JP2013009123A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem in which, in high-resolution processing using multiple exposure, it is difficult to detect an edge portion due to a change in a pixel value of a lower end edge portion depending on a phase of a high-resolution image when the high-resolution image is converted into a low-resolution image, and when a pixel value near the lower end edge portion is decimated excessively, image quality of resolution enhancing processing is affected.SOLUTION: Binarization processing is performed on a resolution-enhanced image to detect a lower end edge portion, and a decimation pattern in processing for suppressing fixing explosion is selected based on a pixel value of the lower end edge portion.

Description

  The present invention relates to a technique for suppressing the amount of applied toner for suppressing fixing explosion for multiple exposure processing data to an electrophotographic engine.

  2. Description of the Related Art Conventionally, in an image forming apparatus using electrophotography, a phenomenon called fixing explosion that occurs at the lower end of a line drawing portion perpendicular to the paper conveyance direction is known. This phenomenon occurs when the toner image transferred onto the paper medium is subjected to pressure in the vertical direction of the fixing device and before the fixing process is completed, the moisture contained in the paper is vaporized by the heat of the fixing device, causing air-like It is thought to be caused by being destroyed by pressure.

  In order to solve this problem, a technique is known in which the amount of toner image collapse is reduced by reducing the amount of toner at the lower end of a line drawing, thereby reducing the phenomenon (see, for example, Patent Document 1).

  Patent Document 1 discloses a technique for detecting the edge of the lower end portion of the line drawing perpendicular to the paper conveyance direction and generating image data in which the pixel value at the upper portion of the edge portion is reduced.

  On the other hand, in an electrophotographic image forming apparatus, by irradiating multiple laser beams onto the drum surface to create a latent image peak between the laser scanning lines, the resolution expressed by the actual scanning interval of the laser is exceeded. There is a technique for writing an image with high resolution (Patent Document 2). In Patent Document 2, the intensity of the laser light at the resolution of the image forming apparatus is determined according to the content of the original high-resolution image, and a plurality of pixels are overlapped to form an image between the laser scanning lines. Discloses a technique that can reproduce an original high-resolution image even when laser light is irradiated according to a scanning line having a resolution lower than that of the high-resolution image.

JP 2009-152766 JP Japanese Patent No. 3275050

  Even when the high resolution processing by the multiple irradiation of the laser is performed, the phenomenon of fixing explosion itself is not lost, and it is necessary to perform the fixing explosion suppression processing and the high resolution processing by multiple irradiation at the same time.

  The image obtained by the high resolution processing as in Patent Document 2 is a multi-value image. In Patent Document 1, the average density of a predetermined area in a multivalued image is used as a binarization threshold value for discrimination of the lower edge, but the pixel value of the lower edge of the multivalued image obtained by the technique as in Patent Document 1 is used. Since there is a meaning to achieve higher resolution, it is not always appropriate to binarize with the threshold value obtained by averaging, and if the pixel value at the lower end is reduced too much, high resolution There is a problem that the processing becomes impossible.

Image forming means (102) for writing an image on a paper medium at a predetermined resolution;
Image generation means (301, 303, 304) for generating binary image data having a resolution higher than the predetermined resolution;
Resolution conversion means (304) for converting the image data generated by the image generation means into multi-value image data having the predetermined resolution;
For the image data whose resolution has been converted by the resolution conversion means, it has a thinning processing means (305) for reducing the image data near the lower edge of the line drawing,
The resolution conversion means (304) performs thinning processing on multi-valued image data obtained by multiplying a high-resolution image by a predetermined filter coefficient in accordance with the predetermined resolution (S405, S405),
The thinning processing means (305)
The multi-value image data generated by the resolution conversion means is binarized (S702),
In addition to detecting the line drawing part from the binarized image (S703),
According to the detected pixel value of the lower edge part of the line drawing part, select an image data pattern to be reduced from the vicinity of the lower edge part of the line drawing (S705),
An image forming apparatus (100) characterized in that the image data is reduced from the vicinity of the lower edge of the line drawing (S706).

  When performing high-resolution processing that uses multiple laser exposure, reduction of fixing explosion can be achieved by selecting an appropriate thinning pattern according to the phase of the 1200 dpi image. High resolution can be achieved at the same time.

1 is a block diagram illustrating a configuration of an image forming apparatus. It is sectional drawing of a printer part. It is a block diagram which shows the image processing flow of a controller. It is a figure which shows an example of the process flowchart of a resolution conversion part. It is a figure which shows an example of the processing result of a resolution conversion part. It is a figure which shows an example of the filter coefficient used by the process of a resolution conversion part. It is a figure which shows an example of the process flowchart of a thinning-out process part. It is a figure which shows the example of the process result of the line drawing detection process in the process of a thinning-out process part. It is a figure which shows an example of the thinning pattern used by the process of a thinning process part. It is a figure which shows an example of the process result of a thinning process part. It is a figure which shows another example of the process flowchart of a thinning-out process part. It is a figure which shows the process result by another process example of a thinning-out process part.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

[Example 1]
FIG. 1 shows a schematic block diagram of an image forming apparatus 100 according to an embodiment of the present invention.

  The image forming apparatus 100 according to the present embodiment includes a CPU 101 that controls each unit of the image forming apparatus according to a program stored in a ROM 102, a RAM 103, a ROM 102, and a RAM 103 for storing programs and data for performing various controls and image processing. And an operation unit 103 that allows the user to make various settings and display the settings, and a network I / F 106 for receiving print data from the network. The printer unit 104 further forms an image on recording paper by converting the received print data into image data. The image forming apparatus 100 is connected via a network 111 to a personal computer (PC) 110 that instructs the image forming apparatus 100 to execute printing and transmits data.

  In this embodiment, the printer unit 104 included in the image forming apparatus 100 is an electrophotographic monochrome image forming apparatus. The operation of the printer unit 104 will be described with reference to a cross-sectional view shown in FIG.

  The printer unit 104 drives exposure light with an exposure time corresponding to image data generated by image processing performed by the CPU 101 to form an electrostatic latent image, and develops the electrostatic latent image to form a toner image. Then, after the toner image is transferred to the recording medium 201, the toner image on the recording medium is fixed. The charging unit includes a charger 203 for charging the photoconductor 202. Each injection charger is provided with a sleeve 203S.

  The photosensitive member 202 is configured by applying an organic optical transmission layer to the outer periphery of an aluminum cylinder, and can be rotated by a driving force transmitted from a driving motor (not shown). The drive motor can rotate the photosensitive member 202 in the counterclockwise direction according to the image forming operation.

  The exposure unit is configured to form an electrostatic latent image by irradiating the photosensitive member 202 with exposure light from the scanner unit 204 and selectively exposing the surface of the photosensitive member.

  The developing unit includes a developing unit 206 for visualizing the electrostatic latent image. Each developing device is provided with a sleeve 206S.

  The transfer unit rotates the intermediate transfer member 208 clockwise in order to transfer the toner image from the photosensitive member 202 to the intermediate transfer member 208. Then, the toner image is transferred in accordance with the rotation of the primary transfer roller 207 positioned opposite the photoconductor 202.

  By applying an appropriate bias voltage to the primary transfer roller 207 and making a difference between the rotation speed of the photosensitive member 202 and the rotation speed of the intermediate transfer member 208, the single color toner image is efficiently transferred onto the intermediate transfer member 208 (this). Is called primary transfer.)

  Further, the transfer unit transfers the toner image onto the intermediate transfer member 208 and conveys the toner image to the secondary transfer roller 209 as the intermediate transfer member 208 rotates. Further, the recording medium 201 is conveyed from the paper feed tray 200 to the secondary transfer roller 209, and the toner image on the intermediate transfer member 208 is transferred to the recording medium 201. An appropriate bias voltage is applied to the secondary transfer roller 209 to electrostatically transfer the toner image (this is referred to as secondary transfer). The secondary transfer roller 209 contacts the recording medium 201 at a position 209a while transferring the toner image onto the recording medium 201, and is separated to a position 209b after the processing.

  The fixing unit includes a fixing roller 212 that heats the recording medium 201 and a pressure roller 213 that presses the recording medium 201 against the fixing roller 212 in order to melt and fix the toner image transferred to the recording medium 201 to the recording medium 201. It has. The fixing roller 212 and the pressure roller 213 are formed in a hollow shape, and heaters 214 and 215 are incorporated therein, respectively. The fixing device 211 conveys the recording medium 201 holding the toner image by the fixing roller 212 or the pressure roller 213 and applies heat and pressure to fix the toner on the recording medium 201.

  The recording medium 201 after toner fixing is then discharged to a discharge tray (not shown) by a discharge roller (not shown), and the image forming operation is completed.

  The cleaning unit 210 cleans the toner remaining on the intermediate transfer member 208, and the waste toner remaining after transferring the toner image formed on the intermediate transfer member 208 to the recording medium 201 is stored in a cleaner container. It is done.

  Next, each unit of image processing performed by the CPU 101 reading and executing a program stored in the RAM 103 will be described with reference to FIG.

  First, the image generation unit 301 generates bitmap image data that can be printed from the print data transmitted from the PC 110 described above. Here, the print data is generally a printer description language called PDL (Page Description Language) for creating page image data, and usually includes drawing commands for data such as characters, graphics, and images. . Such print data is analyzed and rasterized to generate multi-value (for example, 8-bit) bitmap image data having a predetermined resolution. The gamma correction unit 302 has desired density characteristics when the image data screen-processed by the screen processing unit 303 described later is transferred to the recording paper with respect to the image data generated by the image generation unit 301. The input image data is corrected using a one-dimensional lookup table. Since the density characteristic changes according to the number of lines, angle, shape, etc. of the screen possessed by the screen processing unit 303 described later, the lookup table used for correction needs to be held in association with the screen.

  Next, the screen processing unit 303 performs screen processing for converting into 1-bit image data that can be printed by the printer unit 104. The screen processing unit 303 holds a threshold matrix according to the resolution information 600 dpi / 1200 dpi and the screen type (number of screen lines and angles) set by the user at the time of print designation on the PC 110, and sets an appropriate threshold matrix according to the setting. Screen processing.

  The screen processing is processing for converting input image data into 1-bit image data that can be printed by the printer unit 102 using a threshold matrix. The threshold matrix is a matrix in which M × N thresholds having a width M and a height N are arranged. In the screen processing, a threshold value corresponding to each pixel of the image data is read from the threshold value matrix, and the pixel value is compared with the threshold value. If the pixel value is equal to or greater than the threshold value, 1 is output, otherwise 0 is output. Thus, the image data is converted into 1 bit. The threshold matrix is repeatedly applied in a tiled manner with a period of M pixels in the horizontal direction and N pixels in the vertical direction.

  In the present embodiment, the screen processing is not limited to this, and any method that binarizes image data with a certain period may be used.

  As described above, the screen processing unit 303 generates 600 dpi 1 bit to 1200 dpi 1 bit image data, and sends the image data to the subsequent resolution conversion unit 304.

  Next, the resolution conversion unit 304 outputs 600 dpi 1-bit image data as it is, while converting 1200 dpi 1-bit image data to 600 dpi multi-value image data. In the present embodiment, it is assumed that the number of bits of multilevel data output by the resolution conversion unit 304 is 4 bits. Detailed processing in this block will be described in detail later using a flowchart.

  The thinning processing unit 305 detects the lower end edge of the line drawing unit for the 600 dpi 1 bit to 600 dpi 4 bit image data generated by the resolution conversion unit 304 and suppresses the explosion by 1 to 4 lines above the detected lower end edge. The process of thinning out the pixels of the part with the pattern is performed. The processing of the thinning processing unit will also be described in detail later using a flowchart.

  Next, the resolution conversion unit 304 realized by the CPU 101 executing the control program stored in the RAM 102 will use the flowchart of FIG. 4 for the resolution conversion processing performed using the image data generated by the screen processing unit 303 as an input. Will be described in detail. Here, an image input to the resolution conversion unit 304 is expressed as I (xs, ys).

  First, in step S401, the resolution conversion unit 304 inspects image resolution information set by the user on the PC 110 and transmitted to the image forming apparatus 100. If the resolution is 600 dpi, a 600 dpi 1-bit image is output as it is (S410), and the process is terminated. If the resolution is 1200 dpi, the process proceeds to S402.

  Next, in S402, the resolution conversion unit 304 secures a memory for 600 dpi 4-bit image data after resolution conversion. This memory area is expressed as O, and the coordinate system at 600 dpi is expressed as (x, y). For all the coordinate systems (x, y) expressed in this way (S403), the processing of S404 to S407 is performed.

Next, in S404, the resolution conversion unit 304 sets the numerical value obtained by doubling the coordinates (x, y) at 600 dpi as the coordinate system (xs, ys) of the 1200 dpi image that is the input image, and in S405, inputs 1200 dpi. Acquire image I (xs, ys) and surrounding 8 pixels. That is,
I (xs-1, ys-1)
I (xs, ys-1)
I (xs + 1, ys-1)
I (xs-1, ys)
I (xs, ys)
I (xs + 1, ys)
I (xs-1, ys + 1)
I (xs, ys + 1)
I (xs + 1, ys + 1)
To get.

  Next, in step S406, the resolution conversion unit 304 performs weighted addition on these nine pixels using filter coefficients. One example of filter coefficients used in this filter processing is shown in FIG. The filter coefficient 1 (600) has 4 in the center, and the surrounding 8 pixels have a weighting coefficient that decreases according to the distance from the center. Although this filter coefficient can be changed according to the state of the printer unit 102, in the present embodiment, it is assumed that the filter coefficient has a numerical value as indicated by the filter coefficient 1. These nine coefficient values are multiplied by the pixel values of nine pixels acquired in S405 and then added. That is, the pixel value of O (x, y) when the filter coefficient 1 is used is calculated as follows.

O (x, y) = f11 * I (xs-1, ys-1) +
f12 * I (xs, ys-1) +
f13 * I (xs + 1, ys-1) +
f21 * I (xs-1, ys) +
f22 * I (xs, ys) +
f23 * I (xs + 1, ys) +
f31 * I (xs-1, ys + 1) +
f32 * I (xs, ys + 1) +
f33 * I (xs + 1, ys + 1)
The pixel value calculated in this way has a value from 0 to 16 because the original 1200 dpi image is 1 bit, but in order to express O (x, y) with 4 bits (0 to 15), Here, the pixel value 16 is rounded to 15.

  In step S407, the resolution conversion unit 304 outputs the pixel value O (x, y) calculated as described above and ends the process.

  FIG. 5 shows a schematic diagram of the result of processing according to the flowchart shown in FIG. Fig. 5 (a) shows 1200dpi 1bit image data before resolution conversion with 1bit pixel value 0 expressed in white and 1 in black. Fig. 5 (b) shows 600dpi 4bit image data after resolution conversion processing. The pixel value is expressed by the darkness of black.

  In FIG. 5B, reference numeral 501.502 is a line drawing having a width of 6 pixels in 1200 dpi image data, but the phase of the start position of the line drawing is different.

  As a result, the result of resolution conversion processing of the line drawing unit 501 is composed of a line 511 having a pixel value 12, two lines 512 having a pixel value 15, and a line 513 having a pixel value 4 in FIG. Will be. When calculated in the same manner, the result of resolution conversion processing of the line drawing unit 502 is composed of a line 521 having a pixel value 4, two lines 522 having a pixel value 15, and a line 523 having a pixel value 12 in FIG. Will be.

  The printer unit 104 controls the intensity of the laser beam irradiated by the laser 204 onto the drum 202 according to the size of each pixel value. The laser beam diameter is approximately 2 microns, which is 42 microns, which is a scanning line interval of 600 dpi. About twice as large. Therefore, the latent image on the surface of the drum 202 by the irradiated laser light is an image obtained by superimposing the latent images by a plurality of laser lights. For example, when superimposing the line 512 and the line 513 at the lower end of the line drawing part, a latent image is formed by thickening the line 512 by an amount corresponding to the pixel value 4 of the line 513, so that the original 1200 dpi image is formed. It is possible to represent the position of the image.

  Next, processing performed by the thinning processing unit 305 realized by the CPU 101 executing and operating the control program stored in the RAM 102 will be described in detail with reference to the flowchart of FIG. Here, an image that the thinning processing unit 305 receives as a processing result of the resolution conversion unit 304 is expressed as I (x, y).

  First, in S701, the thinning processing unit 305 inspects image resolution information set by the user on the PC 110 and transmitted to the image forming apparatus 100. If the resolution is 600 dpi, the process proceeds to S711. If the resolution is 1200 dpi, the process proceeds to S702.

  In S711, the thinning processing unit 305 detects a line drawing having a width of 3 pixels or more in the y direction, and stores the Y coordinate of the lower end position of the line drawing detected in S712 as Ye and the line width as Yh. Next, the thinning processing unit 305 selects a thinning pattern corresponding to the line width Yh in S713, and performs thinning processing using the pattern selected in S706.

  FIG. 8 shows a schematic diagram of the detection processing performed by the thinning processing unit 305 in S712 and the lower end position Ye and the line width Yh stored.

  In the line drawing detection, it is assumed that the input image I (x, y) 800 is processed in blocks of every 8 pixels in the X direction. In the pixel block 801 divided into strips every 8 pixels, it is checked whether there is a black pixel from above in the Y direction, and the presence of the obtained black pixel block 802 is detected. The lowest Y coordinate of the block obtained by detection is stored as the lower edge Y coordinate Yh, and the height of the block is stored as the line width Yh.

  Since I (x, y) is a 1-bit image, the detection process detects a line with a pixel value of 1 over the entire X direction, and the next occurrence of a line with a pixel value of 0 over the entire X direction The value may be Ye, and the width from the line detection position where the pixel value is 1 to the line detection position where the pixel value is 0 may be Yh.

  When the resolution is 600 dpi, the thinning pattern selected in S713 is determined not only by the line width and the pixel value of the lower edge, but by only the line width as in the case of 1200 dpi described later. Details of the thinning pattern to be selected will be described in detail in the description of 1200 dpi processing.

  When the resolution setting is 1200 dpi, the thinning-out processing unit 305 determines that the input image I (x, y) is a predetermined threshold in S702, and 1 when the I (x, y) is greater than or equal to the threshold. In the following case, a threshold image is processed so as to be 0, and a binary image B (x, y) is generated. Here, the threshold is assumed to be other than zero. That is, binarization is performed so that a pixel value is 1 where an image exists.

  Next, the thinning processing unit 305 performs line drawing detection for I (x, y) in S703, and stores the lower edge Y coordinate Ye and the line width Yh in S704. , y) as line images are detected, and Ye and Yh are stored in S704. However, when the resolution setting is 1200 dpi, the line width of the line drawing portion to be detected is 4 lines or more. This is because a line drawing of 6 lines width at 1200 dpi is converted to 4 lines instead of 3 lines when the resolution is converted to 600 dpi.

  Next, in S705, the thinning processing unit 305 selects a thinning pattern according to the pixel value of the input image I (x, Ye) and the line width in the lower edge portion, and uses the thinning pattern selected in S706. Thinning out.

  Here, the details of the thinning pattern selected in S705 will be described with reference to FIG.

  In this embodiment, it is assumed that thinning processing is performed on a line drawing of 4 to 6 line width at 600 dpi, and a thinning pattern for 4 to 6 lines is set. However, depending on the characteristics of the printer unit 102, more Thinning patterns for a large number of lines may be set, and the gist of the present invention is not to limit the number of lines.

  As already seen in FIG. 5, when the same line drawing is converted into a 600 dpi 4-bit image depending on the drawing position at 1200 dpi coordinates, the pixel value at the lower edge may be different. However, if the filter coefficient used in the resolution conversion unit 304 is determined as the filter coefficient 600, the pixel value of the lower edge portion is 12 to 4. By utilizing this, the thinning pattern selection is selected from the thinning pattern table 900.

The pixel value at the bottom edge is 4,
When the line width Yh is 4 lines, the thinning pattern 901
If the line width Yh is 5 lines, the thinning pattern 903
If the line width Yh is 6 lines, the thinning pattern 905
The pixel value at the bottom edge is 12,
If the line width Yh is 4 lines, the thinning pattern 902
If the line width Yh is 5 lines, the thinning pattern 904
If the line width Yh is 6 lines, the thinning pattern 906
Select.

  When the pixel value of the lower edge portion is 4, the pixel value of the line on one line is 15, which is the pixel value constituting the main line portion in the latent image on the drum 202 surface. Use a pattern that is not thinned out. As a result, while maintaining the edge characteristics of the lower end line portion, the toner amount near the line portion can be reduced and the influence of the fixing explosion can be reduced.

  On the other hand, when the resolution setting is 600 dpi, the pixel value at the lower edge is 1 (1 in 4-bit conversion is 15) in the S713 decimation pattern selection. Select a thinning pattern.

  Next, in step S706, the thinning processing unit 305 replaces the white pixel portion in the selected pattern with the detected line drawing unit and outputs the same as the resolution setting 600 dpi / 1200 dpi common processing. The processing of the part 305 is finished.

  FIG. 10 shows a schematic diagram of an image obtained as a result of performing the processing of the thinning processing unit 305 as described above.

  A line drawing unit 1004 having a width of 6 lines in the input image 1001 generated as 1200 dpi 1-bit image data generated by the screen processing unit 303 from the image generation unit 301 is processed by the resolution conversion unit 304, and a line drawing unit in the 600 dpi 4-bit image 1002 As in 1006, a line drawing of 4 lines having a pixel value 4 at the lower end of the line is obtained. On the other hand, the line drawing unit 1005 is processed by the resolution conversion processing unit 304 and becomes a four-line line drawing having a pixel value of 12 at the lower end of the line, like the line drawing unit 1007 in the 600 dpi 4-bit image 1002. The result of the processing of the thinning processing unit 305 for each line drawing unit 1002 is the line drawing units 1008 and 1009 in the thinning processed image 1003, and the line drawing unit 1008 excessively thins the vicinity of the lower edge portion. It prevents that.

  According to the above explanation, fixing explosion by selecting an appropriate thinning pattern according to the phase of 1200 dpi image when fixing explosion reduction processing is performed on high resolution processing image using multiple exposure of laser The reduction effect and high resolution can be achieved at the same time.

[Example 2]
In the first embodiment, the thinning processing unit 305 performs binarization on the input image so that the pixel value other than 0 is 1, and the thinning pattern is selected in consideration of the pixel value at the lower end of the line. However, in the present embodiment, an example will be described in which the binarization processing performed by the thinning processing unit 305 is obtained according to the filter coefficient used by the resolution conversion unit 304, and the selection of the thinning pattern is simplified.

In this embodiment, an example of a flow of processing performed by the thinning processing unit 305 will be described with reference to FIG.
First, the thinning-out processing unit 305 inspects image resolution information set by the user on the PC 110 and transmitted to the image forming apparatus 100 in S1101. If the resolution is 600 dpi, the process proceeds to S1111. If the resolution is 1200 dpi, the process proceeds to S1102. Since S1111 to S1113 are exactly the same as S711 to S713, description thereof will be omitted.

When the resolution setting is 1200 dpi, the thinning processing unit 305 calculates a binarization threshold value from the filter coefficient used by the resolution conversion unit 304 in S1102. That is, the threshold Th is
Th = ((f11 + f12 + f13) + (f11 + f12 + f13) + (f21 + f22 + f23)) / 2
When the numerical value of the filter coefficient 600 is used, Th = (4 + 4 + 8) / 2 and the threshold value is 8.

  Next, in step S1103, the thinning processing unit 305 performs threshold processing so that the input image I (x, y) is 1 when the input image I (x, y) is equal to or greater than the threshold obtained in S1102, and 0 when the input image is equal to or less than the threshold. A valued image B (x, y) is generated.

  Next, the thinning processing unit 305 performs line drawing detection using B (x, y) as an input image in S1104, and stores Ye and Yh in S1104. In the present embodiment, the line drawing portion detected in S1104 is set to 3 lines or more as in 600 dpi, and S1105 and S1106 are exactly the same as the processing at 600 dpi. The selection of the thinning pattern is determined only by the line width at 600 dpi and 1200 dpi, and the thinning pattern is selected from the thinning patterns 907, 908, and 909 according to the line width Yh.

  Finally, in S1107, the thinning processing unit 305 performs a thinning process on the thinning pattern selected in S1106 and S1113 from the line drawing unit of the input image I (x, y), and ends the process.

  A schematic diagram of a processing result image by the thinning processing unit 305 of this embodiment is shown in FIG. In the final post-thinning image, the bottom edge part with a pixel value of 4 in the line drawing unit 1201 is not considered a black pixel in the binarization process, and the bottom edge part in the line detection process has a pixel value above it. There are 15 lines. In addition, since the bottom edge portion with a pixel value of 12 in the line drawing unit 1202 becomes a black pixel even in the binarization processing, the bottom edge portion starts from a line with a pixel value of 12, and the line above it is thinned out by thinning processing .

  As described above, in this embodiment, it is possible to facilitate the process of selecting a process thinning pattern while suppressing excessive thinning.

100 Image forming apparatus 101 CPU
104 Printer unit 105 Operation unit 110 PC
303 Screen processing unit 304 Resolution conversion unit 305 Thinning processing unit

Claims (3)

Image forming means (102) for writing an image on a paper medium at a predetermined resolution;
Image generation means (301, 303, 304) for generating binary image data having a resolution higher than the predetermined resolution;
Resolution conversion means (304) for converting the image data generated by the image generation means into multi-value image data having the predetermined resolution;
For the image data whose resolution has been converted by the resolution conversion means, it has a thinning processing means (305) for reducing the image data near the lower edge of the line drawing,
The resolution conversion means (304) performs thinning processing on multi-valued image data obtained by multiplying a high-resolution image by a predetermined filter coefficient in accordance with the predetermined resolution (S405, S405),
The thinning processing means (305)
The multi-value image data generated by the resolution conversion means is binarized (S702),
In addition to detecting the line drawing part from the binarized image (S703),
According to the detected pixel value of the lower edge part of the line drawing part, select an image data pattern to be reduced from the vicinity of the lower edge part of the line drawing (S705),
An image forming apparatus (100), which performs a process of reducing image data from the vicinity of a lower edge of a line drawing (S706). In the thinning processing means (305),
The selection of the image data pattern to be reduced from the vicinity of the lower edge of the line drawing part is determined from the pixel value of the lower edge part and the line width of the line drawing (S705).
The image forming apparatus (100) according to claim 1, wherein: Image forming means (102) for writing an image on a paper medium at a predetermined resolution;
Image generation means (301, 303, 304) for generating binary image data having a resolution higher than the predetermined resolution;
Resolution conversion means (304) for converting the image data generated by the image generation means into multi-value image data having the predetermined resolution;
For the image data whose resolution has been converted by the resolution conversion means, it has a thinning processing means (305) for reducing the image data near the lower edge of the line drawing,
The resolution conversion means (304) performs thinning processing on multi-valued image data obtained by multiplying a high-resolution image by a predetermined filter coefficient in accordance with the predetermined resolution (S405, S405),
The thinning processing means (305)
A binarization threshold is determined from the filter coefficient used in the resolution conversion means (S1102)
The multivalued image data generated by the resolution conversion means based on the determined threshold value is binarized (S1103),
The line drawing part is detected from the binarized image (S1104),
According to the detected line width of the line drawing part, select an image data pattern to be reduced from the vicinity of the lower edge part of the line drawing (S1106),
An image forming apparatus (100), which performs a process of reducing image data from the vicinity of a lower edge of a line drawing (S1106).