JP2004015231A - Image processor, image forming apparatus, image processing method, and program for allowing computer to execute the method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image processing method for generating image data of an image with higher image quality without increasing the amount of the image data and degrading the image processing efficiency. <P>SOLUTION: An image processing apparatus 100 for processing half-tone data containing a dot pattern depending on the lightness is provided with a dot pattern control means 104 for correcting the shape of the dot pattern by controlling an ON / OFF timing of the pulse emitted to a photoreceptor. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image processing apparatus, an image forming apparatus, an image processing method for processing halftone data including a dot pattern corresponding to brightness, and a program for causing a computer to execute the method.
[0002]
[Prior art]
In order to obtain a high-quality image in an image output device such as a printer, the tone and hue of the original image must be reproduced in a good state. As a method of reproducing the gradation of an image in a digital system, a halftone technique is known.
[0003]
The halftone technique is a method of expressing a gradation by using binary data. In the halftone technique, for example, an area gradation method such as a dither method (pseudo halftone processing) is used.
[0004]
In the halftone technique using the dither method, image data is divided into halftone cells of a predetermined size. Each halftone cell expresses a gradation by a black pixel region, that is, a dot pattern. The shape of the dot pattern is predetermined according to each gradation.
[0005]
In recent years, in image processing using a halftone technique, a more efficient method and a method of obtaining a higher quality image have been proposed. For example, in Japanese Patent Application Laid-Open No. 2000-255120, image data that has been binarized at a first resolution (low resolution) is subjected to multi-level processing, and image data that has been subjected to multi-level processing is converted to a first resolution A method for converting to a higher second resolution (higher resolution) is disclosed. Japanese Patent Application Laid-Open No. 2000-32266 discloses a method for improving image quality by applying a plurality of different halftone techniques to one image.
[0006]
[Problems to be solved by the invention]
It is desired to provide a higher quality halftone image, and the inventor studied a method of obtaining a higher quality image by using a halftone technique. In order to obtain a higher-quality image by using the halftone technique, the reproducibility of gradation should be improved. This can be achieved by increasing the number of gradations that can be expressed in the halftone cell. However, since the minimum unit of image data is one pixel, if the number of pixels included in one halftone is increased, the number of halftone cells included in the image data decreases. For this reason, the resolution of the image is reduced. Therefore, even if the reproducibility of the gradation is improved, the image quality is not always improved. As described above, in the halftone technique, there is a problem that the reproduction of the gradation is restricted by the number of pixels constituting the image data.
[0007]
The present invention has been made in view of the above, and an image processing method for creating image data of a higher quality image without increasing the data amount of image data and without reducing the efficiency of image processing. The purpose is to get.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, an invention according to claim 1 is an image processing apparatus for processing halftone data including a dot pattern corresponding to brightness, wherein on / off timing of a pulse applied to a photoconductor is provided. And a dot pattern control means for correcting the shape of the dot pattern by controlling the dot pattern.
[0009]
According to the first aspect of the present invention, the dot pattern control unit controls the on / off timing of the pulse applied to the photoconductor so that a unit smaller than a pixel forming the dot pattern is set as a minimum unit. , The shape of the dot pattern can be corrected. As described above, by correcting the dot pattern with a unit smaller than a pixel as a minimum unit, a high-quality image can be reproduced without increasing the data amount and without reducing the processing efficiency.
[0010]
According to a second aspect of the present invention, in the image processing apparatus according to the first aspect, the dot pattern control means corrects the shape of the dot pattern to a shape closer to a rectangle.
[0011]
According to the second aspect of the present invention, the dot pattern control means corrects the shape of the dot pattern to a shape closer to a rectangle. Can be reproduced.
[0012]
According to a third aspect of the present invention, in the image processing apparatus according to the first or second aspect, when the dot pattern control means corrects the shape of the dot pattern, the dot pattern before correcting the shape is used. It is characterized in that the area of the pattern and the area of the dot pattern after correcting the shape are kept substantially constant.
[0013]
According to the third aspect of the present invention, when correcting the shape of the dot pattern, the dot pattern control means determines the area of the dot pattern before correcting the shape and the area of the dot pattern after correcting the shape. Keep almost constant. Therefore, by correcting the shape of the dot pattern, the area of the dot pattern changes, and accordingly, it is possible to avoid a change in the brightness indicated by the dot pattern.
[0014]
According to a fourth aspect of the present invention, in the image processing apparatus according to any one of the first to third aspects, the dot pattern control means outputs a dot pattern image output from an output device based on the dot pattern. The size of the dot pattern is corrected to a size determined based on the brightness of the dot pattern.
[0015]
According to this invention, the dot pattern control means corrects the size of the dot pattern to a size determined based on the brightness of the dot pattern image output from the output device based on the dot pattern. Can be. Therefore, since the size of the dot pattern can be corrected according to the characteristics of each output device, the reproducibility of the original image in the dot pattern image output from the output device can be kept good.
[0016]
According to a fifth aspect of the present invention, in the image processing apparatus according to the fourth aspect, the dot pattern control means includes an ideal brightness of a dot pattern image output from an output device based on the dot pattern; The size of the dot pattern is reduced to a size determined according to a difference between the brightness of the dot pattern image actually output from the output device.
[0017]
According to the fifth aspect of the present invention, the dot pattern control means controls the ideal brightness of the dot pattern image output from the output device based on the dot pattern and the dot pattern image actually output from the output device. The size of the dot pattern is reduced to a size determined according to the difference from the brightness. Therefore, when the brightness of the actual dot pattern image is higher than the ideal brightness of the dot pattern image, by reducing the size of the dot pattern, the brightness of the image increases and the reproducibility of the image decreases. Can be suppressed.
[0018]
According to a sixth aspect of the present invention, there is provided an image forming apparatus for outputting halftone data including a dot pattern corresponding to lightness, wherein on / off timing of a pulse applied to a photosensitive member is controlled. A dot pattern control means for correcting the shape of the dot pattern; and an output means for outputting the halftone data in which the shape of the dot pattern has been corrected.
[0019]
According to this invention, the dot pattern control means controls the ON / OFF timing of the pulse applied to the photoreceptor, so that a unit smaller than a pixel forming the dot pattern is a minimum unit. As a result, the shape of the dot pattern can be corrected. By correcting the dot pattern with a unit smaller than the dot pixel as the minimum unit in this manner, good reproducibility of the image can be maintained, so that a higher quality image can be output.
[0020]
According to a seventh aspect of the present invention, there is provided an image processing method for processing halftone data including a dot pattern corresponding to brightness, wherein the on / off timing of a pulse applied to a photosensitive member is controlled. And a dot pattern control step of correcting the shape of the dot pattern.
[0021]
According to the seventh aspect of the present invention, the dot pattern control means controls the on / off timing of the pulse applied to the photoreceptor so that a unit smaller than a pixel forming a dot pattern is a minimum unit. As a result, the shape of the dot pattern can be corrected. As described above, by correcting the dot pattern with a unit smaller than a pixel as a minimum unit, a high-quality image can be reproduced without increasing the data amount and without reducing the processing efficiency.
[0022]
According to an eighth aspect of the present invention, in the image processing method according to the seventh aspect, the dot pattern control step corrects the shape of the dot pattern to a shape closer to a rectangle.
[0023]
According to the eighth aspect of the present invention, in the dot pattern control step, the shape of the dot pattern is corrected to a shape closer to a rectangle. Can be reproduced.
[0024]
According to a ninth aspect of the present invention, in the image processing method according to the seventh or eighth aspect, in the case where the dot pattern control step corrects the shape of the dot pattern, the dot pattern before the shape correction is performed. It is characterized in that the area of the pattern and the area of the dot pattern after correcting the shape are kept substantially constant.
[0025]
According to the ninth aspect of the present invention, the dot pattern control step includes, when correcting the shape of the dot pattern, the area of the dot pattern before the shape correction and the area of the dot pattern after the shape correction. Keep almost constant. Therefore, by correcting the shape of the dot pattern, the area of the dot pattern changes, and accordingly, it is possible to avoid a change in the brightness indicated by the dot pattern.
[0026]
According to a tenth aspect of the present invention, in the image processing method according to any one of the seventh to ninth aspects, the dot pattern control step includes the step of: outputting a dot pattern output from an output device based on the dot pattern. The size of the dot pattern is corrected to a size determined based on the brightness of the image.
[0027]
According to the tenth aspect, in the dot pattern control step, the size of the dot pattern is corrected to a size determined based on the brightness of the dot pattern image output from the output device based on the dot pattern. Can be. Therefore, since the size of the dot pattern can be corrected according to the characteristics of each output device, the reproducibility of the original image in the dot pattern image output from the output device can be kept good.
[0028]
According to an eleventh aspect of the present invention, in the image processing method according to the tenth aspect, the dot pattern control step includes the step of controlling a dot pattern image output from an output device based on the dot pattern based on an ideal brightness and an actual brightness. The size of the dot pattern is reduced at a ratio determined according to a difference between the brightness of the dot pattern image output from the output device.
[0029]
According to the eleventh aspect of the present invention, the dot pattern control means controls the ideal brightness of the dot pattern image output from the output device based on the dot pattern and the dot pattern image actually output from the output device. The size of the dot pattern is reduced to a size determined according to the difference from the brightness. Therefore, when the brightness of the actual dot pattern image is higher than the ideal brightness of the dot pattern image, by reducing the size of the dot pattern, the brightness of the image increases and the reproducibility of the image decreases. Can be suppressed.
[0030]
According to a twelfth aspect of the present invention, there is provided a program for causing a computer to execute the image processing method according to any one of the seventh to eleventh aspects. Can be performed by
[0031]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, preferred embodiments of an image processing apparatus according to the present invention will be described in detail with reference to the accompanying drawings. The image forming apparatus of the present invention may be a printer. Further, it may be a copying machine. Further, it may be a facsimile, a scanner, or a multifunction peripheral.
[0032]
(Embodiment 1)
Embodiment 1 of the present invention describes a printer as an example of an image forming apparatus. The printer according to the first embodiment acquires image data, converts the acquired image data into halftone data, and outputs the halftone image as a printed matter.
[0033]
FIG. 1 is a schematic block diagram illustrating a functional configuration of the printer 100 according to the embodiment. The printer 100 includes a data acquisition unit 101, a data conversion unit 102, a data conversion table 103, a dot pattern control unit 104, a dot pattern conversion table 105, a pulse control unit 106, and a printing unit 108. .
[0034]
In FIG. 1, the characteristic functional configuration of the printer 100 is schematically shown as a unit. However, in actuality, the functional configuration shown in FIG. 1 is realized by cooperation of various types of hardware configuring the printer 100. For example, the function of the data conversion unit 102 is realized by a program stored or loaded in the ROM or the RAM being executed by the CPU. Further, the printing unit 108 is realized by cooperation of a photoreceptor, an intermediate transfer body, and a developing device (not shown).
[0035]
The data acquisition unit 101 acquires image data from a device connected to the printer 100, such as a personal computer or a digital camera.
[0036]
The data conversion table 103 stores each gradation in association with a dot pattern predetermined for each gradation. The data conversion unit 102 receives image data from the data acquisition unit 101. Then, the image data is converted into halftone data. Specifically, the data conversion unit 102 divides the image data into halftone cells, and determines the gradation of each halftone cell. Further, a halftone dot corresponding to the gradation of the halftone cell in the data conversion table 103 is formed in this halftone cell.
[0037]
The dot pattern conversion table 105 stores each gradation and correction information predetermined for pulse data at each gradation in association with each other. Here, the correction information is information used when correcting the dot pattern.
[0038]
The dot pattern control unit 104 receives the halftone data from the data conversion unit 102. The dot pattern control unit 104 converts halftone data into pulse data. Further, the dot pattern control unit 104 corrects the dot pattern in the pulse data based on the correction information associated with the gradation of the pulse data in the dot pattern conversion table 105. The processing in the dot pattern control unit 104 will be described in detail with reference to FIG.
[0039]
The pulse control unit 106 irradiates a pulse to a photoconductor (not shown). The pulse control unit 106 receives the modulated pulse data from the dot pattern control unit 104, and controls ON / OFF of the pulse based on the received pulse data. The printing unit 108 prints a halftone image based on ON and OFF of the pulse in the pulse control unit 106.
[0040]
Hereinafter, the correction information stored in the dot pattern conversion table 105 will be described. The correction information is data associated with the corrected dot pattern for each dot pattern. That is, when receiving the dot pattern of the predetermined gradation, the dot pattern control unit 104 converts the received dot pattern into a corrected dot pattern associated with the dot pattern in the correction information.
[0041]
FIG. 2 is a diagram for explaining an example of the correction information. The correction information associates, for example, the dot pattern 510 before correction shown in FIG. 2A with the dot pattern 520 after correction shown in FIG. 2B.
[0042]
The dot pattern 510 illustrated in FIG. 2A has three pixels 512, 514, and 516. That is, the dot pattern 510 is formed in a shape lacking the upper right pixel 518 from the rectangle formed by the four pixels 512, 514, 516, and 518. That is, when the dot pattern 510 is divided into an upper part and a lower part, the area of the upper part is smaller by one pixel than the area of the lower part. Therefore, the pixel 516 and the pixel 518 are divided into four grids 516a, 516b, 516c, 516d, and 518a, 518b, 518c, 518d, respectively, and the area to which black is allocated is changed in grid units. That is, white is assigned to the left grids 516b and 516c in the pixel 516, and black is assigned to the right grids 518a and 518d in the pixel 518 instead.
[0043]
As described above, the dot pattern 510 shown in FIG. 2A is formed by three pixels, and cannot be corrected to a rectangle in pixel units. However, when the clock interval of the pulse control unit 106 is smaller than one pixel, the pulse control unit 106 corrects the rectangular dot pattern 520 as shown in FIG. can do.
[0044]
Thus, when the clock interval of the pulse control unit 106 is smaller than one pixel, the position of the dot can be changed relatively freely, and the shape of the dot pattern can be made closer to a rectangle.
[0045]
Note that the corrected dot pattern 520 shown in FIG. 2 is an example of a dot pattern in a case where the pulse control unit 106 generates a pulse at a clock interval corresponding to a grid having an area of 画素 of one pixel.
[0046]
Each of the dot pattern 510 before correction and the dot pattern 520 after correction shown in FIG. 2 have three pixels. Thus, in the correction information, the dot patterns having the same area are associated as the dot patterns before and after the correction. In the halftone technique, since the gradation is expressed by the area of the dot pattern, when the area of the dot pattern changes, the corresponding gradation changes. Thus, by keeping the area of the dot pattern constant as described above, it is possible to reduce a change in gradation.
[0047]
Hereinafter, a method of correcting a dot area using pulse width pulse position modulation will be described. FIG. 3A schematically shows halftone data 200 in which dots 210 and 220 are arranged every other pixel. FIG. 3B shows pulse data 300 created by the dot pattern control unit 104 based on the halftone data 200. In the pulse data 300, ON 302 and OFF 304 of the pulse are switched according to the positions of the dots 210 and 220 of the halftone data 200.
[0048]
The dot pattern control unit 104 can perform pulse width modulation on the pulse data 300 shown in FIG. 3B and convert the pulse data into pulse data 310 shown in FIG. FIG. 4B shows a halftone image 400 printed by the printing unit 108 based on the pulse data 310 shown in FIG. 4A.
[0049]
The pulse widths of the pulses ON312, 314, and 316 included in the pulse data 310 shown in FIG. 4A are {(1/2) t}, t, and {(3/2) t}, respectively. Further, in response to the pulse ON shown in FIG. 4A, the dot area 402 shown in FIG. 4B has a width corresponding to a half pixel. The dot area 404 has a width corresponding to one pixel, and the dot area 406 has a width corresponding to 3/2 pixels.
[0050]
In this manner, the pulse control unit 106 can switch the pulse with the clock interval {(1/2) t} of the pulse as the minimum unit. Therefore, by performing pulse width modulation with a unit smaller than the length of one side of one pixel as the minimum unit, the width of the dot pattern can be more freely corrected.
[0051]
The dot pattern control unit 104 can also perform pulse position modulation on the pulse data 300 shown in FIG. 3B and convert it into pulse data 320 shown in FIG. FIG. 5B shows a halftone image 420 printed by the printing unit 108 based on the pulse data 320 shown in FIG. 5A.
[0052]
The start position 324 of the pulse ON 325 in the pulse data 320 shown in FIG. 5A is different from the pixel boundary position 231 of the halftone data 200 by the length [(1/2) t]. As described above, the dot pattern control unit 104 can change the pulse position using [(1/2) t] as the minimum unit.
[0053]
As described above with reference to FIGS. 4 and 5, by performing so-called pulse width pulse position modulation that modulates at least one of the pulse width and the pulse position on the pulse data, the shape of the dot pattern is changed. Can be corrected.
[0054]
FIG. 6 is a block diagram illustrating a hardware configuration of the printer 100. In the printer 100, a host I / F 3, a CPU 4, a ROM 5, a RAM 6, a line buffer 21, an engine I / F 8, and a printer engine 10 are connected via a system bus 9.
[0055]
The host I / F 3 includes a network and various interfaces, and acquires image data from outside. Further, the acquired image data is temporarily stored in the RAM 6. The CPU 4 executes programs stored in the ROM 5 and the RAM 6. Further, the data conversion table 103 and the dot pattern conversion table 105 described in FIG. 1 are stored in the ROM 5 or the RAM 6. The line buffer 21 temporarily stores binary halftone data in line units. The engine I / F 8 sends binary halftone data to the printer engine 10. The printer engine 10 prints an image on paper or the like using toner.
[0056]
The halftone data processing in the printer described above is provided by being recorded in a computer-readable recording medium such as a CD-ROM, a flexible disk (FD), or a DVD in a file in an installable format or an executable format. Can be. The halftone data processing program according to the present embodiment may be stored on a computer connected to a network such as the Internet and provided by being downloaded via the network.
[0057]
The halftone data processing program according to the present embodiment is read from the storage medium and executed by the image forming apparatus, loaded on the ROM or the RAM, and the units described in the functional configuration are generated on the ROM or the RAM. It has become so.
[0058]
Various changes or improvements may be made to the printer 100 according to the first embodiment. As an example of such a change, in the first embodiment, the dot pattern control unit 104 corrects the shape of the dot pattern using the correction information stored in the dot pattern conversion table 105. The dot pattern control unit 104 may correct the dot pattern based on an algorithm.
[0059]
For example, the dot pattern control unit 104 may rearrange the dot area into a substantially rectangular shape based on one side of the dot pattern. In this case, it is further preferable that the area of the dot area is kept substantially constant before and after the rearrangement of the dot area. More specifically, as described with reference to FIG. 5, for example, the dot pattern is divided into a plurality of sections, and based on the difference in the number of black pixels included in each section, the area of black in each section is determined. Rearrange the black areas to be equal. The algorithm used by the dot pattern control unit 104 when correcting the dot pattern may be any algorithm that corrects the dot pattern into a rectangle, and is not limited to this example.
[0060]
Another modification will be described. Even if pulse width pulse position modulation is used, the shape of the dot pattern may not be corrected to a perfect rectangle due to the limitation of the cycle of the clock in the pulse control unit 106. In this case, the priority may be given to keeping the area constant at the expense of making the dot shape rectangular. For example, it may be preferable to make the halftone shape rectangular, at the expense of keeping the area of the dot pattern constant. Furthermore, whether to give priority to keeping the area constant or to make the shape close to a rectangle may be set in advance. Thereby, a better halftone image can be obtained.
[0061]
(Embodiment 2)
In the correction information used in the image forming apparatus according to the first embodiment, dot patterns having the same area are associated as dot patterns before and after correction. On the other hand, the area of the dot pattern before correction and the area of the dot pattern after correction that are associated with each other in the correction information used in the image forming apparatus according to the second embodiment are different. That is, in the present embodiment, the dot pattern control unit 106 changes the area of the dot pattern. Other than this, the functional configuration and the hardware configuration of the printer 100 according to the second embodiment are the same as the functional configuration and the hardware configuration of the printer 100 according to the first embodiment described with reference to FIGS. The same is true.
[0062]
The correction information according to the second embodiment will be described with reference to FIG. For example, based on the dot pattern 560a having three pixels shown in FIG. 7A due to toner dust discharged by the printing unit 108, the size of the dot pattern 560a is larger than an ideal dot pattern image to be printed from the dot pattern 560a. The dot pattern image 560b may be printed. In this case, especially in a high density region, the gradation tends to be impaired, which causes a deterioration in image quality. In such a case, by reducing the size of the dot pattern, the dot gain can be suppressed, and good gradation can be maintained even in a high density area.
[0063]
The correction information according to the second embodiment associates the dot pattern 560a before correction shown in FIG. 7A with the dot pattern 570b after correction shown in FIG. 7B. Note that the area of the dot pattern 570b is smaller than the area of the dot pattern 560a. The dot pattern image 570a shown in FIG. 7B is an image printed by the printing unit 108 based on the dot pattern 570b.
[0064]
As described above, when it is known in advance that a dot pattern enlarged by a predetermined ratio as compared with the data received by the printing unit 108 is formed, the dot pattern after correction in the correction information is A dot pattern reduced by a predetermined ratio is held. As a result, halftone dots can be corrected so that an image with good gradation can be printed even in a high density area.
[0065]
Further, in the second embodiment, the dot pattern reduced by a ratio corresponding to the enlargement ratio of the dot pattern before and after the correction is used as the corrected dot pattern. However, as another example, the size of the dot pattern before and after the correction is reduced. The dot pattern reduced by the area corresponding to the difference between the dot patterns may be used as the corrected dot pattern.
[0066]
As another modification, the dot pattern conversion table 105 may be rewritable. According to this, each time the printer that outputs an image changes, the shape of the dot pattern can be corrected using data suitable for the printer.
[0067]
As another modification, the dot pattern control unit 104 may use an algorithm instead of using the correction information stored in the dot pattern conversion table 105. At this time, the algorithm used by the dot pattern control unit 104 may determine the reduction ratio of the dot pattern according to at least one of the length and shape of the boundary of the dot pattern.
[0068]
Further, in the second embodiment, the correction processing for reducing the area of the dot pattern has been described. However, as another example, the correction processing for increasing the area of the dot pattern may be performed.
[0069]
In the first and second embodiments, a printer as an image forming apparatus has been described. However, another embodiment of the present invention may be an image processing apparatus. The configuration and operation of the image processing apparatus are almost the same as the functions and operations of the printer described in the first and second embodiments. Note that the image processing apparatus according to the present embodiment does not include the printing unit 108 described in the first and second embodiments. In this point, the printer differs from the printer described in the first and second embodiments. Further, an output unit is provided in place of the printing unit 108. That is, the image processing apparatus corrects the shape of the halftone dot by processing other than the processing in the printing unit 108 described in the first or second embodiment, and the output unit transmits the corrected data to an output device or the like. Output. According to this, it is possible to improve the reproducibility of the image in the halftone data to be output from the output device.
[0070]
【The invention's effect】
As described above, according to the first aspect of the present invention, the dot pattern control means controls the on / off timing of the pulse applied to the photoreceptor so that the dot pattern control means can control the dot pattern more than the pixels forming the dot pattern. The shape of the dot pattern can be corrected using a small unit as a minimum unit. By correcting the dot pattern with a unit smaller than a pixel as a minimum unit in this manner, an effect that a high-quality image can be reproduced without increasing the data amount and without reducing the processing efficiency is obtained. Play.
[0071]
According to the second aspect of the present invention, the dot pattern control means corrects the shape of the dot pattern to a shape closer to a rectangle. Can be reproduced.
[0072]
According to the third aspect of the present invention, when correcting the shape of the dot pattern, the dot pattern control means determines the area of the dot pattern before correcting the shape and the area of the dot pattern after correcting the shape. Is kept almost constant. Therefore, by correcting the shape of the dot pattern, the area of the dot pattern changes, and accordingly, it is possible to avoid a change in the brightness indicated by the dot pattern.
[0073]
According to the fourth aspect of the invention, the dot pattern control means corrects the size of the dot pattern to a size determined based on the brightness of the dot pattern image output from the output device based on the dot pattern. be able to. Therefore, the size of the dot pattern can be corrected in accordance with the characteristics of each output device, so that the effect of maintaining good reproducibility of the original image in the dot pattern image output from the output device can be obtained. Play.
[0074]
According to the fifth aspect of the present invention, the dot pattern control means is configured to output the ideal brightness of the dot pattern image output from the output device based on the dot pattern and the dot pattern image actually output from the output device. The size of the dot pattern is reduced to a size determined according to the difference from the brightness of the dot pattern. Therefore, when the brightness of the actual dot pattern image is higher than the ideal brightness of the dot pattern image, by reducing the size of the dot pattern, the brightness of the image increases and the reproducibility of the image decreases. This has the effect of being able to suppress the problem.
[0075]
According to the sixth aspect of the present invention, the dot pattern control means controls the on / off timing of the pulse applied to the photoreceptor to minimize the unit smaller than the pixel forming the dot pattern. As a unit, the shape of the dot pattern can be corrected. By correcting the dot pattern with a unit smaller than the dot pixel as the minimum unit in this manner, good reproducibility of the image can be maintained, so that an effect of outputting a higher quality image can be obtained.
[0076]
According to the seventh aspect of the present invention, the dot pattern control means controls the ON / OFF timing of the pulse applied to the photosensitive member to minimize the unit smaller than the pixel forming the dot pattern. As a unit, the shape of the dot pattern can be corrected. By correcting the dot pattern with a unit smaller than a pixel as a minimum unit in this manner, an effect that a high-quality image can be reproduced without increasing the data amount and without reducing the processing efficiency is obtained. Play.
[0077]
According to the eighth aspect of the present invention, since the dot pattern control step corrects the shape of the dot pattern to a shape closer to a rectangle, a smoother image can be obtained by bringing the shape of the dot pattern closer to a rectangle. Can be reproduced.
[0078]
According to the ninth aspect of the present invention, the dot pattern control step includes, when correcting the shape of the dot pattern, the area of the dot pattern before the shape is corrected and the area of the dot pattern after the shape is corrected. Is kept almost constant. Therefore, by correcting the shape of the dot pattern, the area of the dot pattern changes, and accordingly, it is possible to avoid a change in the brightness indicated by the dot pattern.
[0079]
According to the tenth aspect of the invention, the dot pattern control step corrects the size of the dot pattern to a size determined based on the brightness of the dot pattern image output from the output device based on the dot pattern. be able to. Therefore, the size of the dot pattern can be corrected in accordance with the characteristics of each output device, so that the effect of maintaining good reproducibility of the original image in the dot pattern image output from the output device can be obtained. Play.
[0080]
According to the eleventh aspect of the present invention, the dot pattern control means includes: an ideal brightness of the dot pattern image output from the output device based on the dot pattern; and a dot pattern image actually output from the output device. The size of the dot pattern is reduced to a size determined according to the difference from the brightness of the dot pattern. Therefore, if the brightness of the actual dot pattern image is higher than the ideal brightness of the dot pattern image, reducing the size of the dot pattern will increase the brightness of the image and improve the reproducibility of the original image. The effect that reduction can be suppressed can be achieved.
[0081]
According to the twelfth aspect of the invention, there is an effect that any one of the operations of the seventh to eleventh aspects can be executed by a computer.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating a functional configuration of a printer according to a first embodiment;
FIG. 2 is a diagram for explaining a method of correcting the shape of a dot pattern.
FIG. 3 is a diagram showing halftone data 200 and pulse data 300.
FIG. 4 is a diagram showing pulse data 310 and a halftone image 400 after pulse width modulation.
FIG. 5 is a diagram showing pulse data 320 and a halftone image 420 after pulse position modulation.
FIG. 6 is a block diagram illustrating a hardware configuration of the printer 100.
FIG. 7 is a diagram for explaining a method of correcting the shape of a dot pattern in the dot pattern control unit 104 according to the second embodiment.
[Explanation of symbols]
3 Host I / F
4 CPU
5 ROM
6 RAM
8 Engine I / F
9 System bus
10 Printer Engine
21 line buffer
100 printer
101 Data acquisition unit
102 Data conversion unit
103 Data conversion table
104 dot pattern control unit
105 dot pattern conversion table
106 pulse control unit
108 printing section
200 halftone data
400, 420 halftone image

Claims (12)

An image processing apparatus that processes halftone data including a dot pattern according to brightness,
An image processing apparatus comprising: a dot pattern control unit that corrects the shape of the dot pattern by controlling the on / off timing of a pulse applied to a photoconductor. The image processing apparatus according to claim 1, wherein the dot pattern control unit corrects the shape of the dot pattern to a shape closer to a rectangle. The dot pattern control means, when correcting the shape of the dot pattern, keeps the area of the dot pattern before correcting the shape and the area of the dot pattern after correcting the shape substantially constant. The image processing apparatus according to claim 1, wherein: The method according to claim 1, wherein the dot pattern control unit corrects the size of the dot pattern to a size determined based on the brightness of a dot pattern image output from an output device based on the dot pattern. 4. The image processing apparatus according to claim 3, The dot pattern control unit is configured to determine an ideal brightness of a dot pattern image output from an output device based on the dot pattern and a brightness of the dot pattern image actually output from the output device. The image processing apparatus according to claim 4, wherein the size of the dot pattern is reduced to a determined size. An image forming apparatus that outputs halftone data including a dot pattern according to brightness,
A dot pattern control unit that corrects the shape of the dot pattern by controlling on / off timing of a pulse applied to the photoconductor,
An output unit configured to output the halftone data in which the shape of the dot pattern has been corrected. An image processing method for processing halftone data including a dot pattern according to lightness,
An image processing method, comprising: a dot pattern control step of correcting the shape of the dot pattern by controlling on / off timing of a pulse applied to a photoconductor. The image processing method according to claim 7, wherein the dot pattern control step corrects the shape of the dot pattern to a shape closer to a rectangle. The dot pattern control step, when correcting the shape of the dot pattern, to keep the area of the dot pattern before correcting the shape and the area of the dot pattern after correcting the shape substantially constant. 9. The image processing method according to claim 7, wherein: 8. The method according to claim 7, wherein the dot pattern control step corrects the size of the dot pattern based on the dot pattern to a size determined based on the brightness of a dot pattern image output from an output device. 10. The image processing method according to any one of claims 1 to 9. The dot pattern control step is determined according to a difference between an ideal brightness of a dot pattern image output from an output device based on the dot pattern and a brightness of the dot pattern image actually output from the output device. The image processing method according to claim 10, wherein the size of the dot pattern is reduced by a ratio. A program for causing a computer to execute the image processing method according to claim 7.

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