic processing device such as a CPU (Central Processing Unit) or an MPU (Micro Processing Unit), and exchanges information with each unit in the image display device 1 to exchange these information. By controlling the operation of each unit, various processes for displaying an image on the liquid crystal panel 19 are executed.

  The ROM 12 is configured by a nonvolatile memory element such as an EEPROM (Electrically Erasable Programmable ROM) or a flash memory, for example, and a control program 21 necessary for the operation of the control unit 11 and other various data (not shown). Is stored in advance.

  The RAM 13 is configured by a data rewritable memory element such as SRAM (Static RAM) or DRAM (Dynamic RAM), for example, and can store temporary data such as image area information 31 (details will be described later). it can. For example, the control unit 11 can perform various processes by reading out and executing the control program 21 stored in the ROM 12, and can temporarily store data generated in the calculation process of the process in the RAM 13.

  The operation unit 16 includes various function keys for the user to scan the image display device 1. For example, for setting the display characteristics of the image display device 1 such as a key for changing the brightness (brightness) of the image display of the liquid crystal panel 19 or a key for changing the color balance of the image display. A setting key is provided on the operation unit 16. The operation unit 16 accepts user operations on these function keys and notifies the control unit 11, and the control unit 11 can control the operation of each unit in response to the notification from the operation unit 16.

  The image input unit 17 has a connection terminal connected to an external device such as the PC 9 via a signal cable, and acquires an image signal input from the PC 9. The image signal is composed of a plurality of colors such as RGB or CMY, and is input for each color. The image signal is subjected to various image processing such as brightness adjustment or color balance adjustment by the image processing unit 40 and then applied to the liquid crystal driving unit 15, and the liquid crystal driving unit 15 performs liquid crystal display according to the applied image signal. By driving the panel 19, the image display device 1 can perform image display based on the image signal from the PC 9. The image signal input from the PC 9 to the image input unit 17 may be either an analog signal or a digital signal.

  Although not shown, the image processing unit 40 includes an arithmetic processing unit for performing arithmetic processing related to image processing and a non-volatile storage unit. The non-volatile storage unit includes a color LUT (lookup). Data necessary for image processing such as a table 41 and a monochrome LUT 42 are stored in advance. The image processing unit 40 performs various image processing on the image signal given from the image input unit 17 under the control of the control unit 11, and gives the image signal after the image processing to the liquid crystal driving unit 15. In particular, in the present embodiment, the image processing unit 40 performs image processing (so-called gamma correction) for correcting the gradation value of the image signal from the image input unit 17 in accordance with the color LUT 41 and the monochrome LUT 42.

  The liquid crystal panel 19 has a structure in which a pair of glass substrates are opposed to each other and a liquid crystal layer, which is a liquid crystal substance, is formed in the gap. One glass substrate is provided with a plurality of pixel electrodes and TFTs (Thin Film Transistors) each having a drain connected to the pixel electrode, and the other glass substrate is provided with a common electrode. The gate and source of each TFT are connected to a gate driver and a source driver (not shown) of the liquid crystal drive unit 15, and drive signals are input from the liquid crystal drive unit 15, respectively.

  The liquid crystal drive unit 15 outputs a drive signal for driving the liquid crystal panel 19 in accordance with the supplied image signal. Specifically, the gate driver of the liquid crystal driving unit 15 applies a voltage selectively to the gates of a large number of TFTs of the liquid crystal panel 19 in accordance with a given image signal, and similarly, the source of the liquid crystal driving unit 15 The driver applies a voltage to the source of the TFT with a voltage value corresponding to the input video signal. As a result, the liquid crystal panel 19 controls the on / off of the TFT of each pixel by the voltage applied from the gate driver of the liquid crystal driving unit 15, and outputs the output voltage (to the liquid crystal panel 19) input from the source driver of the liquid crystal driving unit 15. Is applied to the TFT of each pixel, the light transmittance determined by the electro-optical characteristics of the liquid crystal substance is controlled, and the transmission of light from the backlight 18 is adjusted, so that a desired image can be obtained. Gradation can be displayed. Each pixel of the liquid crystal panel 19 is further composed of sub-pixels for a plurality of colors such as RGB, and color display is possible by arranging a color film in the light transmission direction.

  The backlight 18 is disposed on the back side of the liquid crystal panel 19 in the image display device 1 and is driven by an output voltage supplied from the backlight driving unit 14. The backlight drive unit 14 adjusts the output voltage to the backlight 18 under the control of the control unit 11. Accordingly, for example, the brightness of the backlight 18 can be adjusted by causing the backlight drive unit 14 to adjust the output voltage in accordance with the brightness setting set by the user operating the operation unit 16. For example, when a pulsed voltage is applied from the backlight driving unit 14 to the backlight 18, the adjustment of the output voltage by the backlight driving unit 14 may be performed by changing the amplitude of the pulse (so-called amplitude modulation) The pulse width may be changed (so-called pulse width modulation).

  As described above, the image display device 1 can perform image display according to the image signal by driving the backlight 18 and the liquid crystal panel 19 in accordance with the image signal input from the PC 9. At this time, the control unit 11 of the image display device 1 corrects the gradation value of the image signal (input image) input from the PC 9 to the image input unit 17 to a gradation value suitable for the display characteristics of the liquid crystal panel 19. The processing given to the liquid crystal drive unit 15 is performed by the image processing unit 40, and the color LUT 41 and the monochrome LUT 42 stored in advance in the storage unit of the image processing unit 40 are used for the correction processing. The color LUT 41 and the monochrome LUT 42 are tables in which the gradation value of the input image is associated with the gradation value of the output image to be supplied to the liquid crystal driving unit 15. The optimum value is stored so as to obtain an ideal display characteristic.

  FIG. 2 is a schematic diagram for explaining the color LUT 41 and the monochrome LUT 42, and shows the display characteristics of the image display apparatus 1 as a graph. In the graph shown in FIG. 2, the horizontal axis represents the input gradation (gradation value of the input image from the PC 9), and the vertical axis represents the display gradation (gradation value of the image actually displayed on the liquid crystal panel 19). The display characteristic of the image display apparatus 1 is illustrated. The display characteristic indicated by the solid line in the graph is a characteristic when a color image is displayed, and is a characteristic when the gamma value is 2.2. The display characteristics indicated by the alternate long and short dash line in the graph are characteristics when a monochrome image in DICOM (Digital Imaging and Communications in Medicine) format used for medical images such as an X-ray image is displayed.

  The image display device 1 corrects the gradation value of the input image from the PC 9 using the color LUT 41 and the monochrome LUT 42 so that the display characteristics shown in FIG. The color LUT 41 and the monochrome LUT 42 store the output gradation corresponding to the input gradation of the input image, and the output gradation is given by an inverse function of the display characteristics shown in FIG. That is, the color LUT 41 stores a value corresponding to the inverse function of the display characteristic indicated by the solid line in FIG. 2, and the monochrome LUT 42 stores a value corresponding to the inverse function of the display characteristic indicated by the dashed line in FIG. ing.

  Therefore, the image display apparatus 1 performs gradation value correction processing by converting the gradation value of the input image given from the PC 9 into the output gradation value stored in the color LUT 41 or the monochrome LUT 42, thereby correcting the gradation value. By displaying the image on the liquid crystal panel 19 at a later output gradation, the image can be displayed with display characteristics substantially linear with respect to the input gradation from the PC 9.

  However, as described above, the display characteristics of the image display apparatus 1 are different between when a color image is displayed and when a monochrome image is displayed. The OS (Operating System) installed in the PC 9 includes a multi-window system, and an input image from the PC 9 to the image display device 1 is an image in which a plurality of windows are arranged or overlapped. The image may be either a color image or a monochrome image. For this reason, the image display apparatus 1 according to the present embodiment detects a monochrome image area included in the input image, performs correction processing using the monochrome LUT 42 on the detected monochrome image area, and also performs a monochrome image. Correction processing using the color LUT 41 is performed using an image area other than the area as a color image area.

  Next, a monochrome image region detection process from an input image performed by the image display device 1 will be described. First, as a premise, the configuration of an input image input from the PC 9 to the image display device 1 will be described. FIG. 3 is a schematic diagram illustrating a configuration example of an input image. In FIG. 3, only a part of the head of the input image (for three lines) is illustrated, pixels constituting the input image are indicated by squares, and color pixels are indicated by hatching. Each pixel is composed of a plurality of subpixels such as RGB, but the removal of these subpixels is omitted in FIG. One input image given as an image signal from the PC 9 has a predetermined number of pixels, and is configured by arranging a predetermined number of these pixels vertically and horizontally. An arrangement of one horizontal line of pixels in the input image is called a line (in FIG. 3, one line is composed of 41 pixels), and the input image is constituted by arranging a predetermined number of lines in the vertical direction. A vertical line of images in an input image is called a column. The number of pixels in the line direction (horizontal direction) in the input image is called width, and the number of pixels in the vertical direction is called length. An area where monochrome pixels are continuous in one line is called a monochrome line area (see a portion surrounded by a broken line in FIG. 3), and an area where a plurality of monochrome line areas are adjacent in the vertical direction (direction perpendicular to the line). This is referred to as a monochrome image region (see the portion surrounded by the one-dot chain line in FIG. 3).

  Processing for detecting a monochrome image region from the input image is performed by the image processing unit 40 of the image display device 1. FIG. 4 is a functional block diagram showing the configuration of the image processing unit 40 related to the monochrome image region detection process. The image processing unit 40 of the image display device 1 first performs a process of extending the boundary of the input image by a boundary extending means 51 (denoted simply as boundary expansion in FIG. The detection means 52 performs processing for detecting a monochrome line area from the input image, and the monochrome image area detection means 56 performs processing for detecting a monochrome image area. Further, the image processing unit 40 performs re-detection of the monochrome image region by performing image region adjustment processing by the image region adjustment unit 57 on the detection result by the monochrome image region detection unit 56. The processing results of each process are stored as image area information 31 in the RAM 13 of the image display device 1, and each means can exchange the processing results via the image area information 31 of the RAM 13.

  FIG. 5 is a schematic diagram for explaining the processing of the boundary extension means 51. The boundary extension processing is performed in order to make it possible to detect even when the end points (start point and end point) of the monochrome line region are present at the boundary of the input image in the monochrome line region detection processing described later. It is processing. The boundary expansion processing unit 51 adds two columns of color pixels on both sides of the input image in the line direction (lateral direction) (left and right of the input image) (see the hatched portion in FIG. 5). Then, a process of expanding the input image in the line direction is performed.

  FIG. 6 is a schematic diagram for explaining the processing of the monochrome line area detecting means 52. The monochrome line area detection unit 52 receives the input image expanded by the boundary expansion unit 51 for each pixel, and the input pixel is first given to the monochrome line candidate detection unit 53. The monochrome line candidate detection means performs processing for detecting a candidate for a monochrome line area composed of continuous monochrome pixels. First, from the pixel value of the input pixel, this pixel is a color pixel or a monochrome pixel. It is determined whether it is a pixel. For example, when each pixel has three values of RGB, a pixel in which R = G = B is determined to be a monochrome pixel, and the other pixels can be determined to be color pixels.

  Next, the monochrome line candidate detection means 53 detects the start point and end point (end point) of the candidate for the monochrome line area. In order to detect the start point and the end point, the monochrome line candidate detection unit 53 detects two consecutive pixels that are sequentially input (for example, two pixels of a pixel input at the present time and a pixel input at the previous time point). Pixel, hereinafter simply referred to as the previous pixel and the subsequent pixel). Note that the expansion of the input image by the boundary expansion unit 51 is performed in order to facilitate the check of two consecutive pixels performed by the monochrome line candidate detection unit 53.

  The monochrome line candidate detection means 53 detects the subsequent pixel as a starting point if the previous pixel is a color pixel and the subsequent pixel is a monochrome pixel. The monochrome line candidate detection means 53 detects the previous pixel as an end point if the previous pixel is a monochrome pixel and the subsequent pixel is a color pixel. Furthermore, the monochrome line candidate detection means 53 can detect the monochrome pixel as a start point or an end point if the monochrome pixel exists at the boundary of the input image. The monochrome line candidate detection unit 53 detects a region in which monochrome pixels from the detected start point to the end point are continuous as a candidate for the monochrome line region, and supplies the detected region to the start / end point check unit 54 and the color check unit 55.

  As will be described later, the monochrome line area candidate detected by the monochrome line candidate detection means 53 is determined by a predetermined threshold (hereinafter referred to as the area width) from the start point to the end point. Is larger than the first threshold value), it is determined as a monochrome line area by the start / end point check means 54. Further, when the determined monochrome line area exists in the first line of the input image, or exists in the next line of the line not including the monochrome line area, the image area information 31 is set as the start line area of the monochrome image area. be registered.

  FIG. 7 is a schematic diagram illustrating a configuration example of the image area information 31. The image area information 31 in the RAM 13 includes a 1-bit “valid flag”, a 1-bit “processing flag”, a 13-bit “X coordinate of the start point”, a 13-bit “Y coordinate of the start point”, and 13 bits. Information relating to the monochrome image area such as “X coordinate of end point” and “length of area” of 13 bits is stored. As the valid flag, a value of “1” is set for an image area determined as a valid monochrome image area as a result of the monochrome image area detection process. The processing flag is a flag indicating whether or not the monochrome image region is being detected, and the valid flag is set to “1” for the monochrome image region being processed.

  The X and Y coordinates of the start point are the X coordinate (the position in the horizontal direction (line direction) of the input image) and the Y coordinate of the start point of the monochrome line area determined as the start line area of the monochrome image area as described above. Coordinates (positions in the vertical direction (column direction) of the input image) are set. As the X coordinate of the end point, the X coordinate of the end point of the last monochrome line area of the monochrome image area is set. The length of the area is set to the length in the vertical direction of the monochrome image area (corresponding to the number of monochrome line areas included in the monochrome image area). When the start line region of the monochrome image region is detected, the processing flag of the image region information 31, the X coordinate of the start point, the Y coordinate of the start point, and the X coordinate value of the end point are set (and the valid flag is The initial value is set to 0, and the length of the area is set to 1 as the initial value).

  FIG. 8 is a schematic diagram for explaining the processing of the start / end point check means 54. The start / end point check means 54 of the monochrome line area detection means 52 determines whether the monochrome line area candidate detected by the monochrome line candidate detection means 53 is a monochrome line area following the start line area of the monochrome image area, or a new one. Processing is performed to determine whether the area is a monochrome line area corresponding to the start line area of the monochrome image area or not.

  The start / end point check means 54 compares the start point of the candidate for the monochrome line area with the X coordinate of the start point of the monochrome image area (having the processing flag of 1) set in the image area information 31, and the difference It is determined whether or not (the coordinate difference in the line direction) is within a threshold (hereinafter referred to as a second threshold). Similarly, the start / end point check means 54 compares the end point of the candidate for the monochrome line area with the X coordinate of the end point of the monochrome image area set in the image area information 31, and the difference is a threshold value (hereinafter referred to as “first”). It is determined whether it is within 3 thresholds).

  When the difference between the start point and end point of the candidate for the monochrome line area and the X coordinate of the start point and end point of the monochrome image area set in the image area information 31 are within the second threshold and the third threshold, respectively, The start / end point check means 54 determines that the candidate for the monochrome line area is a monochrome line area included in the compared monochrome image area, and updates the image area information 31 related to the monochrome image area. At this time, the start / end point check means 54 increases the value of the length of the area of the image area information 31 by one.

  If the difference between the start point or end point of the candidate for the monochrome line area and the X coordinate of the start point or end point of the monochrome image area set in the image area information 31 is not within the second threshold value or the third threshold value, start If the width of the candidate for the monochrome line area is equal to or greater than the first threshold, the end point check unit 54 determines that the line is a start line area for a new monochrome image area, and registers it in the image area information 31. Further, similarly, when there is no monochrome image area to be compared with the image area information 31, the start / end point check means 54 determines that a new monochrome image is obtained if the width of the candidate for the monochrome line area is equal to or larger than the first threshold value. It is determined that this is the start line area of the area, and registration in the image area information 31 is performed.

  FIG. 9 is a schematic diagram for explaining the processing of the color check means 55. The color check means 55 of the monochrome line area detection means 52 uses this area as a candidate for a monochrome line area even when a small number of color pixels are included in an area where monochrome pixels are continuous on one line. It is possible to treat as. When the width of the color pixel existing in the area where the monochrome pixels are continuous (the number of the continuous color pixels) is equal to or less than a threshold value (hereinafter referred to as the fourth threshold value), the color check unit 55 Candidate for

  The color check means 55 first compares the start point of the region where the monochrome pixels are continuous with the X coordinate of the start point of the monochrome image region set in the image region information 31, and the difference is within the second threshold. (This process is the same as the process of the start / end point check means 54). The color check means 55 determines whether the width of the area where the monochrome pixels are continuous is smaller than the width of the start line area of the monochrome image area set in the image area information 31. When the difference is within the second threshold and the width of the area is smaller than the width of the start line area, the color check means 55 performs the following color check process.

  In the color check process, the color check means 55 uses the next point after the end point of the continuous area of monochrome pixels as the start point of the color pixel area, and detects the end point of the continuous color pixel area from this start point. Thus, the width of the color pixel region is obtained. Next, if the width of the color pixel area is equal to or smaller than the fourth threshold, the color check means 55 ignores the color pixel area, detects the next end point of the monochrome pixel, and repeats the same processing. When the width of the color pixel area exceeds the fourth threshold value, the color check means 55 determines that the area where the monochrome pixels are continuous has ended, and the monochrome line area extends from the start point to the end point of this area including the color pixels. Candidate for The candidate for the monochrome line area by the color check means 55 becomes the processing target of the start / end point check means 54.

  In this way, information related to the monochrome line area detected by the monochrome line area detection unit 52 is sequentially stored in the image area information 31 of the RAM 13. A monochrome image region detection process by the monochrome image region detection unit 56 is performed each time the processing by the monochrome line region detection unit 52 is completed for each line of the input image.

  First, the monochrome image region detection unit 56 refers to the image region information 31 and determines whether or not the processing has been completed for the monochrome image region being processed by the monochrome line region detection unit 52 (processing flag is 1). Whether or not the processing has been completed can be determined based on whether or not the value of the width of the area of the image area information 31 has changed. Therefore, the monochrome image area detecting means 56 can detect each monochrome image area of the image area information 31. The value of the area width is copied in advance, and the latest value of the area width is compared with the copied value. When the latest value of the area width and the copy value have not changed, the monochrome image area detecting unit 56 determines that the process has been completed for the monochrome image area, and the image area is determined for the monochrome image area that has been determined to have ended. The processing flag of information 31 is set to 0.

  Next, the monochrome image area detecting means 56 refers to the image area information 31 and the area length of the monochrome image area determined to have been processed is equal to or greater than a threshold (hereinafter referred to as the fifth threshold) (that is, the first threshold). When monochrome line areas of 5 thresholds or more are adjacent to each other), it is determined that this monochrome image area is valid, and the valid flag is set to 1. A valid monochrome image area with the valid flag set to 1 is a detection result by the monochrome image area detection means 56.

  After all the lines of the input image are detected by the monochrome line area detecting means 52 and the detection by the monochrome image area detecting means 56 is finished, the image area adjusting means 57 adjusts (redetects) the monochrome image area. . 10 and 11 are schematic diagrams for explaining the processing of the image area adjustment unit 57. FIG. For example, when two monochrome image areas A and B are detected as shown in FIG. 10 as a result of detection by the monochrome image area detection unit 56, one or more lines (hatching) between the two monochrome image areas A and B are detected. There is a possibility that a region to be detected as a monochrome image region may be included in the portion marked with. This is the case, for example, when a monochrome line area is detected in this line, but it is not determined to be valid because the width of the area is less than the fifth threshold. In such a case, the image area adjustment unit 57 performs a process of adding a part of the line between the two monochrome image areas A and B to the monochrome image area A or B by adjusting the monochrome image area A or B. .

  First, the image area adjustment unit 57 refers to the image area information 31 in the RAM 13 and compares the X coordinates of the start points and the X coordinates of the end points of all the monochrome image areas determined to be valid. It is checked whether or not there is a monochrome image area where the coordinates match (however, a shift of about several pixels may be allowed). When there are two monochrome image areas in which the X coordinates of the start point or the end point (end point) coincide with each other, the image area adjustment unit 57 uses the Y coordinate of the end line of one monochrome image area and the other monochrome image area. The interval between the two monochrome image regions is checked from the Y coordinate of the start line, and it is determined whether or not this interval is equal to or less than a threshold value (hereinafter referred to as a sixth threshold value).

  When the interval between the two monochrome image areas is equal to or smaller than the sixth threshold, the image area adjustment unit 57 compares the widths of the two monochrome image areas in the horizontal direction (line direction), and the image of the monochrome image area having the smaller width is compared. The area information 31 is updated to include a part of the line between the two monochrome image areas. At this time, the image area adjustment unit 57 may update the Y coordinate of the start point of the image area information 31 or the value of the area length. For example, as shown in FIG. 11, the Y coordinate of the start point of the monochrome image region B can be moved upward so as to include a part of the line between the two monochrome image regions.

  The image processing unit 40 of the image display device 1 finishes the above-described monochrome image region detection processing on the input image from the PC 9 and then refers to the color region LUT 41 or monochrome image with reference to the image region information 31 that is the detection result. Processing for correcting the pixel value of each pixel of the input image is performed using the LUT 42 for use. In this correction processing, the image processing unit 40 performs correction using the monochrome LUT 42 for pixels included in the detected monochrome image area, and sets the color LUT 41 for pixels not included in the monochrome image area. The correction used may be performed. The image processing unit 40 displays the corrected image after completion of the correction processing.

  Next, processing performed by the image display apparatus 1 will be described using a flowchart. FIGS. 12 and 13 are flowcharts illustrating the procedure of the monochrome image region detection process performed by the image display apparatus 1, and are processes performed by the image processing unit 40 of the image display apparatus 1. First, the image processing unit 40 of the image display device 1 performs a process of extending the boundary of the input image by adding two columns of color pixels to both sides in the line direction of the input image by the boundary extending means 51 (step S1). S1).

  Next, the image processing unit 40 determines whether each pixel of the input image is a monochrome pixel or a color pixel by the monochrome line candidate detection unit 53 of the monochrome line area detection unit 52, and the monochrome pixels are continuously on the line. A process for detecting a candidate for a monochrome line region is performed by detecting the start point and end point of the region to be performed (step S2). Further, the image processing unit 40 includes a small number of color pixels by determining whether or not the width of the color pixels existing in the region where the monochrome pixels are continuous is equal to or smaller than the fourth threshold by the color check unit 55. A color check process for detecting a candidate for the monochrome line area is performed (step S3).

  Next, the image processing unit 40 uses the start / end point check means 54 to detect the start and end points of the detected monochrome line area candidate, and the start and end points of the monochrome image area set in the image area information 31. And whether or not each difference is within the second threshold value and the third threshold value, it is determined whether or not the candidate for the monochrome line region is an effective monochrome line region. A start / end point check process is performed to determine whether or not it is the start line area (step S4).

  From the result of the start / end point check process, the image processing unit 40 determines whether or not the monochrome line area candidate is the start line area (step S5), and if the monochrome line area candidate is the start line area. (S5: YES), information such as the coordinates of the start and end points is registered in the image area information 31 as the start line of a new monochrome image area (step S7), and the process proceeds to step S9.

  If the monochrome line area candidate is not the start line area (S5: NO), the image processing unit 40 determines whether the monochrome line area candidate is a valid monochrome line area (step S6). If the monochrome line area candidate is a valid monochrome line area (S6: YES), the image processing unit 40 updates the length of the area of the image area information 31 related to the corresponding monochrome image area (step S8). ), The process proceeds to step S9, and if the monochrome line area candidate is not a valid monochrome line area (S6: NO), the process proceeds to step S9 without updating the image area information 31.

  Next, the image processing unit 40 determines whether or not the processing of steps S2 to S8 has been completed for one line of the input image (step S9), and when the processing of one line has not been completed (S9: NO). The process is returned to step S2, and the above process is repeated until the process for one line is completed.

  When the processing of one line of the input image is completed (S9: YES), the image processing unit 40 causes the monochrome image area detecting unit 56 to have a number of effective line areas equal to or greater than the fifth threshold value based on the image area information 31. A monochrome image region detection process is performed in which a region adjacent to the line in the direction orthogonal to the line is detected as a monochrome image region (step S10). As a result of the monochrome image region detection process, the valid flag of the image region information 31 related to the valid monochrome image region is set to 1.

  Next, the image processing unit 40 determines whether or not the processing in steps S2 to S10 has been completed for all lines of the input image (step S11), and if the processing for all lines has not been completed (S11: NO) ), The process is returned to step S2, and the above-described process is repeated until the process for all lines is completed.

  When the processing of all the lines of the input image is completed (S11: YES), the image processing unit 40 uses the image area adjustment unit 57 for the number of lines equal to or less than the sixth threshold existing between the two monochrome image areas. An image area adjustment process for adding a part of the line to any monochrome image area is performed (step S12), and the process ends.

  FIG. 14 is a flowchart illustrating a procedure of image display processing performed by the image display device 1, and is processing performed by the image processing unit 40 of the image display device 1. The image processing unit 40 of the image display device 1 first reads the image area information 31 from the RAM 13 (step S21), and acquires the detection result of the monochrome image area.

  Next, the image processing unit 40 acquires one pixel of the input image given from the PC 9 (step S22), and determines whether or not this pixel is a pixel included in the monochrome image area of the image area information 31. Thus, it is determined whether or not this pixel is a monochrome pixel (step S23). When this pixel is a pixel in the monochrome image area (S23: YES), the image processing unit 40 performs a pixel value correction process using the monochrome LUT 42 (step S24), and proceeds to step S26. If this pixel is not a pixel in the monochrome image area (S23: NO), the image processing unit 40 performs a pixel value correction process using the color LUT 41 (step S25), and proceeds to step S26.

  Next, the image processing unit 40 determines whether or not the pixel value correction processing has been completed for all the pixels of the input image (step S26). If the pixel correction processing has not been completed (S26: NO) ), The process is returned to step S22, and the processes of steps S22 to S26 described above are repeated. When the correction process for all the pixels of the input image is completed (S26: YES), the image processing unit 40 performs a process of displaying the input image on the liquid crystal panel 19 (step S27), and ends the process.

  The image display device 1 having the above configuration determines whether each pixel of the input image from the PC 9 is a monochrome pixel, and the monochrome line area detection unit 52 is a monochrome pixel configured by monochrome pixels from each line of the input image. The line area is detected, and the monochrome image area detecting means 56 detects a monochrome image area composed of a plurality of monochrome line areas. Thereby, a monochrome image area composed of monochrome pixels can be detected from the input image. Also, a configuration for performing re-detection of the monochrome image area (adjustment of the monochrome image area by the image area adjustment means 57) for one or a plurality of lines existing between the two monochrome image areas detected by the monochrome image area detection means 56 By doing so, it is possible to redetect a monochrome image area that has not been detected due to the influence of characters or the like due to color pixels in the monochrome image area. By correcting the detected monochrome image area with the monochrome LUT 42 and correcting the other areas with the color LUT 41, the image display apparatus 1 can display the monochrome image included in the input image. The area and the color image area can be displayed with optimum display characteristics.

  Further, the monochrome line candidate detection means 53 detects a region in which a monochrome pixel continues in the line for the first threshold or more as a candidate for a monochrome line region, so that, for example, a small number of characters such as monochrome pixels written in the color image region. Thus, it is possible to prevent erroneous determination of an area formed by monochrome pixels as a monochrome line area.

  Further, the color check means 55 detects this area as a candidate for the monochrome line area even when the area where the monochrome pixels are continuous includes an area where the color pixels equal to or smaller than the fourth threshold value are included. Thus, for example, even when a color pixel character or the like is entered in the monochrome image area, the monochrome image area can be reliably detected.

  Further, the start / end point check means 54 is configured such that the deviation amount of the start point and end point of the monochrome line area candidate is within the second threshold value and the third threshold value with respect to the start point and end point of the start line area, respectively. In addition, a rectangular monochrome image region can be detected with high accuracy by using the monochrome line region candidate as an effective monochrome line region.

  Further, the monochrome image area detecting means 56 detects an area where the number of effective line areas equal to or greater than the fifth threshold is adjacent in the direction orthogonal to the line as an effective monochrome image area, thereby detecting an erroneously detected monochrome line area. It is possible to prevent the image area from being determined as an effective monochrome image area.

  Further, the image area adjusting means 57, when the start points or end points of the two monochrome image areas match and the number of lines between the two monochrome image areas is less than or equal to the sixth threshold value, By adjusting (redetecting) the monochrome image area for one or a plurality of lines, it is possible to relieve lines that were not included in the monochrome image area due to erroneous determination. The image area adjustment unit 57 adds a part of the line between the two effective image areas to the monochrome image area having the smaller size in the line direction of the two monochrome image areas to form a new monochrome image area. Accordingly, the possibility that inappropriate pixels (color pixels) are added to the monochrome image region can be reduced as compared with the case where a part of the line is added to the monochrome image region having a larger size in the line direction.

  In addition, since the processing for detecting the monochrome image area from the input image is performed by the image display device 1 instead of the PC 9, it is not necessary to install application software for monochrome image area detection on the PC 9 and image display is performed. Appropriate image display can be performed only by the apparatus 1. However, the monochrome image area detection processing may be performed by the PC 9 and the processing result may be supplied from the PC 9 to the image display device 1. Further, the image corrected by the color LUT 41 and the monochrome LUT 42 by the PC 9 is an image. It is good also as a structure input into the display apparatus 1. FIG.

  In the present embodiment, the image display device 1 is configured to perform a process of detecting a monochrome image region from the input image. However, the present invention is not limited to this, and a configuration of detecting a color image region from the input image. It is good. In addition, the detection target is not limited to a monochrome image area or a color image area. For example, the detection target is distinguished by other specific conditions, such as a red single color image area, an image area composed of pixels with luminance or chromaticity within a predetermined range, and the like. It may be an image area.

  In addition, although the image processing unit 40 of the image display device 1 performs the detection of the monochrome image region and the pixel value correction processing, the configuration is not limited to this, and the configuration performed by the control unit 11 of the image display device 1. It is good. In the case of this configuration, processing such as monochrome image region detection and pixel value correction processing is realized as one process of the control program 21 (computer program), and the control unit 11 executes the control program 21 so that the processing shown in FIG. The illustrated boundary expansion means 51 to image area adjustment means 57 are realized as software function blocks. Further, these processes may be performed by the PC 9 and the image display device 1 may directly display the image signal input from the PC 9. In the case of this configuration, the PC 9 is preinstalled with a computer program (for example, as a device driver) for performing these processes, and the PC 9 executes the computer program, whereby the boundary extension means 51 to the image area shown in FIG. The adjusting means 57 is realized as a software functional block in the PC 9.

1 Image display device 9 PC
11 Control unit 12 ROM
13 RAM
DESCRIPTION OF SYMBOLS 14 Backlight drive part 15 Liquid crystal drive part 16 Operation part 17 Image input part 18 Backlight 19 Liquid crystal panel 21 Control program 31 Image area information 40 Image processing part (Effective pixel determination means, effective line area detection means, effective image area detection means , Re-detection means)
41 color LUT
42 Monochrome LUT
51 Boundary extension means 52 Monochrome line area detection means (effective pixel determination means, effective line area detection means)
53 Monochrome line candidate detection means 54 Start / end point check means 55 Color check means 56 Monochrome image area detection means (effective image area detection means)
57 Image area adjustment means (re-detection means)

Claims (7)

In an image display device that displays an input image composed of a plurality of lines each including a predetermined number of pixels,
Effective pixel determining means for determining whether each pixel in the input image is an effective pixel that satisfies a specific condition;
Effective line area detecting means for detecting an effective line area composed of a plurality of effective pixels from each line in the input image;
Effective image area detecting means for detecting an effective image area composed of a plurality of effective line areas adjacent in a direction orthogonal to the line from the input image , and
If each pixel in the input image is included in the effective image region detected by the effective image area detecting means, Ri Citea to be displayed in display characteristics associated with the effective image area,
The effective line area detecting means includes
The effective line area included in the next line of the line that does not include the first line or the effective line area of the input image as a start line area,
An image display device characterized by detecting, as an effective line area, an area in which a coordinate difference in a line direction with respect to an end point of the start line area is within a predetermined value for lines after the line including the start line area . The effective line area detecting means includes
The image display device according to claim 1, wherein an area on a line in which a predetermined number or more of effective pixels are continuous is detected as an effective line area. Even when a region on a line where effective pixels are continuous includes a region where pixels other than a predetermined number of effective pixels are continuous, the region is detected as an effective line region.
The image display device according to claim 1, wherein: The image according to any one of claims 1 to 3, wherein the effective image area detecting means detects an area including a predetermined number or more of effective line areas as the effective image area. Display device. The effective pixel determination means determines an effective pixel according to whether each pixel is a monochrome pixel or a color pixel. The image display apparatus as described in any one. In an image region detection method for detecting an image region composed of pixels satisfying a specific condition from an image composed of a plurality of lines each including a predetermined number of pixels,
It is determined whether each pixel in the image is an effective pixel that satisfies a specific condition,
From each line in the image, to detect an effective line area composed of a plurality of effective pixels,
From the image, the detection of an effective image area composed of a plurality of effective line areas adjacent in the direction orthogonal to the line,
When detecting the effective line area, the effective line area included in the next line of the first line of the image or the line not including the effective line area is set as the start line area, and the lines after the line including the start line area A method for detecting an image area , wherein an area where a coordinate difference in a line direction with respect to an end point of the start line area is within a predetermined value is detected as an effective line area . In a computer program for causing a computer to detect an image region composed of pixels satisfying a specific condition from an image composed of a plurality of lines each including a predetermined number of pixels,
An effective pixel determination step for causing a computer to determine whether each pixel in the image is an effective pixel that satisfies a specific condition;
An effective line area detecting step for causing a computer to detect an effective line area composed of a plurality of effective pixels from each line in the image;
An effective image area detecting step for causing the computer to detect an effective image area composed of a plurality of effective line areas adjacent in a direction orthogonal to the line from the image, and
In the effective line area detecting step, the effective line area included in the next line of the first line of the image or the line not including the effective line area is set as a start line area, and the lines after the line including the start line area, A computer program for causing an area in which a coordinate difference in a line direction with respect to an end point of the start line area is within a predetermined value to be detected as an effective line area .

Images