JP2012121265A - Image forming apparatus and control method thereof - Google Patents

Abstract

A change in a formed image depending on an environment is more preferably compensated.
In an image forming apparatus that processes image data and forms an image with the image forming means, an input means for inputting image data, an attribute determining means for determining an image attribute of each pixel included in the image data, and An acquisition unit that indicates an operating environment of the image forming unit and acquires environmental information including at least temperature information; and an image forming density variation depending on the operating environment in the image forming unit based on the acquired environmental information. A determination unit that determines whether or not an image correction process for compensation is necessary; and an image correction unit that performs the image correction process on the image data when the determination unit determines that the image correction process is necessary. Attribute correction means for correcting an image attribute of a pixel whose pixel value has been changed by the image correction process to an image attribute of a pixel used for determining the pixel value of the pixel Comprises according to the image attribute of each pixel, and generation means for generating a formed image data used by the image forming means.
[Selection] Figure 1

Description

  The present invention relates to an image processing technique in an image forming apparatus, and more particularly to an image processing technique that compensates for changes in a formed image depending on the environment.

  Depending on the output environment, output conditions, and usage status of the image forming unit (photosensitive drum, laser irradiation unit, etc.) (for example, the number of output sheets) The thickness of the characters sometimes changed. For example, when a copier deteriorated by use is output in an environment where the temperature is high, the thickness of fine lines and characters may be output thicker than usual. In addition, the thickness of fine lines and characters may change depending on the type of paper to be output. In order to cope with such a problem, a technique for thinning thin lines or characters in advance in image processing performed prior to image formation is known. For example, Patent Document 1 proposes a technique for performing a thinning process that lowers the pixel value at the edge of a fine line or character (decreases the density).

JP 2009-070128 A

  However, when the thinning process described above is applied to a character having an image (for example, an image having a graphic attribute) in the background, the density of the edge portion of the character becomes light. As a result, an image that appears to have white spots may be output, or an image in which jaggy or the like is noticeable may be output.

  The present invention has been made in view of the above-described problems, and an object thereof is to provide an image processing technique that more suitably compensates for changes in a formed image depending on the environment.

  In order to solve one or more of the problems described above, the image forming apparatus of the present invention has the following configuration. That is, in an image forming apparatus that processes image data and forms an image with an image forming unit, an input unit that inputs image data, an attribute determination unit that determines an image attribute of each pixel included in the image data, An operating unit that indicates an operating environment of the image forming unit, acquires an environmental information including at least temperature information, and compensates for fluctuations in image forming density depending on the operating environment in the image forming unit based on the acquired environmental information. Determining means for determining whether or not image correction processing is necessary, and when the determination means determines that the image correction processing is necessary, the image correcting means for performing the image correction processing on the image data; Attribute correction means for correcting an image attribute of a pixel whose pixel value has been changed by image correction processing to an image attribute of a pixel used to determine the pixel value of the pixel; In accordance with the image attribute of each pixel, including a generation means for generating a formed image data used by the image forming means.

  ADVANTAGE OF THE INVENTION According to this invention, the image processing technique which compensates the change of the formation image depending on environment more suitably can be provided.

1 is a schematic block diagram of an image forming apparatus. It is a flowchart of an image correction process part. It is a figure explaining an environmental information determination part. It is a detailed view of an environmental information determination unit. It is a figure explaining a thinning process and a fattening process. It is a figure which shows the image correction process UI. It is a figure which shows the detailed setting screen of image correction process UI. It is a detailed flowchart of an image correction process. It is a figure which shows the example of environmental information determination. It is a figure which shows the detailed example of environmental information determination. It is a figure which shows the direction of a thinning / thickening process, and a reference pixel. It is a figure which shows various image attributes typically. It is a figure which shows typically the effect by correction of an image attribute. It is a figure explaining the specific process of a fattening process.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. The following embodiments are merely examples, and are not intended to limit the scope of the present invention.

(First embodiment)
The first embodiment of the image processing apparatus according to the present invention will be described below by taking an image forming apparatus as an example.

<Device configuration>
FIG. 1 is a schematic block diagram of an image forming apparatus 100 according to the first embodiment. In the following description, it is assumed that the image forming apparatus 100 is a digital multi-function peripheral that prints out image data read by the image reading unit 10 or image data received from an external device (not shown) by the image receiving unit 11. In the following description, it is assumed that the image forming apparatus 100 uses four color materials (such as toner and ink) of yellow (Y), magenta (M), cyan (C), and black (K). . However, the present invention can also be applied to a case where a combination of other color materials such as red (R), green (G), and blue (B) color materials is used.

  The image forming apparatus 100 includes an image reading unit 10, an image receiving unit 11, a setting user interface (UI) 17, an image processing unit 12 that performs various image processing, a storage unit 15, a CPU 16, and an image output unit 13. The image reading unit 10 reads an input image. For example, the image reading unit 10 is a functional unit that reads a color image or the like. The image receiving unit 11 receives image data from a server that manages image data or a personal computer (PC) that instructs the image forming apparatus to execute printing via an external communication path 14 such as a LAN or the Internet. Receive.

  The image data read by the image reading unit 10 or the image data input to the image receiving unit 11 is input to the image processing unit 12. The scanner image processing unit 120 performs image processing such as shading correction, image area separation processing, and color conversion on the image data read by the image reading unit 10. Note that the image area separation process is a process of adding attribute information of the pixel to each pixel of the image data.

  FIG. 11 is a diagram schematically showing an object image having various attributes included in the image. Specifically, the object image attributes include a character attribute indicating a character 50, a background attribute indicating a background 51, an image attribute indicating an image 52 such as a natural image, a thin line attribute indicating a thin line 53, and a figure. A graphic attribute indicating the graphic 54 is included.

  On the other hand, when the image data is data expressed in a printer description language (PDL), the printer image processing unit 121 interprets a PDL command group included in the image data and outputs an intermediate code. A raster image processor (RIP) in the printer image processing unit 121 develops the intermediate code into a bitmap image and outputs it to the color processing unit 122. On the other hand, the attribute information for each pixel is expanded from the attribute information included in the PDL command group, and is output to the image correction processing unit 123.

  Next, the color processing unit 122 receives image data from the scanner image processing unit 120 or the printer image processing unit 121, and performs RGB → CMYK color conversion processing and the like. The image correction processing unit 123 performs image correction on the CMYK image. In particular, the image correction processing unit 123 performs image processing (thickening processing or thinning processing described later) for compensating for image formation variation due to the environment of the image output unit 13.

  FIG. 2 is a diagram showing more detailed functional blocks of the image correction processing unit 123. An attribute determination unit 123-1, a density determination unit 123-2, a density correction unit 123-3, and an attribute correction unit 123-4 are included. The attribute determination unit 123-1 determines the image attribute of each pixel of the input image data. This determination is performed using the result of the image area separation process input from the scanner image processing unit 120 or the attribute information input to the printer image processing unit 121. The density determination unit 123-2 determines the density (pixel value) of each pixel of the input image data. The density correction unit 123-3 corrects the density (pixel value) of the pixel of interest using the density (pixel value) of each pixel determined by the density determination unit 123-2. The attribute correcting unit 123-4 corrects the attribute information of the pixel whose density (pixel value) has been corrected by the density correcting unit 123-3. The details of the image correction processing in the image correction processing unit 123 will be described later with reference to FIG.

  The filter processing unit 124 performs processing such as edge enhancement and smoothing on the image data input from the image correction processing unit 123. The applied amount control processing unit 125 controls the applied amount suitable for the recording material (recording medium such as paper) based on the filtered image data input from the filter processing unit 124. The gamma processing unit 126 performs gamma processing on the image data based on the image data input from the applied amount control processing unit 125. The dither processing unit 127 performs dither processing on the image data processed by each processing unit described above. By the processing by the filter processing unit 124 and the dither processing unit 127, formed image data of each color of CMYK used by the image output unit 13 is generated.

  Each processing unit from the filter processing unit 124 to the dither processing unit 127 is configured to process the image data using the attribute information of each pixel included in the image data. For example, the dither processing unit 127 applies a high line number screen (for example, 200 lines or more) so that jaggy is not conspicuous for pixels having character attributes or thin line attributes. On the other hand, a low line number screen (for example, about 130 to 170 lines) is applied to pixels having a background attribute, an image attribute, and a graphic attribute in order to reduce the occurrence of color variation in image processing.

  The storage unit 15 includes various storage media such as a random access memory (RAM) and a read only memory (ROM). For example, the RAM is used as an area for storing data and various types of information, or used as a work area for the CPU 16. On the other hand, the ROM is used as an area for storing various control programs. The CPU 16 determines and controls various processes according to programs stored in the ROM. The image output unit 13 outputs an image (for example, image formation output to a recording medium such as printing paper).

  FIG. 3 is a diagram for explaining processing executed by the information adjustment unit 21. The information adjustment unit 21 determines the necessity and amount of correction of image correction processing (thickening processing or thinning processing) in the image correction processing unit 123 based on environment information in the image forming apparatus 100.

  The environmental information determination unit 211 acquires the recording material information related to the recording material acquired from the recording material information acquisition unit 18, the environmental information acquired from the environment information acquisition unit 19, and the durability information acquired from the durability information acquisition unit 20. . That is, information about the operating environment for image formation that can cause a change in the fixing property of a color material (such as toner or ink) to a recording material (such as paper) is acquired. Then, the environment information determination unit 211 determines whether the fattening process or the thinning process is necessary based on these pieces of information.

  Specifically, the fixability and the like vary depending on the type of recording material (high quality paper or recycled paper). Further, the fixability changes depending on the environment such as temperature and humidity of the image output unit 13. Further, the fixability and the like change due to the deterioration of the image output unit 13 over time. The environment information may be configured to use past history information as well as information at the time of image formation output. By using past history information, excessive control can be suppressed.

  When the environment information determination unit 211 determines that the thickening process or the thinning process is necessary, the correction width is calculated, the process proceeds to the image correction setting storage unit 151, and the correction width value is stored in the storage unit 15. On the other hand, when it is determined that the image correction process is not necessary, the process proceeds to the image correction setting storage unit 151 and is stored in the storage unit 15 with the correction width being “0”.

  The determination method in the environment information determination unit 211 will be described in more detail. First, temperature information is acquired from the environment information acquisition unit 19, and it is determined whether or not it is in a “normal temperature range” that does not require image correction processing. The upper and lower threshold temperatures of the “normal temperature range” are stored in the storage unit 15 in advance. When the acquired temperature is in the “normal temperature range”, the correction width is determined as “0”. On the other hand, if the acquired temperature is either “high temperature range” higher than “normal temperature range” or “low temperature range” lower than “normal temperature range”, it is determined that image correction processing is necessary and Set the correction width. Specifically, when it is determined that the temperature is in the low temperature range, it is determined that it is necessary to thicken the image in advance because fine lines and characters tend to be thin (density tends to decrease). On the other hand, when the temperature is high, it is determined that it is necessary to reduce the thickness beforehand because it tends to become fat (the concentration tends to increase). For example, the correction width is determined to be “+1” when it is determined that it is necessary to thicken in advance, and “−1” when it is determined that it is necessary to reduce the width in advance. However, the correction range may be determined in more detail according to the temperature range.

  FIG. 9A is a diagram exemplarily illustrating a correspondence relationship between the temperature and the correction width. Here, the correction width represents the number of pixels, and if it is positive, it means fattening processing, and if it is negative, it means thinning processing. In the section 901, the pixel is thickened by one pixel, but the density of the pixel changes between 0 and 255 (in the case of 8 bits). In the section 902, the pixel is thicker by two pixels, but the density of the first pixel (more inner peripheral pixel) is set to 255, and the density of the second pixel (more outer peripheral pixel) is 0 to 255 (8 Bit case). Hereinafter, for example, the correction width = + 1.5 (pixel) means that the correction density of the first pixel is “255” and the correction density of the second pixel is “128”.

  FIG. 9B is a diagram exemplarily showing another correspondence relationship between the temperature and the correction width. The correspondence relationship shown in FIG. 9A is different from the upper limit (first threshold temperature) and lower limit (second threshold temperature) of the “normal temperature range”. “Temperature” is set more widely. The correspondence shown in FIG. 9B is used, for example, when it is determined that the number of times of use is small based on the durability information acquired from the durability information acquisition unit 20. That is, generally, as the number of times the image output unit 13 is used increases and the deterioration with age progresses, the fluctuation in image formation density increases. Therefore, the relationship shown in FIG. 9B is used while the number of uses of the image output unit 13 is small, and the relationship shown in FIG. 9A is used when the number of uses exceeds a predetermined number. It is. Similarly, the upper and lower threshold temperatures of the “normal temperature range” described above may be changed according to the humidity and the type of recording material.

  Further, it may be configured to change not only the temperature but also the parameter relating to the correction range. Further, the correspondence relationship between the temperature and the correction width may be selectively used according to the correction strength (automatic setting level UI 176 described later with reference to FIG. 6B) set by the user. FIG. 9C exemplarily shows a correspondence relationship when a setting (level 1) for reducing the correction strength is designated by the user.

  FIG. 4 is a diagram illustrating the determination criterion determination process. The determination criterion determination unit 211-1 acquires the recording material information from the recording material information acquisition unit 18, the humidity information from the environment information acquisition unit 19, and the durability information from the durability information acquisition unit 20, and finally the level information from the setting UI 17. get. Thereby, the correspondence illustrated in FIGS. 9A to 9C is determined. Specifically, a plurality of correspondence relationships may be prepared in advance, and may be selected based on recording material information, humidity information, durability information, level information, and the like.

  Thereafter, the fattening determination unit 211-2 acquires the current temperature information from the environment information acquisition unit 19, and corrects it using the correspondence illustrated in FIG. 9 determined by the determination criterion determination unit 211-1. Determine the width. Thereafter, the correction width information is stored in the image correction setting storage unit 151.

  FIG. 8 means a look-up table for a recording material (paper type X) used for selecting a correspondence relationship. Here, nine correspondence relationships 1A to 3C are prepared. Then, one of A to C is selected based on humidity and durability information, and one of levels 1 to 3 is selected based on level information (UI 176) selected by the user. Of course, the correspondence may be derived by substituting the acquired information (humidity, durability information, level) as a parameter into a predetermined mathematical expression.

<Setting UI>
FIG. 6A and FIG. 6B describe settings performed in the setting UI 17. Here, a method for setting information necessary for correction will be described. The parameters set by the setting UI 17 are stored in the image correction setting storage unit 151.

  FIG. 6A is a diagram exemplarily showing a user interface (UI) for setting parameters relating to image correction processing (thickening processing and thinning processing). Specifically, the setting of the correction method, correction width, and correction density for each image attribute (character, thin line, image, graphic) is accepted. In the UI 171, the correction method is selected from four “fat”, “thin”, “none”, and “automatic”. When “automatic” is selected here, automatic setting is performed by the environment information determination unit 211 described above. When “thickening” or “thinning” is selected, the correction width in the UI 172 is fixedly applied. Note that the correction width is specified between 0 and 3 pixels, for example. The correction density in the UI 173 is set to a value indicating the degree of correction of the density of the pixel of interest with respect to the density of the reference pixel in the image correction process. For example, the correction density is specified between 0 and 100%. When “None” is selected, both the correction width and the correction density are set to “0”.

  FIG. 6B is a diagram exemplarily showing a user interface (UI) for performing detailed setting for each color plate in the fattening process. For each color version of YMCK, setting of necessity of correction and setting of correction direction when performing correction are received from the user. Here, for example, if only black is selected, it is possible to thicken (or thin) only black. As the correction direction designated in the UI 175, the direction of the thickening process or the thinning process is designated from eight directions. This is used, for example, to compensate for a difference in image forming characteristics between the main scanning direction and the sub-scanning direction in the image output unit 13. By appropriately setting the correction direction, the quality of the formed image can be kept high.

<Operation of the device>
FIG. 7 is a detailed flowchart of the image correction process performed by the image correction processing unit 123. Here, a case where the thinning process is performed based on the information determined by the information adjustment unit 21 and the setting UI 17 will be described. Note that the following processing shows processing for a certain pixel (target pixel). Actually, the processing described below is sequentially performed on all the pixels of the image data (or pixels in the designated image region). Executed.

  Step S1231 includes sub-step S1231-1 for determining the attribute of the target pixel and sub-step S1231-2 for determining the attribute of the reference pixel. In step S1231-1, the attribute determination unit 123-1 determines whether or not the attribute of the target pixel matches the attribute to be thinned. As described above, image correction processing is specified for each attribute in the UI shown in FIG. 6A, and the specification is stored in the image correction setting storage unit 151. If it is determined that they match (is the target of the thinning process), the process proceeds to S1231-2, and if it is determined not to be the target, the process for the current pixel of interest ends. In S1231-2, the attribute determination unit 123-1 determines whether or not the attribute of the reference pixel corresponding to the current pixel of interest matches the attribute to be thinned. Here, the reference pixel indicates a region in the direction opposite to the direction of thinning specified in the correction direction setting UI 17 in FIG. 6B.

  FIG. 10A is a diagram exemplarily showing the relationship between the target pixel and the reference pixel in the thinning process. When the direction in which the thinning process is performed is set as in the pattern 1001, three pixels in the region indicated by the pattern 1002 that is reversed from the direction become reference pixels. One central pixel corresponds to the target pixel.

  If it is determined in S1231-2 that they do not match, the process proceeds to step S1232, and if it is determined that they match, the process for the current pixel of interest ends. For example, when it is set that the image of the character attribute is to be thinned, the image correction setting storage unit 151 is set so that the target pixel is the character attribute and the reference pixel is other than the character attribute. That is, when the pixel of interest has a character attribute and the reference pixel has a character attribute other than the character attribute, it is determined that the target is to be thinned. That is, the edge region in contact with the background image among the pixels of the character image is determined as a target pixel for the thinning process.

  Step S1232 includes sub-step S1232-1 for determining the density of the target pixel and sub-step S1232-2 for determining the density of the reference pixel, and determines whether or not the pixel should be subjected to the thinning process. . In S1232-1, the density determination unit 123-2 compares the density of the pixel of interest with the first threshold set in the image correction setting storage unit 151. If the density of the pixel of interest is equal to or higher than the first threshold, S1232 Proceed to -2. If the density of the target pixel is less than the first threshold value, it is determined that the target pixel is not subject to thinning processing, and the process for the current target pixel ends. In S1232-2, the density determination unit 123-2 compares the density of the reference pixel with the second threshold set in the image correction setting storage unit 151. If the density of the reference pixel is equal to or higher than the second threshold, S1233 Proceed to If the density of the reference pixel is less than the second threshold value, it is determined that the reference pixel is not subject to thinning processing, and the processing for the current pixel of interest ends.

  As a desirable mode, the target pixel density determination process (S1232-1) is performed for each color plate, and the first threshold value can be set for each color plate. For example, when only the black color is specified for the modified color plate (UI 174), the first threshold value for black is set to “0”, and the first threshold value other than black is set to “255”. As a result, in the target pixel density determination (S1232-1), if the target pixel is black, it can be determined that the pixel should always be subjected to the thinning process.

  For example, if the first threshold value is set to “150”, it is possible to make a setting for thinning only a pixel having a high density. For example, when the second threshold value is set to “0”, it is possible to perform a thinning process on an arbitrary background density.

In step S1233, the density correction unit 123-3 corrects the density of the target pixel with reference to the reference pixel. For example, a value obtained by multiplying the density of the reference pixel by the setting value of the correction density set in the UI 173 is determined as the density of the target pixel after correction. Of course, various other modes of determining the density of the target pixel after correction can be considered. For example, when the correction density is set to “A” (%) in the UI 173,
(Corrected pixel density after correction) = {(current pixel density of interest) × (100−A)% + (reference pixel density) × (A)%}
As described above, a weighting operation may be used.

  Here, a more detailed operation of the density correction unit 123-3 will be described with reference to FIG. Specifically, a case will be described in which the density of the pixel of interest 500 that is the character attribute is calculated at the boundary (edge region) between the image region 520 having the background attribute and the image region 510 having the character attribute. In the left diagram of FIG. 5A, the reference pixels corresponding to the target pixel 500 are three pixels located in the region 501 (all have a density of “0”). When the correction density is 100%, the density of the pixel of interest 500 is replaced with “0”, which is the density of the reference pixel, according to the above formula. As a result, the thinning process can be realized as shown in the right diagram of FIG.

  If the density around the character is not uniform due to the influence of JPEG compression or the like, the average value of the density of the three reference pixels may be replaced. In this way, even if there is a reference pixel with a strong compression noise, it is possible to perform the thinning process appropriately.

  In step S1234, the attribute correcting unit 123-4 corrects the corrected attribute of the target pixel to the reference pixel attribute. For example, if the target pixel has a character attribute and the reference pixel has a background attribute, the target pixel attribute is modified from the character attribute to the background attribute.

In the case of the fattening process The fattening process will be described with reference to FIG. Note that the following processing shows processing for a certain pixel (target pixel). Actually, the processing described below is sequentially performed on all the pixels of the image data (or pixels in the designated image region). Executed.

  In step S1231, the attribute determination unit 123-1 determines whether or not the attribute of the target pixel matches the attribute to be thickened. If it is determined that they match (is the target of the fattening process), the process proceeds to S1231-2. If it is determined not to be the target, the process for the current pixel of interest ends. In S1231-2, the attribute determination unit 123-1 determines whether or not the attribute of the reference pixel corresponding to the current pixel of interest matches the attribute to be thickened.

  FIG. 10B is a diagram exemplarily showing the relationship between the target pixel and the reference pixel in the fattening process. When the direction in which the fattening process is performed is set as in a pattern 1003, three pixels in the region indicated by the pattern 1004 that is reversed from that are reference pixels. One central pixel corresponds to the target pixel.

  If it is determined in S1231-2 that they do not match, the process proceeds to step S1232, and if it is determined that they match, the process for the current pixel of interest ends. For example, when it is set to thicken a character attribute image, the image correction setting storage unit 151 is set such that the target pixel is other than the character attribute and the reference pixel is the character attribute. In other words, when the target pixel is other than the character attribute and the reference pixel is the character attribute, it is determined that the image correction processing is to be performed. That is, the edge region in contact with the character image among the pixels of the background image is determined as the target pixel for the image correction process.

  Step S1232 includes sub-step S1232-1 for determining the density of the target pixel and sub-step S1232-2 for determining the density of the reference pixel, and determines whether the pixel is to be subjected to image correction processing. In S1232-1, the density determination unit 123-2 compares the density of the pixel of interest with the third threshold set in the image correction setting storage unit 151. If the density of the pixel of interest is equal to or higher than the third threshold, S1232 Proceed to -2. If the density of the target pixel is less than the third threshold value, it is determined that the target pixel is not subject to the image correction process, and the process for the current target pixel ends. In S1232-2, the density determination unit 123-2 compares the density of the reference pixel with the fourth threshold set in the image correction setting storage unit 151. If the density of the reference pixel is equal to or higher than the fourth threshold, S1233 Proceed to If the density of the reference pixel is less than the fourth threshold value, it is determined that the pixel is not subject to image correction processing, and the processing for the current pixel of interest ends.

  Note that the third threshold value and the fourth threshold value are determined by, for example, settings in the UI illustrated in FIG. 6B. As a desirable mode, the reference pixel density determination process (S1232-2) is performed for each color plate, and the fourth threshold value can be set for each color plate. For example, when only the black color is specified for the modified color plate (UI 174), the fourth threshold value for black is set to “0” and the fourth threshold value other than black is set to “255”. As a result, in the reference pixel density determination (S1232-2), if the reference pixel is black, it can be determined that the pixel should always be subjected to image correction processing. Further, for example, when the third threshold is set to “0”, it is possible to perform the fattening process for an arbitrary character density.

  In step S1233, the density correction unit 123-3 corrects the density of the target pixel with reference to the reference pixel. Here, a more detailed operation of the density correcting unit 123-3 will be described with reference to FIG. Specifically, a case where the density of the pixel of interest 500 as the background attribute is calculated at the boundary (edge area) between the image area 520 having the background attribute and the image area 510 having the character attribute will be described. In the left diagram of FIG. 5B, reference pixels corresponding to the target pixel 500 are three pixels located in the region 502. Two of the three reference pixels have a density of “255” and one has a density of “0”. Here, it is replaced with “255” which is the maximum value of the density of the reference pixel. As a result, as shown in the right diagram of FIG. 5B, the fattening process can be realized.

  In step S1234, the attribute correcting unit 123-4 corrects the corrected attribute of the target pixel to the reference pixel attribute. For example, if the target pixel is a background attribute and the reference pixel is a character attribute, the target pixel attribute is modified from the background attribute to the character attribute.

  In the above description, the character attribute pixel density is “255” and the background attribute pixel density is “0”. However, the character attribute pixel density is the background attribute pixel density. The same processing can be applied if the density is higher than the pixel density. If the density of the character attribute pixels is smaller than the density of the background attribute pixels, such as white characters, the character attribute image is thickened in the high temperature range, and the character attribute image is reduced in the low temperature range. It is good to comprise so that a process may be performed.

<Effects of First Embodiment>
FIG. 12 is a diagram schematically illustrating a state of a formed image when image correction processing (thickening processing) is performed.

  An enlarged view of an image 1210 obtained by performing the fattening process on the image 1200 including the image area 520 having the background attribute and the image area 510 having the character attribute is exemplarily shown. The image 1210 includes an image region 530 whose pixel value has been changed by the thickening process.

  In the conventional technique, the attribute corresponding to the image area of the image area 530 is not corrected (that is, the background attribute remains). Therefore, when the image 1210 is processed by the dither processing unit 127, the image area 530 is processed by applying a low-line number screen (for example, about 130 to 170 lines) in order to reduce the occurrence of color variation in the image processing. As a result, in some cases, an image 1210a that appears to have the white spots described in the background art is output.

  On the other hand, in the first embodiment, the attribute corresponding to the image area of the image area 530 is corrected (that is, corrected to the character attribute). Therefore, when the image 1210 is processed by the dither processing unit 127, the image area 530 is processed by applying a high-line number screen (for example, 200 lines or more) so that jaggies caused by the image processing are not noticeable. As a result, it is possible to reduce the output of an image that appears to have white spots.

  Here, the processing in the dither processing unit 127 has been described. However, by correcting the attribute corresponding to the image area of the image area 530 and performing processing based on the attribute, the filter processing unit 124, the applied amount control processing unit 125, the gamma processing unit 126, and the like are more suitable. It can be expected that a processing result will be obtained.

  Furthermore, information such as a point indicating the line width and the number of pixels may be added together with the attribute information output from the raster image processor (RIP) in the printer image processing unit 121. In that case, by specifying the point and the number of pixels to be thickened or thinned for each attribute, for example, the situation where the width of the thin line after thinning processing becomes 0 pixels and disappears can be reduced. It becomes possible.

  As described above, according to the first embodiment, it is possible to compensate for the image forming density depending on the environment, and to reduce image deterioration due to the image correction processing for the compensation.

(Second Embodiment)
In the second embodiment, a case where image correction processing for non-integer pixels (for example, 1.5 pixels) is performed will be described. Since the apparatus configuration and the schematic operation of the apparatus are the same as those in the first embodiment, description thereof will be omitted. Hereinafter, the fattening process for 1.5 pixels will be described with reference to FIG. FIG. 13 is a diagram corresponding to FIG. 5B in the first embodiment.

  FIG. 13 is a diagram schematically illustrating the thickening process for 1.5 pixels. Specifically, as in FIG. 5B, the density of the pixel of interest 500 that is the background attribute is calculated at the boundary (edge region) between the image area 520 having the background attribute and the image area 510 having the character attribute. Is described. However, since the thickening process for 1.5 pixels is performed, density correction occurs even when the pixel of interest is located at a position separated by 2 pixels from the image area 510 having the character attribute. That is, 1.5 pixels are distributed to the pixels separated by 1 pixel, “1.0”, and “0.5” is distributed to the pixels separated by 2 pixels.

  FIG. 13A is a diagram showing a fattening process in a pixel separated by two pixels from the image area 510 having a character attribute. Here, the density of the pixel of interest 1300 is determined using the density of the pixel within the reference pixel area 1301 and having the character attribute. That is, it is determined using a value obtained by multiplying the density of any of the three pixels in the image area 510 in the area 1301 by 0.5 distributed as described above. As a result, the density of the target pixel after correction is set to an average density of the density of the pixel in the image area 520 and the density of the pixel in the image area 510. On the other hand, FIG. 13B is a diagram showing a fattening process in a pixel separated by one pixel from the image area 510 having a character attribute. It is determined using a value obtained by multiplying “1,0” distributed as described above. As a result, the density of the target pixel after correction is set to the same density as the density of the pixel in the image area 510. By performing these processes, a thickening process for 1.5 pixels as shown in FIG. 13C can be realized.

(Other examples)
The present invention can also be realized by executing the following processing. That is, software (program) that realizes the functions of the above-described embodiments is supplied to a system or apparatus via a network or various storage media, and a computer (or CPU, MPU, or the like) of the system or apparatus reads the program. It is a process to be executed.

Claims (5)

An image forming apparatus that processes image data and forms an image with an image forming unit.
Input means for inputting image data;
Attribute determination means for determining an image attribute of each pixel included in the image data;
An acquisition unit that indicates an operating environment of the image forming unit and acquires environmental information including at least temperature information;
A determination unit that determines whether or not an image correction process for compensating for a variation in image formation density depending on an operating environment in the image forming unit is necessary based on the acquired environment information;
An image correcting unit that performs the image correcting process on the image data when the determining unit determines that the image correcting process is necessary;
Attribute correction means for correcting an image attribute of a pixel whose pixel value has been changed by the image correction processing to an image attribute of a pixel used to determine a pixel value of the pixel;
Generating means for generating formation image data used in the image forming means according to an image attribute of each pixel;
An image forming apparatus comprising: Further comprising designation means for designating an image attribute to be subjected to the image correction processing;
The image forming apparatus according to claim 1, wherein the image correcting unit is configured to correct a density of pixels in an edge region of an image region having an image attribute specified by the specifying unit.   The image forming apparatus according to claim 2, wherein the image correction process includes a thinning process for reducing the density of pixels in the edge region and a thickening process for increasing the density of pixels in the edge region.   The determination unit determines that the thinning process is necessary when the temperature information indicates a temperature higher than a first threshold temperature, and the temperature information is lower than a second threshold temperature lower than the first threshold temperature. The image forming apparatus according to claim 3, wherein when the temperature is low, it is determined that the fattening process is necessary. A method of controlling an image forming apparatus that processes image data and forms an image with an image forming unit,
An input step in which the input means inputs image data;
An attribute determining step for determining an image attribute of each pixel included in the image data;
An acquisition step of acquiring an environment information including at least temperature information, wherein the acquisition unit indicates an operating environment of the image forming unit;
A determination step for determining whether or not an image correction process for compensating for fluctuations in image formation density depending on an operating environment in the image forming unit is necessary based on the acquired environment information;
When the image correction means determines that the image correction processing is necessary in the determination step, an image correction step of performing the image correction processing on the image data;
An attribute correcting step for correcting an image attribute of a pixel whose pixel value has been changed by the image correcting process to an image attribute of a pixel used to determine a pixel value of the pixel;
A generating step of generating formation image data used in the image forming unit according to an image attribute of each pixel;
The control method characterized by including.