JP4050382B2 - Multi-value image smoothing apparatus and image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming apparatus that displays or prints a bitmap-represented digital image, and more particularly to a smoothing technique for smoothing outlines of characters and figures.
[0002]
[Prior art]
Since digital images use bitmap representation, zigzag irregularities called jaggy occur on the outlines of characters and figures. Smoothing is a technique that corrects jaggies to finer irregularities so that the outline looks like a smooth line to the human eye.
[0003]
Elements constituting an image can be broadly classified into three types: “characters” such as letters and symbols, “graphics” such as line diagrams and draw pictures, and “natural images” such as photographs and paint paintings. Among these three types of elements, elements that require smoothing are elements having a clear outline such as “character” and “graphics”. On the other hand, since a “natural image” is an element whose image value changes substantially continuously, applying smoothing results in an unnatural image.
[0004]
Characters and graphics can be typically represented by binary image data (data in which one pixel value for one color is represented by a 1-bit word). On the other hand, a natural image needs to be expressed by multi-value image data (data in which one pixel value for one color is expressed by a plurality of bits (for example, 8 bits) word). Under such circumstances, the conventional smoothing technology has been developed exclusively as processing for binary image data, and cannot be used for multi-value image data.
[0005]
[Problems to be solved by the invention]
However, in many cases, characters and graphics are expressed in the form of multivalued image data. In the case of a color image, multivalued image data is more common. A typical example of this type of image is an image in which characters and graphics are overwritten on a natural image. Since smoothing cannot be applied to such a multi-valued image, the jaggy of characters and graphics becomes conspicuous. On the other hand, it is possible to perform smoothing after dropping a multi-valued image into a binary image, but this causes a side effect that a natural image that does not need to be corrected is destroyed.
[0006]
Therefore, an object of the present invention is to enable smoothing of characters and graphics selectively in a multi-valued image without affecting a natural image.
[0007]
[Means for Solving the Problems]
A smoothing apparatus for a multi-valued image according to the first aspect of the present invention includes a binarizing unit that binarizes the multi-valued image, and performs smoothing processing on the binarized image output from the binarizing unit. A smoothing unit that outputs an image signal, a halftoning unit that performs a halftoning process on the multi-valued image and outputs a halftone image signal, and a final image obtained by combining the smoothing image signal and the halftone image signal An output unit for outputting a signal. According to this smoothing device, by appropriately performing binarization in the binarization unit, smoothing objects such as characters and graphics and image elements that are not smoothing objects such as natural images are effectively distinguished. A binary image can be obtained. By performing smoothing processing on the binary image, a smoothed image signal obtained by performing smoothing only on the smoothing target can be obtained. By combining this smoothed image signal and a halftoned image signal obtained by separately halftoning a multi-valued image, natural images are naturally in continuous density, and characters and graphics are free from jaggies. A final image signal that can be reproduced with a clear outline can be obtained.
[0008]
As a binarization threshold value, a value that can substantially distinguish an image element to be smoothed from an image element not to be smoothed should be used. For example, a value near the maximum value of the multi-value image value can be used as the threshold value. Further, the threshold value may be variable according to the state of the target image, the user's preference, and the like.
[0009]
A multi-valued image smoothing device according to a second aspect of the present invention includes a binary image generating unit that generates a binary image in which image elements that are to be smoothed and image elements that are not to be smoothed in the multi-valued image are distinguished from each other; A smoothing unit that performs a smoothing process on the binarized image and outputs a smoothed image signal, a halftoning unit that performs a halftoning process on the multi-valued image and outputs a halftone image signal, the smoothed image signal, and the And an output unit that outputs a final image signal by combining the halftone image signal. According to this smoothing apparatus, by performing smoothing on a binary image in which a smoothing target and a non-smoothing target are distinguished, a smoothing image signal obtained by performing smoothing only on the smoothing target can be obtained. By combining this smoothed image signal with a separately prepared halftoning image signal, a final image signal can be obtained that allows natural images to be reproduced naturally and characters and graphics to be reproduced with clear outlines. Can do.
[0010]
In a preferred embodiment, the binary image as described above is generated based on the attribute data specifying the image element to be smoothed in the multi-valued image. This attribute data also specifies areas that may be corrected by the smoothing process and areas that should not be corrected. Based on this information, smoothing correction is applied to areas that should not be corrected. A smoothing image signal is generated so as not to be applied. Further, based on the image value of the multi-value image, the smoothed image signal is generated so that the image value of the smoothing target is reflected in the image value indicated by the smoothed image signal.
[0011]
The present invention can be implemented by dedicated hardware, a computer, or a combination thereof. Further, the present invention can be implemented in a single device such as a printer, or by a plurality of devices such as a host and a printer connected thereto. When a computer is used, the computer program can be installed or loaded into the computer through various media such as disk storage, semiconductor memory, and communication network.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows the overall configuration of a smoothing apparatus according to an embodiment of the present invention applied to a page printer.
[0013]
For example, the page image memory 1 which is a DRAM stores bitmap image data for at least one page or one band obtained by dividing one page. This bitmap map image data is multi-value image data in which one pixel value for one color is expressed by an 8-bit (1 byte) word. In the case of a color image, the image data is usually configured as a set of planes of three or four color components, but the configuration shown in FIG. 1 is a configuration for processing a plane of one color component. Naturally, if different color component planes are processed serially, only one device shown in FIG. 1 is required, but if processing is performed in parallel, a plurality of devices shown in FIG. 1 are required.
[0014]
Since the pixel value of each color component of the image data in the page image memory 1 is a 1-byte word, it indicates a density within a range of 0 to 255 with a resolution of 256 levels. Since the source data of this image data is usually supplied from a host connected to the page printer, the pixel value of each color component of this image data is determined by what kind of image is created by the host. But in practice,
(1) Pixel value of natural image: 0 to 254
(2) Pixel value of at least one color component of character and graphics: 255
There are many cases that become. The present embodiment is configured as follows so as to perform smoothing of characters and graphics by paying attention to this point.
[0015]
Each pixel value (1 byte word) of the image in the page image memory 1 is read out in the order of raster scan, and is input to the 8-raster image register 2 using, for example, SRAM. The eight raster image register 2 is composed of four raster byte registers 25 to 28 and four raster bit registers 21 to 24. Each of the raster byte registers 25 to 28 can store byte words of pixels for one raster. Each of the raster bit registers 21 to 24 can store a bit word binarized by a binarization circuit 3 to be described later for pixels of one raster. Here, “raster” means a main scanning line when raster scanning a page. For example, in the case of a page having a resolution of 600 dpi and a size A4 (8.27 inches × 11.69 inches), one raster is 8. 27 × 600 = about 4960 pixels.
[0016]
The raster byte registers 25 to 28 and the raster bit registers 21 to 24 function as shift registers or FIFO memories, respectively, and output the oldest written pixel value every time a new pixel value is written. Each pixel value (1 byte word) read from the page image memory 1 is first written into the fourth raster byte register 28 shown at the bottom. Each pixel byte word output from the fourth raster byte register 28 is written to the third raster byte register 27 on the one hand and to the binarization circuit 3 on the other hand, where it is input to the fourth binarization unit. It is binarized by 34 and converted into a 1-bit word. Each pixel byte word output from the third raster byte register 27 is written to the second raster byte register 26 on the one hand, and binary by the third binarization unit 33 in the binarization circuit 3 on the other hand. And converted into a 1-bit word. Each pixel byte word output from the second raster byte register 26 is written to the first raster byte register 25 on the one hand, and binary by the second binarization unit 32 in the binarization circuit 3 on the other hand. And converted into a 1-bit word. Each pixel byte word output from the first raster byte register 25 is binarized by the first binarization unit 31 in the binarization circuit 3 and converted into a 1-bit word.
[0017]
Each pixel value (1 bit word) binarized by the first binarization unit 31 is written into the fourth raster bit register 24. Each pixel bit word output from the fourth raster bit register 24 is written into the third raster bit register 23. Each pixel bit word output from the third raster bit register 23 is written into the second raster bit register 23. Each pixel bit word output from the second raster bit register 22 is written into the first raster bit register 21. In this way, the pixel values for eight consecutive rasters are stored in the eight raster image register 2.
[0018]
As described above, the binarization circuit 3 has four binarization units 31 to 34, binarizes each pixel byte word output from the four raster byte registers 25 to 28, and outputs a 1-bit word. Convert to This binarization uses a predetermined threshold, and a pixel byte word indicating a value equal to or higher than the threshold is converted to a bit word “1”, and a pixel byte word less than the threshold is converted to a bit word “0”.
[0019]
The purpose of this binarization is to extract from the image only the image elements to be smoothed such as characters and graphics from the non-smoothing areas such as natural images. For this purpose, the threshold value of the binarization is such that the pixel value of the character and graphics that are to be smoothed can be converted to “1”, and the pixel value of the area that is not to be smoothed can be converted to “0”. The correct value is chosen. Typically, the highest value “255” of the pixel byte word (or its neighborhood value, such as “250” or “240”) is selected as the binarization threshold. As described above, in many images, the character and graphics to be smoothed have the highest pixel value “255” for at least one color component, and those of natural images that are not to be smoothed are distributed from “0” to “254”. Because it is. However, since there are images that do not fall under this, an appropriate threshold may be selected according to the actual state of the image and the user's preference. For example, in an image in which pixel values of a natural image are distributed in a range of “0” to “200” and pixel values of a smoothing target character and graphics are in a range of “100” to “255”, the character and If the user wants to extract all of the graphics reliably and perform the smoothing process, for example, a threshold value may be selected from the range of about “80” to “150”, while the influence of smoothing on the natural image is reduced. If the user places importance on not giving, for example, a threshold value may be selected from a range of about “150” to “250”. In any case, the image element to be smoothed can be substantially distinguished from other image elements that are not to be smoothed (that is, even if they cannot be completely discriminated, they can be roughly distinguished within a practically acceptable range). A threshold is chosen.
[0020]
This binarization threshold may be set manually by the user, or may be automatically set by the printer driver or printer. As an automatic setting method, for example, when the user designates one or more image elements to be smoothed and areas of image elements that are not to be smoothed on the host application screen, based on the pixel values of the designated image elements. Thus, a method is conceivable in which the printer driver or the printer automatically obtains a threshold that can effectively distinguish the two.
[0021]
Now, the pixel bit words of the fifth to eighth rasters output from the four binarization units 31 to 34 of the binarization circuit 3 shown in FIG. The 9th stage shift registers 51 to 58 are inputted to the fifth to eighth shift registers 55 to 58 respectively. In addition, the pixel bit words of the first to fourth rasters output from the first to fourth raster bit registers 21 to 24 of the 8-raster image register 2 pass through the delay circuit 4 to the 8 × 9 pixel register. 5 to the first to fourth 9-stage shift registers 521 to 54, respectively. The delay circuit 4 includes four delay units 41 to 44, and the binarization circuit 3 performs fifth to eighth operations on the pixel bit words of the first to fourth rasters from the raster bit registers 21 to 24. A delay is applied to the same length received by the pixel values of the raster so that the bit words of the pixels aligned on the image in the sub-scan direction of the raster scan are simultaneously input to the 8 × 9 pixel register 5. Accordingly, the 8 × 9 pixel register 5 stores 72 pixel bit words in the 8 × 9 pixel region on the image. This 8 × 9 pixel area moves one pixel at a time over the image by the raster scan method. Hereinafter, the pixel at the center of the 8 × 9 pixel area, that is, the pixel corresponding to the fifth stage 100 of the fifth shift register 55 of the 8 × 9 pixel register 5 is referred to as a “target pixel”.
[0022]
The smoothing circuit 6 takes in a 72-pixel bit word of the 8 × 9 pixel area in the 8 × 9 pixel register 5 and, based on that, has an image element (with a bit word value “1”) in the 8 × 9 pixel area. ), The drawing laser pulse width for the pixel of interest when the contour line is smoothed is calculated, and a laser drive pulse signal modulated in accordance with the calculation result is generated. Here, the relationship between the pulse width of the drawing laser and the size of the dot of the colorant formed thereby in one pixel region is as shown in FIG. 2, for example. That is, according to a laser pulse having a pulse width corresponding to one pixel full size indicated by reference numeral 201, a full size dot 211 is formed in one pixel region 210. Further, according to the laser pulse slightly shorter than the full pulse width as indicated by reference numeral 202, a slightly smaller dot 212 is formed in one pixel region 210. With a shorter laser pulse 203, more dots 213 are formed. The dot size can be adjusted by changing the laser pulse width in this way.
[0023]
FIG. 3 shows an example in which smoothing is performed using this principle. FIG. 3A shows a binarized image of the 8 × 9 pixel area before smoothing, and FIG. 3B shows an image after smoothing. In the image before smoothing in FIG. 3A, pixels corresponding to the image elements to be smoothed (oblique lines in the example in the figure) are indicated by hatching, but these pixels are on the 8 × 9 pixel register 5. Has a bit word value of “1”. Other pixels are shown in white, but they have a bit word value “0” on the 8 × 9 pixel register 5. The smoothing circuit 6 shown in FIG. 1 reads the binarized image data representing the image of FIG. 3A from the 8 × 9 pixel register 5, and the image after smoothing shown in FIG. 3B. The drawing laser pulse width for the pixel of interest 300 is determined so that can be drawn. As a result, in the example of FIG. 3B, the drawing laser pulse for the pixel of interest 300 is determined to be the pulse 202 shown in FIG. Various specific structures of the smoothing circuit 6 that performs such processing are known.
[0024]
The halftoning circuit 7 in FIG. 1 receives the pixel byte word output from the fifth raster byte data 25 of the 8 raster image register 2, and the halftone processing, that is, the density indicated by the pixel byte word is the same density to the human eye. The process of converting to the presence / absence and size of a dot that feels like As a result of this halftoning process, the halftoning circuit 7 determines the drawing laser pulse width for the pixel of interest, and applies the laser drive pulse for the pixel of interest that has been pulse width modulated according to the determination result to the pixel of interest from the smoothing circuit 6. Is output in synchronism with the output of the laser drive pulse for.
[0025]
The OR circuit 8 logically sums the laser drive pulse signal for the target pixel output from the smoothing circuit 6 and the laser drive pulse signal for the target pixel output from the halftoning circuit 7, and draws a laser driver (not shown). ) To generate a drawing laser pulse.
[0026]
With the above configuration, smoothing is selectively performed only on the image elements in the page image that have the bit value “1” in the binarization process, that is, mainly characters and graphics. Of course, if the character or graphic is a primary color (a color consisting of only one color component with a density of 255) or a color consisting of two or three color components with a density of 255, it is an intermediate color including a color component with a density of less than 255. In some cases, if the density of at least one color component is 255, a smoothing effect can be obtained.
[0027]
FIG. 4 shows how the slant straight line of the intermediate color is smoothed in this embodiment. 4A shows before smoothing, and FIG. 4B shows after smoothing.
[0028]
The diagonal line 401 before smoothing in FIG. 4A is, for example, a full pixel size magenta dot 402 corresponding to a density of 100% (value 255) and a quarter pixel size corresponding to a density of 25% (value 64). It is drawn from a yellow dot 403. If this is passed through the above embodiment, the smoothing process is not applied to the yellow dot 403 having a value of 64, but the magenta dot 402 having a value of 255 is subjected to the smoothing process, and printing is performed as indicated by the slanted line 404 in FIG. The Therefore, although the smoothing process is not applied to the yellow dot 403 having a value of 64, the smoothing effect appears as a whole.
[0029]
FIG. 5 shows a second embodiment of the present invention. The same components as those in the first embodiment shown in FIG.
[0030]
The smoothing device according to the second embodiment includes a page attribute memory 9 which is, for example, a DRAM in addition to the device configuration of the first embodiment. The page attribute memory 9 stores attribute data indicating attributes for each pixel of the image stored in the page image memory 1. That is, the page image is composed of attribute planes stored in the page attribute memory 9 in addition to the color component planes of one color, three colors, or four colors stored in the page image memory 1. In this embodiment, the “attribute” of each pixel is whether the pixel is an image element to be smoothed and whether or not a drawing laser pulse for smoothing correction may be issued on the pixel. (Of course, other attributes may be added, or only one point indicating whether smoothing is to be performed). The attribute data is 2 bits per pixel,
(1) 1st bit: “1” = Smoothing target, “0” = No
(2) Second bit: “1” = correction pulse may be output, “0” = no
Means. For example, as shown in FIG. 6, if the attribute data of each pixel included in the area 501 indicated by fine hatching is “11”, this area 501 is an area to be smoothed and may be a smoothing correction pulse. It means that there is. Further, if the attribute data of each pixel included in the areas 502, 503, 504, and 505 indicated by rough hatching on both sides of the smoothing target 501 is “01”, these areas 502, 503, 504, and 505 are displayed. This means that a corrected drawing laser pulse as a result of smoothing the smoothing target 501 may be output. Further, if the pixel attribute data included in the white areas 506 and 507 on the outer side is “00”, the areas 506 and 507 are not subject to smoothing and no correction pulse should be output. means. Based on the attribute data as illustrated in FIG. 6, smoothing as illustrated in FIG. 3 can be performed.
[0031]
Such attribute data may be automatically generated by a host or a printer, or may be created by a user on a host application. For example, in image source data created by an application or print data sent from a host to a printer, characters are character character codes, graphics are vector data or function calls, natural images are bitmap data, and so on. If different image elements are represented in different types of data, the host application, printer driver, or printer imaging process can automatically identify characters, graphics, and natural images based on the data format. Attribute data can be created. In addition, when a user creates or edits a document, painting, or photo on the application, the user can specify a smoothing target, or can specify a region where a correction pulse can be output or a region where a correction pulse cannot be output. By specifying it, the user can create attribute data on the application.
[0032]
Referring to FIG. 5 again, in synchronization with the reading of the byte word of each pixel from the page image memory 1, the attribute data (2-bit word) of the corresponding pixel is read from the page attribute memory 9, for example, It is written in the 4-raster attribute register 10 using SRAM. The 4-raster attribute register 10 is composed of four raster attribute registers 101-104 each capable of storing attribute data for one raster. Each of the four raster attribute registers 101 to 104 operates as a shift register or a FIFO memory. When new pixel attribute data is written, the oldest written pixel attribute data is output.
[0033]
The attribute data (2-bit word) of each pixel read from the page attribute memory 9 is first written in the fourth raster attribute register 104 shown at the bottom. Each pixel attribute data output from the fourth raster attribute register 104 is written to the third raster attribute register 103 on the one hand, and is input to the fourth delay unit 114 in the delay circuit 11 on the other hand. Each pixel attribute data output from the third raster attribute register 103 is written to the second raster attribute register 102 on the one hand, and input to the third delay unit 113 in the delay circuit 11 on the other hand. Each pixel attribute data output from the second raster attribute register 102 is written to the first raster attribute register 101 on the one hand, and is input to the second delay unit 112 in the delay circuit 11 on the other hand. Each pixel attribute data output from the first raster attribute register 101 is input to the first delay unit 111 in the delay circuit 11.
[0034]
As described above, the delay circuit 11 has the four delay units 111 to 114, and binarizes the pixel attribute data output from the four raster attribute registers 101 to 104 by the binarization circuit 3, respectively. Delay by the processing time. Of the four raster attribute data output from the four delay units 111 to 114, the first bit is used as a control signal to a selector interposed between the binarization circuit 3 and the 8 × 9 pixel register 5. Added.
[0035]
The selector 12 includes four selector units 121 to 124, which select four raster pixel bit words and “0” value bit words output from the binarization circuit 3, respectively. In response to the signal of the first bit of the pixel attribute data received as the target signal and added from the delay units 111 to 114 described above, if the signal value of the first bit is “1”, the pixel bit word is If the signal value of the first bit is “0”, a “0” value bid word is selected and output to the 8 × 9 pixel register 5. The bit word output from the first selector unit 121 is also written to the fourth raster bit register 24 in the 8-raster image register 2.
[0036]
The delay circuit 4 generates a delay corresponding to the processing time in the binarization circuit 3 in the first embodiment shown in FIG. 1, but the processing in the binarization circuit 3 in the second embodiment. A delay corresponding to the sum of the time and the processing time in the selector 12 is generated, so that 8 raster pixels lined up in the sub-scanning direction are simultaneously written in the 8 × 9 pixel register 5.
[0037]
With the above configuration, a binarized pixel value is written in the 8 × 9 pixel register 5 only for a pixel to be smoothed whose first bit of attribute data is “1”. A “0” value is written uniformly.
[0038]
By the way, in the first embodiment shown in FIG. 1, the binarization circuit 3 distinguishes between the smoothing target and the non-smoothing target, whereas in this second embodiment, the selector 12 performs this function. The role of the binary circuit 3 is different from that of the first embodiment. That is, the binarization circuit 3 plays a role of limiting the object to be actually smoothed by the pixel value from the smoothing objects specified by the attribute data. For example, if all characters and all graphics are designated as smoothing targets by the attribute data, if “200” is set as a threshold value in the binarization circuit 3, for example, all characters and all graphics The actual smoothing process is performed only for graphics having a pixel value of “200” or more. This smoothing target limiting function is used to exclude a specific image element having a relatively small pixel value from the smoothing target specified by the attribute data, or when creating attribute data, for example, a black character on a white background. This can be used when a specific area in which text is written is designated as a smoothing target, and when printing, it is desired to perform smoothing only on black text in the area. On the other hand, when the smoothing process may be actually performed on all the smoothing targets specified by the attribute data, the threshold value “0” is set in the binarizing circuit 3 or the binarizing circuit 3 and the selector 12 are set. The first bit of the pixel attribute data from the delay circuit 11 may be directly written into the 8 × 9 pixel register 5.
[0039]
As described with reference to the first embodiment, the smoothing circuit 6 generates a corrected laser drive pulse signal after smoothing for the pixel of interest based on the data of 72 pixels in the 8 × 9 pixel register 5. The laser drive pulse output from the smoothing circuit 6 is input to the pulse adjustment circuit 14. The pulse adjustment circuit 14 inputs the pixel byte word output from the fifth raster register 25 of the 8-raster image register 2 through the delay circuit 13 and, based on the value of the pixel byte word, the laser drive pulse from the smoothing circuit 6. The pulse width is adjusted. That is, the pulse width of the laser drive pulse output from the smoothing circuit 6 is the pulse width when the pixel value to be smoothed is “255”, and the pulse width is output from the fifth raster register 25. The width is adjusted to match the actual pixel value to be smoothed. Here, the delay circuit 13 adjusts the timing so that the pixel byte word of the pixel of interest is always input to the pulse adjustment circuit 14. Since pulse width adjustment by the pulse width adjustment circuit 14 may reduce the effect of smoothing, the pulse width adjustment circuit 14 may be removed. Further, means for removing the pulse width adjusting circuit 14 and reflecting the actual pixel value to be smoothed on the image after smoothing may be provided by a different method.
[0040]
The laser drive pulse output from the pulse width adjustment circuit 14 is then input to the gate 15. The gate 15 receives the second bit of the pixel attribute data output from the first delay unit 11 of the delay circuit 11 through the delay circuit 16 and only when the value of the second bit is “1”. The drive pulse is passed and output to the OR circuit 8. Here, the delay circuit 16 adjusts the timing so that the second bit of attribute data of the pixel of interest always enters the gate 15. Due to the action of the gate 15, the correction pulse for the pixel of interest from the pulse adjustment circuit 14 enters the OR circuit 8 only when the pixel of interest is a region where the correction pulse can be output.
[0041]
The laser driving pulse of the pixel of interest after halftoning generated by the halftoning circuit 7 is input to the OR circuit 8 through the delay circuit 17 in synchronism with the laser driving pulse of the pixel of interest from the gate 15. . Then, the laser drive pulse logically ORed by the OR circuit 8 is sent to the drawing laser driver.
[0042]
FIG. 7 shows an example of the result of the smoothing process of the second embodiment.
[0043]
This example is an image in which an oblique straight line runs on a background of 50% density, and a case where this is printed without performing a smoothing process is shown in FIG. FIG. 6B shows attribute data. The area indicated by fine hatching is a slanted line to be smoothed, and the areas indicated by rough hatching on both sides are areas where a correction pulse may be output. FIG. 6C shows an example of printing after performing the smoothing process using this attribute data, and the diagonal lines are smoothed.
[0044]
As mentioned above, although one Embodiment of this invention was described, these embodiment is an illustration for description of this invention to the last, and is not the meaning which limits this invention only to these Embodiment. Therefore, the present invention can be implemented in various forms other than the above-described embodiment. The present invention is applicable not only to laser page printers but also to other types of printers such as inkjet printers and display devices that display images on a screen. In the above-described embodiment, all processing is performed by hardware, but at least a part of the processing can also be performed by computer software.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of a first embodiment of the present invention.
FIG. 2 is a diagram showing a relationship between a pulse width of a laser driving pulse and a dot size.
FIG. 3 is a diagram illustrating an example of smoothing results.
FIG. 4 shows an example of a smoothing result for intermediate colors.
FIG. 5 is a block diagram showing a configuration of a second exemplary embodiment of the present invention.
FIG. 6 is a diagram showing an example of attribute data.
FIG. 7 is a diagram showing an example of smoothing results.
[Explanation of symbols]
1 page image memory
2 8 raster image memory
3 Binarization circuit
5 8 × 9 pixel register
6 Smoothing circuit
7 Halftoning circuit
8 OR circuit
10 4 raster attribute register
12 Selector
14 Pulse adjustment circuit
15 Gate

Claims (7)

A binary image generation unit that generates a binarized image in which an image element that is a smoothing target and an image element that is not a smoothing target in a multi-valued image are distinguished;
A smoothing unit that performs a smoothing process on the binarized image to generate a smoothed image signal, and adjusts the smoothed image signal based on a pixel value of the multi-valued image ;
A halftoning unit that performs a halftoning process on all the pixels of the multi-valued image and outputs a halftone image signal; and
A multi-valued image smoothing apparatus comprising: an output unit that outputs the final image signal by combining the adjusted smoothed image signal and the halftone image signal. The binary image generating unit, the smoothing apparatus according to claim 1, wherein generating the binary image based on the attribute data to the specified image element is a smoothing target in multi-value image. Based on the attribute data in which the smoothing unit designates an area that may be corrected by the smoothing process in the multi-valued image and an area that should not be corrected, the correction is not performed on the incorrect area. claim 1 Symbol placement smoothing apparatus generates the smoothed image signal. The smoothing device according to claim 2 or 3, wherein the attribute data is included in the multi-valued image. A binary image generation unit that generates a binarized image in which an image element that is a smoothing target and an image element that is not a smoothing target in a multi-valued image are distinguished;
A smoothing unit that performs a smoothing process on the binarized image to generate a smoothed image signal, and adjusts the smoothed image signal based on a pixel value of the multi-valued image ;
A halftoning unit that performs a halftoning process on all the pixels of the multi-valued image and outputs a halftone image signal; and
An output unit that outputs the final image signal by combining the adjusted smoothed image signal and the halftone image signal;
A multi-valued image forming apparatus comprising: an image forming unit that reproduces the multi-valued image based on the final image signal. Generating a binarized image that distinguishes between image elements that are to be smoothed and image elements that are not to be smoothed in the multi-valued image;
Performing a smoothing process on the binarized image and outputting a smoothed image signal;
Adjusting the smoothed image signal based on pixel values of the multi-valued image ;
Performing a halftoning process on all pixels of the multi-valued image and outputting a halftone image signal; and
A method for smoothing a multi-valued image, comprising: combining the adjusted smoothed image signal and the halftone image signal to output a final image signal. Generating a binarized image that distinguishes between image elements that are to be smoothed and image elements that are not to be smoothed in the multi-valued image;
Performing a smoothing process on the binarized image and outputting a smoothed image signal;
Adjusting the smoothed image signal based on pixel values of the multi-valued image;
Performing a halftoning process on all pixels of the multi-valued image and outputting a halftone image signal; and
A computer-readable program storing a program for causing a computer to perform a smoothing method for a multi-valued image having a step of outputting a final image signal by combining the adjusted smoothed image signal and the halftone image signal Recording medium.

Images