JP5997019B2 - Display control apparatus, display control method, and display control program - Google Patents

Description

  The present invention relates to a display control device, a display control method, and a display control program, and more particularly to a display control device, a display control method, and a display control program for controlling a display device capable of independently controlling color gradation and luminance. .

  In order to obtain a wide dynamic range and gradation information, an HDR (High Dynamic Range) image in which a plurality of photographs taken at different exposures by changing the exposure time is known.

  However, in a general display, the amount of information that can be expressed for each color of RGB is about 8 bits, so an image such as an HDR image with more color gradation information cannot be expressed. Therefore, in order to display the input image on a display having a lower dynamic range, the output image is generated by compressing the dynamic range of the input image.

  As an example of a method for compressing the dynamic range, there is a method called a local dimming method. This method is effective in a liquid crystal display that can be controlled for each area of the backlight. By changing the brightness of the backlight for each area of the image to be displayed, the image as a whole is more than the gradation expression of the liquid crystal display This is a method for realizing the gradation expression.

  However, this method requires a special and expensive material for the light guide plate of the backlight or the like, and the luminance cannot be changed in a small liquid crystal display in which the location and number of the backlight light sources are limited.

  As another method, there is a method of using a tone curve that is a curve representing the gradation value of the output image for each gradation value of the input image. As an example, there is a method of simply compressing the dynamic range of an input image by reducing the slope of the tone curve of the entire image. This is to make the gradation value of the entire output image uniformly smaller than the gradation value of the input image, and the contrast of the output image is lowered. As a result, the quality of the output image is reduced.

  As another method using the tone curve, there is a method in which the input image is divided into a plurality of regions for each feature region (bright portion / dark portion, background / person, etc.), and the tone curve applied to each region is changed. Can be mentioned. In this method, although the gradation of the entire input image is reproduced as much as possible in the output image, the lightness and darkness relationship of the input image may be reversed on the output image, and realism may be impaired.

  In order to solve this problem, Japanese Patent Laid-Open No. 2009-246510 (hereinafter referred to as Patent Document 1) compresses and outputs the dynamic range of an input image in order to display an image on a display having a lower dynamic range than the original data. An image processing method for creating an image is disclosed. In the method of Patent Document 1, first, an observation condition for an output image is acquired, and a visual field size in the output image is calculated based on the observation condition. Then, for each pixel of the input image, the white level of the neighboring region corresponding to the visual field size is calculated, and the gain coefficient is calculated based on the white level. Based on this gain coefficient, gain adjustment is performed for each pixel of the input image. Clipping is performed for pixels whose luminance exceeds a predetermined value. Thereby, the dynamic range of the output image can be adaptively changed for each pixel.

  Japanese Patent Application Laid-Open No. 2007-228048 (hereinafter, Patent Document 2) also discloses a method of compressing a dynamic range as a method of changing the dynamic range on display of an image displayed on a display unit. The method of Patent Literature 2 displays a histogram indicating the luminance distribution of the original image superimposed on the image, and accepts an operation for designating an arbitrary position on the displayed histogram from the user. A second luminance level is set. In the set range of the first and second luminance levels, gradation correction processing for changing the dynamic range on display of the image is performed, and the image subjected to the gradation correction processing is displayed.

JP 2009-246510 A JP 2007-228048 A

  However, in the method of Patent Document 1 described above, although gradation reduction is reasonably expressed by clipping processing, a reduction in contrast can be suppressed, but a part of the original image information is completely lost, and therefore based on the missing information. There is a problem that the image is not displayed. In addition, there is also a problem that the entire process can be accommodated in one field of view and effective processing is difficult, especially when the field of view of a small-sized display device such as a display device mounted on a portable terminal is used.

  Moreover, since the method of the above-mentioned patent document 2 requires the operation by a histogram, it is difficult for a user who does not have knowledge about the histogram to understand intuitively, and the above adjustment work may be difficult. There is a problem. In particular, in the case of a display device of a small size such as a display device mounted on a mobile terminal, a part of the screen is occupied by the user interface using the histogram, and the visibility of the user is deteriorated. There is also a problem that the work is difficult.

  The present invention has been made in view of such problems, and displays a high-quality output image with an easy operation when displaying an output image in which the dynamic range of the input image is compressed on a display device. It is an object of the present invention to provide a display control device, a display control method, and a display control program.

  In order to achieve the above object, according to one aspect of the present invention, the display control device performs control for displaying an image based on an input image on a display device whose color gradation and luminance are independent control targets. An illuminance acquisition means for acquiring a measurement result of illuminance around the display device, and based on a relationship in which gradation values of color gradations of an input image are defined in advance based on the illuminance The range in which the change is not lost by the conversion is set as the first range, and the range other than the first range of the color gradation of the input image is converted into a predetermined gradation value with a predetermined gradation value. Then, a setting unit for setting the second range in which the change is lost and a luminance control unit for controlling the luminance of the display device so that the luminance is in accordance with the illuminance are provided. When the illuminance is brighter than the predetermined reference illuminance, the setting means changes the first range stepwise toward the brighter side than the predetermined reference range, and when the illuminance is darker than the reference illuminance, The range of 1 is changed stepwise from the reference range to the dark side. In addition, the luminance control means increases the luminance of the display device above a predetermined reference luminance when the illuminance is brighter than the reference illuminance, and sets the luminance of the display device when the illuminance is darker than the reference illuminance. Lower than brightness.

  Preferably, the setting unit sets a range of a specified gradation value including a gradation value having a frequency higher than the specified frequency in the input image as a reference range, and an amount of change according to a difference of the illuminance from the reference illuminance. The second range is changed from the reference range.

  Preferably, the luminance control means changes the luminance of the display device from the reference luminance at a change rate defined according to the reference illuminance.

  According to another aspect of the present invention, the display control method is a control method for displaying an image based on an input image on a display device whose color gradation and brightness are independent control targets, A step of obtaining a measurement result of the illuminance, and a range in which the change is not lost by converting the gradation value of the color gradation of the input image based on a predetermined relationship based on the illuminance. A range other than the first range of the color gradation of the input image is set as a second range that loses the change by converting the gradation value into a predetermined gradation value. And a step of controlling the luminance of the display device so that the luminance is in accordance with the illuminance. In the setting step, when the illuminance is brighter than the predetermined reference illuminance, the first range is gradually changed to the brighter side than the predetermined reference range, and when the illuminance is darker than the reference illuminance, The first range is changed stepwise from the reference range to the dark part side. Further, in the step of controlling the luminance, when the illuminance is brighter than the reference illuminance, the luminance of the display device is set higher than a predetermined reference luminance, and when the illuminance is darker than the reference illuminance, the luminance of the display device is set as a reference. Lower than brightness.

  According to still another aspect of the present invention, a display control program is a program for causing a computer to execute a process of displaying an image based on an input image on a display device whose color gradation and luminance are independent control targets. The step of obtaining the measurement result of the illuminance around the display device and the change of the gradation value of the color gradation of the input image based on the illuminance based on a predetermined relationship are lost. The non-applicable range is set as the first range, and the range other than the first range of the color gradation of the input image is converted into a predetermined gradation value that is defined in advance, and the change is lost. The step of setting the second range and the step of controlling the luminance of the display device so that the luminance is in accordance with the illuminance are executed by the computer. In the setting step, when the illuminance is brighter than the predetermined reference illuminance, the first range is gradually changed to the brighter side than the predetermined reference range, and when the illuminance is darker than the reference illuminance, The first range is changed stepwise from the reference range to the dark part side. Further, in the step of controlling the luminance, when the illuminance is brighter than the reference illuminance, the luminance of the display device is set higher than a predetermined reference luminance, and when the illuminance is darker than the reference illuminance, the luminance of the display device is set as a reference. Lower than brightness.

  According to the present invention, when an output image obtained by compressing the dynamic range of an input image is displayed on a display device, a high-quality output image can be displayed with an easy operation.

It is a figure which shows the specific example of a structure of the terminal device concerning embodiment. It is a figure showing the outline | summary of the display control in a terminal device. It is a block diagram which shows the specific example of a function structure of a terminal device. It is a figure for demonstrating the setting method of a change area | region. It is a figure for demonstrating the change of a change area | region. It is a figure for demonstrating the change of a change area | region. It is a flowchart showing the flow of the display control in a terminal device. It is a figure for demonstrating the change of a change area | region in 2nd Embodiment. It is a figure for demonstrating the setting of a change area | region in 3rd Embodiment. It is a figure for demonstrating the setting of a change area | region in 4th Embodiment. It is a figure for demonstrating the setting of a change area | region in 4th Embodiment.

  Embodiments of the present invention will be described below with reference to the drawings. In the following description, the same parts and components are denoted by the same reference numerals. Their names and functions are also the same. Therefore, these descriptions will not be repeated.

[First Embodiment]
<Device configuration>
FIG. 1 is a diagram illustrating a specific example of a configuration of a terminal device 100 as an example of a display control device according to the present embodiment.

  In the following description, as shown in FIG. 1, it is assumed that the display control device itself includes a display device. However, the display control device may be a device separate from the display device, and may be electrically connected to the display device by wire or wireless to control the display. The terminal device 100 may be any device as long as it is equipped with a display device that can individually control color gradation and luminance, as typified by a general liquid crystal display. For example, a small notebook personal computer (personal computer), a game machine, a document browsing device, a portable TV (television receiver), and the like can be given. Further, the display control device is not limited to the portable terminal, and may be another device as long as it controls a display device that can individually control color gradation and luminance. For example, a personal computer or a TV is applicable.

  Referring to FIG. 1, terminal apparatus 100 stores a control unit 10 for controlling the entire apparatus including a CPU (Central Processing Unit) as a configuration of the display control apparatus, a program executed by the CPU, and the like. A main storage unit 11 including a ROM (Read Only Memory) and a RAM (Random Access Memory) serving as a work area of the CPU, and a sub storage unit 12 including a memory for storing image data and the like , An input device 13 such as a switch, and a photometry unit 14 for measuring illuminance. Furthermore, in the present embodiment, the terminal device 100 includes the display device 15 as an example in which the display control device includes the display device itself to be controlled.

  The photometry unit 14 is an example of a mechanism for acquiring the illuminance around the display device 15 and corresponds to, for example, an illuminance sensor. The function for acquiring the illuminance around the display device 15 is not limited to the photometry unit 14, and may be a mechanism that receives an input of the result of illuminance measurement in another device. For example, when the display control device is a device separate from the display device, a photometric unit or the like is provided as a mechanism for measuring illuminance on the display device side, and the display control device receives the measurement result of illuminance from the display device. Input may be accepted.

  The display device 15 includes a display unit (for example, a liquid crystal panel portion) 15a and a light control unit (for example, a backlight portion) 15b that is a light source, and each is independently controlled by the control unit 10.

<Overview of operation>
The terminal device 100 which is a display control device according to the present embodiment performs processing for generating an output image by compressing the dynamic range of an input image (HDR (High Dynamic Range) image) having a wide dynamic range, and outputs the output image. Is displayed on the display device 15.

  At this time, if the dynamic range of the input image is simply compressed, the contrast of the output image is lowered and the image quality is lowered.

  In view of this, the terminal device 100 according to the present embodiment uses a gradation area having a predetermined data amount (hereinafter referred to as a change area) in each gradation of the input image in the input image in order to suppress a decrease in contrast. In other words, the remaining area (hereinafter referred to as a non-change area) is set as an area where the gradation change of the input image is eliminated by replacing the gradation value with a specified gradation value. The non-change area having a higher gradation value than the change area of the gradation of the input image is replaced with a predetermined high gradation value such as white, and the non-change area having a lower gradation value than the change area is, for example, black. By changing to a low tone value defined in advance, the change in the tone value of these regions is lost. As a result, in the output image, only the gradation information indicating the change in the gradation value in the change area remains among the gradation information indicating the change in the value of each gradation in the input image, and the change in the gradation value in the non-change area is left. The gradation information representing is compressed.

  Then, the terminal device 100 shifts the change region according to the illuminance around the display device 15. FIG. 2 is a diagram illustrating an outline of display control in the terminal device 100.

  Referring to FIG. 2, when the illuminance is low (dark) from the normal illuminance environment shown in the center (step S1), terminal apparatus 100 shifts the change area to the dark part side. As a result, among the color gradations of the displayed output image, the color gradation on the dark side is expressed.

  On the other hand, when the illuminance is changed from a normal illuminance environment to a high (bright) illuminance environment (step S2), the terminal device 100 shifts the change area to the bright part side. As a result, among the color gradations of the output image to be displayed, the color gradation on the bright side is expressed.

  When returning from a low illuminance environment to a normal illuminance environment (step S3) and when returning from a high illuminance environment to a normal illuminance environment (step S4), the terminal device 100 restores the change area.

  However, the image quality of the output image is lowered simply by shifting the change area. For example, if the change area is simply shifted to the dark side, the non-change area having a high gradation value is increased in the output image as compared with the change area. Will increase. As a result, the output image appears as if the entire image is bright, and a dark feeling does not appear dark. On the other hand, when the shift is performed, so-called blackout increases, which is the same.

  Therefore, the terminal device 100 shifts the change region as described above, and also changes the luminance of the light control unit 15b that is a backlight. That is, in the case of step S1, the terminal device 100 shifts the change area to the dark part side and decreases the luminance of the light control part 15b. In the case of step S2, the terminal device 100 shifts the change area to the bright part side and increases the luminance of the light control part 15b.

  As a result, even when the change area is shifted as described above and the ratio of the high gradation value in the output image is increased, the display device 15 itself is reduced in luminance so that dark objects appear dark. It will look like. Even if the brightness is reduced in this way, the gradation expression on the display screen can be recognized on the same principle that the iris of the human eye opens under dark illuminance and the sensitivity to dark areas is improved. It becomes possible. The reverse is also true.

<Functional configuration>
FIG. 3 is a block diagram illustrating a specific example of a functional configuration of the terminal device 100 for performing the above control. Each function shown in FIG. 3 is formed mainly on the CPU by reading and executing the program stored in the main storage unit 11 by the CPU of the control unit 10. The unit may be realized by the apparatus configuration shown in FIG.

  With reference to FIG. 3, the control unit 10 of the terminal device 100 receives an illuminance measurement result input from the photometry unit 14 and obtains an illuminance measurement unit 101 for obtaining an illuminance measurement result around the display device 15. The setting unit 102 for setting a change area (and non-change area) of the color gradation of the input image based on the illuminance around the display device 15, and each of the set change area and non-change area An image signal processing unit 103 for performing processing for generating an output image by converting gradation values, a display control unit 104 for performing processing for displaying the output image on the display unit 15a of the display device 15, and illuminance And a dimming control unit 105 for controlling the luminance of the dimming unit 15b of the display device 15 so that the luminance is in accordance with the above.

  FIG. 4 is a diagram for explaining a method for setting a change area in the setting unit 102. In FIG. 4, the dotted curve displayed superimposed on the tone curve represents the histogram of the input image. In FIG. 4, an example is shown in which a tone curve is used in which the brightness (gradation value) increases (becomes brighter) from left to right on the horizontal axis and from bottom to top on the vertical axis. May be. Further, the tone curve of each color channel may be used. The same applies to the following examples.

  With reference to FIG. 4, as an example of a method for setting a change area in setting unit 102, a method using a histogram can be cited. That is, the setting unit 102 represents an appearance frequency for each gradation value of the input image as a histogram, and the appearance frequency is an area higher than a specified frequency stored in advance as a threshold value, and has a predetermined range. Is set as the change area. Alternatively, the setting unit 102 may set, as the change area, an area in a predetermined range that includes gradation values with a frequency higher than the specified frequency. Alternatively, the setting unit 102 uses the differential value and is a region where the change rate of the appearance frequency is larger than the change rate stored in advance as a threshold value, and a region in a predetermined range is used as the change region. It may be set.

  5 and 6 are diagrams for explaining the change of the change area in the setting unit 102. FIG. In FIGS. 5 and 6, the tone curve before the change region is changed is indicated by a dotted line, and the tone curve after the change is indicated by a solid line.

  Referring to FIGS. 5 and 6, setting unit 102 is located closer to the brighter side than a change region (hereinafter referred to as a reference region) in which a change region is defined in advance when the illuminance is brighter than a predetermined reference illuminance. It is changed stepwise (FIG. 5), and when it is darker than the reference illuminance, it is changed stepwise to the dark part side (FIG. 6).

  The image signal processing unit 103 substitutes the gradation value x of the change area in the color gradation of the input image into the function y = F (x) stored in advance, so that the gradation value x of the input image is obtained. On the other hand, it is converted into a gradation value y having a rate of change having a predefined relationship. For example, when the function F (x) is a × x + b and the coefficient a = 1 indicating the rate of change is set, the tone value y of the output image maintaining the rate of change of the tone value x can be obtained. In the example of FIGS. 5 and 6, the function F (x) represents a straight line as described above (straight line function), and the gradation value x of the input image is converted at a predetermined constant change rate a. It is supposed to be. However, the function F (x) for converting the tone value x of the input image is not only a linear function but also converted when the tone value x of the input image changes, such as a curve (for example, a gamma curve) or a combination of a curve and a straight line. Any function may be used as long as the change in the tone value of the input image and the change in the tone value of the output image corresponding to the later tone value y change. The function F (x) includes all these functions.

  Further, the image signal processing unit 103 converts the gradation value of the non-change area into a predetermined constant gradation value. That is, the image signal processing unit 103 replaces the gradation value of the non-change area having a higher gradation value than the change area of the non-change area with a predetermined high gradation value such as white. Further, the image signal processing unit 103 replaces the gradation value of the non-change area having a lower gradation value than that of the change area with a predetermined low tone value such as black.

  As a result, the output image retains the color gradation of the change area in the entire color gradation of the input image, and loses the color gradation of the other areas (non-change areas). That is, the dynamic range of the input image is compressed to the dynamic range corresponding to the change region.

  The dimming control unit 105 sets the luminance of the dimming unit 15b to be higher than a predetermined reference luminance when the illuminance is brighter than the reference illuminance, and lower than the reference luminance when darker than the reference illuminance. For example, the dimming control unit 105 calculates the amount of change in luminance according to the difference between the measurement result of the illuminance around the display device 15 and the reference illuminance. The coefficient used for the calculation may be set corresponding to the reference illuminance. As a result, the brightness becomes higher (brighter) as it becomes brighter than the reference illuminance, and the brightness becomes lower (darker) as it becomes darker than the reference illuminance. The dimming control unit 105 may change a predetermined change amount and luminance.

<Operation flow>
FIG. 7 is a flowchart showing the flow of display control in terminal apparatus 100 according to the present embodiment. The control shown in the flowchart of FIG. 7 is realized by causing the CPU of the control unit 10 to read out and execute a program stored in the main storage unit 11 to exhibit each function of FIG.

  Referring to FIG. 7, the display control in terminal apparatus 100 mainly includes a process for setting a reference value (step # 1) and a process for compressing the dynamic range (step # 2). Specifically, as processing for setting a reference value (step # 1), the CPU measures illuminance at the time of setting and sets the measurement result as reference illuminance (step S101).

  The CPU stores in advance a parameter that is a coefficient for changing the luminance with respect to the reference illuminance, and sets the coefficient according to the reference illuminance set in step S101 with reference to the correspondence (step S103). .

  Next, the CPU generates a histogram of the input image (step S105), and sets a range where the appearance frequency is equal to or higher than the threshold value or a range where the change in the appearance frequency is equal to or higher than the threshold value to the reference position ( Hereinafter, the reference area is set (step S107).

  The above is the process for setting the reference value. In the example of FIG. 7, it is assumed that a process for setting a reference value is performed for each series of operations. However, a reference illuminance (step S101), a coefficient of luminance change (step S103), a reference area (step S107), and the like. ) May be stored in advance in association with the input image, or may be set in the input image itself. Further, the terminal device 100 may store the value set by performing the processing of steps S101 to S107 once in association with the input image.

  Next, as a process of compressing the dynamic range (step # 2), the CPU measures the illuminance around the display device 15 (step S109) and compares it with the set reference illuminance.

  When the measurement result of the illuminance around the display device 15 is the same as the reference illuminance or within a predetermined range that can be said to be the same as the reference illuminance (YES in step S111), the CPU sets the change area of the set reference area. The brightness of the dimming unit 15b is also kept at the brightness defined in advance as the reference brightness (step S113).

  On the other hand, if the measurement result of the illuminance around the display device 15 is brighter than the reference illuminance (YES in step S115), the CPU moves the change area set as the reference area to the bright part by a predetermined amount. After that, the gradation value of the input image is converted (step S117). Further, the luminance of the dimming unit 15b is set to be higher than the luminance defined in advance as the reference luminance by an amount corresponding to the coefficient set in step S103 (step S119).

  On the other hand, when the measurement result of the illuminance around the display device 15 is darker than the reference illuminance (NO in step S115), the CPU moves the change area set as the reference area to the dark side by a predetermined amount. After that, the gradation value of the input image is converted (step S121). In addition, the luminance of the dimming unit 15b is set to be lower than the luminance preliminarily defined as the reference luminance by an amount corresponding to the coefficient set in step S103 (step S123).

  The CPU may display the output image after conversion on the display unit 15a as the process of compressing the dynamic range (step # 2) (step S127). Preferably, the CPU confirms whether the brightness represented by the converted gradation value is within a brightness range that can be displayed on the display unit 15a stored in advance. As a result, if it is not within the displayable range (NO in step S125), the CPU displays an error (step S129). At this time, the CPU may display the input image that is not converted together with the error display as it is, or may display the output image that has been converted to a gradation value corresponding to the displayable brightness.

<Effect of Embodiment>
By performing the above display control in the terminal device 100 according to the present embodiment, an output image is generated in consideration of the optical characteristics of the human eye. For this reason, the output image with the compressed dynamic range is visually recognized as an image having a dynamic range greater than the amount of information that can be displayed on the display unit 15a such as a liquid crystal display with fine gradation. That is, gradation can be expressed in a wider dynamic range by dynamically changing the range (change area) expressed in the output image of the color gradation of the input image according to the ambient illuminance. . Therefore, the quality of the output image can be improved while compressing the dynamic range.

  Further, by performing the above display control, for example, as shown in FIG. 2, the terminal device 100 can display the display device 100 with an intuitive and easy operation of brightly illuminating or darkening the terminal device 100 itself. The display of 15 switches. Therefore, specialized knowledge such as a histogram is not required for switching the display, and the operation can be performed intuitively. Further, since it is not necessary to display a UI for switching display such as a histogram on the display, even a small display device such as a mobile phone can be easily operated.

[Second Embodiment]
FIG. 8 is a diagram for explaining the change of the change region in the second embodiment as another example. The amount (shift amount) for changing the change region may be a fixed amount. As another example, the amount may not be constant. For example, it may be an amount corresponding to the difference between the measurement result of the illuminance around the display device 15 and the reference illuminance. For example, it may be an amount corresponding to the gradation value of the input image.

  FIG. 8 shows the latter example, and the terminal device 100 according to the second embodiment may determine the shift amount according to the appearance frequency of the gradation value of the input image. As an example, the shift amount may be increased in the range of gradation values where the appearance frequency is less than or equal to the predetermined frequency, and the shift amount may be decreased in the range where the appearance frequency is greater than or equal to the predetermined frequency.

  Alternatively, the terminal device 100 according to the second embodiment may change the range of the change area after moving the range according to the appearance frequency of the gradation value of the input image to be moved. As an example, the change area may be widened when the appearance frequency of the gradation value of the input image to be moved is equal to or higher than a predetermined frequency, and the change area may be narrowed when the frequency is lower than the predetermined frequency.

In this way, the gradation can be displayed more finely.
[Third Embodiment]
FIG. 9 is a diagram for explaining setting of a change area in the third embodiment as another example. As illustrated in FIG. 9, the terminal device 100 may set a plurality of change areas according to the appearance frequency of the gradation value of the input image. Further, when moving the change area, a plurality of change areas may be combined according to the amount of movement, or one change area may be separated.

  Note that, as shown in FIG. 9, the gradation value conversion rate may be changed according to the appearance frequency of the gradation value of the input image. In the example of FIG. 9, when the appearance frequency of the gradation value of the input image is equal to or higher than the predetermined frequency, conversion is performed so that the reproduction rate is high (part A), and the appearance frequency of the gradation value of the input image is the predetermined frequency. In the following cases, conversion may be performed so that the gradation value becomes smaller as a whole (B portion).

[Fourth Embodiment]
The terminal device 100 according to the fourth embodiment as another example analyzes an input image and extracts a feature region including a person, a person's face, a building, and the like, and a gradation corresponding to each feature region The characteristic area may be included in the change area by weighting the range of values.

  10 and 11 are diagrams for explaining the setting of the change area in the fourth embodiment. FIG. 10 shows an input image, and FIG. 11 shows a histogram thereof.

  The image of FIG. 10 includes a building, a person, and a person's face. When this image is an input image, the terminal device 100 analyzes the input image and extracts a region including these as a feature region. For this analysis, for example, techniques such as pattern recognition and edge detection can be used. The terminal device 100 specifies the gradation values of these areas.

  Referring to FIG. 11, terminal apparatus 100 groups and weights the range of gradation values included in the feature region of each feature region in the histogram of the input image.

  For example, when there are a plurality of gradation value ranges for a feature region of a building, the terminal device 100 associates the plurality of ranges as a group of gradation value ranges for the feature region of the building. The same applies to other feature regions. Then, the terminal device 100 allows the gradation value range of the same group to be either the change region or the non-change region, that is, part of the gradation value range of the same group is the change region. It is compared with the grouped gradation value ranges when setting the change region so that the other part does not belong to the non-change region.

  As a result, when switching images according to illuminance, it is possible to prevent a situation in which only some color gradations are expressed and other color gradations are not expressed for the same feature region, and deterioration in quality is suppressed. Can do.

[Fifth Embodiment]
In the above example, the terminal device 100 sets (moves) the change area each time according to the measurement result of the illuminance. As another example, the terminal device according to the fifth embodiment is used. 100 prepares output images of three patterns in advance from an input image, a high illumination image (bright part weighted image), a low illumination image (dark part weighted image), and a standard illumination (standard image). Depending on the result, a corresponding output image may be displayed promptly.

  Thereby, the process in the terminal device 100 can be facilitated. Further, it is possible to prevent the images from being switched finely in an environment where the change in illuminance state is severe.

[Sixth Embodiment]
Furthermore, it is possible to provide a program for causing a display control device such as the terminal device 100 to execute the above-described control. Such a program is recorded on a computer-readable recording medium such as a flexible disk attached to the computer, a CD-ROM (Compact Disk-Read Only Memory), a ROM, a RAM, and a memory card, and provided as a program product. You can also. Alternatively, the program can be provided by being recorded on a recording medium such as a hard disk built in the computer. A program can also be provided by downloading via a network.

  The program according to the present invention is a program module that is provided as a part of a computer operating system (OS) and calls necessary modules in a predetermined arrangement at a predetermined timing to execute processing. Also good. In that case, the program itself does not include the module, and the process is executed in cooperation with the OS. A program that does not include such a module can also be included in the program according to the present invention.

  The program according to the present invention may be provided by being incorporated in a part of another program. Even in this case, the program itself does not include the module included in the other program, and the process is executed in cooperation with the other program. Such a program incorporated in another program can also be included in the program according to the present invention.

  The provided program product is installed in a program storage unit such as a hard disk and executed. The program product includes the program itself and a recording medium on which the program is recorded.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  DESCRIPTION OF SYMBOLS 10 Control part, 11 Main memory part, 12 Secondary storage part, 13 Input device, 14 Photometry part, 15 Display apparatus, 15a Display part, 15b Light control part, 100 Terminal device, 101 Illuminance acquisition part, 102 Setting part, 103 Image Signal processing unit, 104 display control unit, 105 dimming control unit.

Claims (5)

A control device that performs control for displaying an image based on an input image on a display device whose color gradation and luminance are independent control targets,
Illuminance acquisition means for acquiring measurement results of illuminance around the display device;
Based on the illuminance, a range that does not lose its change by converting a gradation value of the color gradation of the input image based on a predetermined relationship is set as the first range, and the input Setting means for setting a range other than the first range of the color gradation of the image as a second range in which the change is lost by converting the gradation value into a predetermined gradation value;
A luminance control means for controlling the luminance of the display device so as to have a luminance according to the illuminance,
The setting means, when the illuminance is brighter than a predetermined reference illuminance, gradually changes the first range to a brighter side than the predetermined reference range, and the illuminance is higher than the reference illuminance. In the case of darkness, the first range is gradually changed to the dark side of the reference range,
The luminance control means increases the luminance of the display device above a predetermined reference luminance when the illuminance is brighter than the reference illuminance, and when the illuminance is darker than the reference illuminance, A display control device that lowers the luminance below the reference luminance.   The setting means sets a specified gradation value range including a gradation value with a frequency higher than a specified frequency in the input image as the reference range, and changes the illuminance according to a difference from the reference illuminance. The display control apparatus according to claim 1, wherein the second range is changed from the reference range by an amount.   The display control device according to claim 1, wherein the luminance control unit changes the luminance of the display device from the reference luminance at a change rate defined according to the reference illuminance. A control method for displaying an image based on an input image on a display device whose color gradation and brightness are independent control targets,
Obtaining a measurement result of illuminance around the display device;
Based on the illuminance, a range that does not lose its change by converting a gradation value of the color gradation of the input image based on a predetermined relationship is set as the first range, and the input Setting a range other than the first range of the color gradation of the image as a second range that loses its change by converting the gradation value into a predetermined gradation value;
Controlling the luminance of the display device so as to have a luminance according to the illuminance,
In the setting step, when the illuminance is brighter than a predetermined reference illuminance, the first range is gradually changed to a brighter side than the predetermined reference range, and the illuminance is higher than the reference illuminance. If the first range is also dark, the first range is gradually changed to the dark side of the reference range,
In the step of controlling the luminance, when the illuminance is brighter than the reference illuminance, the luminance of the display device is set higher than a predetermined reference luminance, and when the illuminance is darker than the reference illuminance, the display A display control method, wherein the brightness of the device is lower than the reference brightness. A program for causing a computer to execute processing for displaying an image based on an input image on a display device whose color gradation and luminance are independent control targets,
Obtaining a measurement result of illuminance around the display device;
Based on the illuminance, a range that does not lose its change by converting a gradation value of the color gradation of the input image based on a predetermined relationship is set as the first range, and the input Setting a range other than the first range of the color gradation of the image as a second range that loses its change by converting the gradation value into a predetermined gradation value;
Causing the computer to execute a step of controlling the luminance of the display device so that the luminance is in accordance with the illuminance,
In the setting step, when the illuminance is brighter than a predetermined reference illuminance, the first range is gradually changed to a brighter side than the predetermined reference range, and the illuminance is higher than the reference illuminance. If the first range is also dark, the first range is gradually changed to the dark side of the reference range,
In the step of controlling the luminance, when the illuminance is brighter than the reference illuminance, the luminance of the display device is set higher than a predetermined reference luminance, and when the illuminance is darker than the reference illuminance, the display A display control program for lowering the brightness of a device below the reference brightness.

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