JP4774914B2 - Image processing apparatus and image processing method - Google Patents

Description

  The present invention relates to an image processing apparatus that reproduces a document created by a host computer, a personal computer for various DTPs (desk top publishing), or the like by an image forming apparatus.

  In recent years, hardware and software for multimedia and DTP have dramatically improved, and office documents and various electronic documents (including drawings and photographic images) for other purposes have become very complicated. Further, there is an increasing demand for outputting them at higher speed, higher image quality, and more easily with various image forming apparatuses. In response to such a request, various various image processing apparatuses have been developed. A typical one of them receives documents generated by PDL (Page Description Language) etc. by various standard interfaces (Ethernet (registered trademark) / SCSI / GPIB / serial / Centronics / AppleTalk (registered trademark), etc.) There is an image processing apparatus for interpreting a received PDL file and reproducing it faithfully in a target image forming apparatus. The image processing apparatus is typically one that is applied to an image forming apparatus such as an electrophotographic system or an inkjet system.

  Recently, color printers have been widely used as image forming apparatuses, and there are a wide variety of image processing apparatuses that interpret image data generated by interpreting the PDL file described above and that are compatible with color printers. The image processing apparatus used in this color printer has an image expansion means for interpreting a PDL file and performing expansion processing, and a binary or multi-value full-page image memory, and the image memory is temporarily rasterized. There is a method of forming an image and sending a raster image to a printer.

  In a conventional image processing apparatus, for example, as a 400 page (dot / inch) A3 size one page full page image memory, a binary value of 4 megabytes and a single pixel multivalued (8 bits) have a capacity of 32 megabytes. is required. In the case of a color image, four color pages of K (black), Y (yellow), M (magenta), and C (cyan) are required, so a large amount of image memory of 128 megabytes is required. . In general, when developing a multi-valued image and generating an image in an image processing apparatus having a binary image memory, an area gradation method such as dithering or an error diffusion method is often used. In an image forming apparatus that handles multi-valued images, for example, each image has 256 tones with 8 bits, and in the case of a color image, K (black), Y (yellow), M (magenta), and C (cyan). A typical example is 8 bits for each color and 32 bits per pixel.

Here, a multi-value system is employed in a high-function / high-performance (high-end) printer system for the purpose of high image quality. A characteristic of the flow of image processing (image path) in this multi-value system is that, for example, JPEG (Joint Photographic Coding Experts Group) is used to match the output timing after rasterization that develops character or image data into raster data. ) Etc. are used to perform multi-value compression / decompression. Then, image data is sent to the printer engine control unit, and screen processing is performed by the printer engine control unit.
In the prior art described in the patent document, a process of switching a screen for each object by adding a tag to each object is performed for the purpose of achieving both image quality of a photographic part and a character part (see, for example, Patent Document 1).
Other patent documents disclose a technique having an optimal compression parameter for each screen according to the screen parameters (see, for example, Patent Document 2).

JP-A-8-235346 JP-A 64-047169

  On the other hand, low-function, low-performance (low-end) printer systems often employ binary systems for the purpose of cost reduction and speedup. A characteristic of the image path in this binary system is that, after rasterization, screen processing (binarization) is performed in the controller, and binary by, for example, JBIG (Joint Bi-level Image experts Group) to match the output timing. Compression / decompression is performed and image data is sent to the printer engine controller.

  Here, even in this binary system, as in the above-described multi-value system, if the screen is switched for each object, both the character portion and the photograph portion should be compatible. However, if a lot of images with different spatial frequencies are mixed in the binarized image data, the binary compression processing is executed after the screen processing, so that the compression rate and processing speed are slow depending on the periodic structure of the screen. There are cases where the system fails. For this reason, in a binary printer system, switching screens within the plane has hardly been performed. In addition, the higher the speed, the more the productivity is affected (the delay in print output due to the delay in image processing), and there are cases where even screen switching depending on the mode fails. For example, as described in Patent Document 2, it is only necessary to have an optimal compression parameter for each screen according to the screen parameter. However, for example, when the screen is frequently switched in a plane, it cannot be a practical method.

  The present invention has been made to solve the technical problems as described above, and its object is to break down the compression rate and productivity in, for example, an ultra-high speed binary printer system. Without switching, it is possible to switch screens for each mode or for each object.

The above object, the present invention provides an image processing apparatus for performing image processing of an inputted color image data, with respect to the color image data input, different each mode from among a plurality of screens comprising a screen processing unit to perform the screen processing by using a screen, and a screen processing is to perform compression and / or decompression processing on the run color image data compression / expansion processing unit by the screen processing unit, the screen When a screen having a different screen line number for each mode is used in the processing unit, the two-dimensional space vector corresponding to the screen line number of the screen parameter for each color has the same vector direction and length between the screen line numbers. Is an integer multiple, and this compression / decompression processing unit is a part of the screen used in the screen processing unit. It is characterized by be implemented to optimize the frequency components of the compression parameter in the spatial frequency characteristic of the lowest screen parameters Luo screen ruling.

In addition, when a screen having a different screen line number for each mode is used in the screen processing unit, the sum / difference vector of the two-dimensional space vector corresponding to the screen line number of the screen parameter for each color is calculated between the screen line numbers. The compression / decompression processing unit optimizes and implements the frequency component of the compression parameter to the spatial frequency characteristic of the screen parameter having the lowest screen line number among the screens used in the screen processing unit. It may be characterized in that.
Further, when a screen having a different screen line number for each mode is used in the screen processing unit, a two-dimensional space vector corresponding to the screen line number of the screen parameter for each color and a two-dimensional space vector of another screen line number The vector direction is the same and the length is an integer multiple between each line number, and the compression / decompression processing unit has a screen line number from among the screens used in the screen processing unit. It can be characterized in that the frequency component of the compression parameter is optimized and mounted on the spatial frequency characteristic of the lowest screen parameter .

From another viewpoint, the present invention provides an image processing apparatus for performing image processing of an inputted color image data, with respect to the color image data inputted from the plurality of screens, the same surface A screen processing unit that executes screen processing using a different screen for each object in the screen, and compression / decompression that performs compression and / or expansion processing on the color image data on which the screen processing is executed by the screen processing unit When a screen having a different number of screen lines for each object is used in this screen processing unit, a two-dimensional space vector corresponding to the screen line number of the screen parameter for each color is obtained between the screen line numbers. The vector direction is the same and the length is an integer multiple, and the compression / decompression processing unit Screen ruling from the need the screen is characterized by be implemented to optimize the frequency components of the compression parameter in the spatial frequency characteristic of the lowest screen parameters.

In addition, when a screen having a different screen line number for each object is used in the screen processing unit, the sum / difference vector of the two-dimensional space vector corresponding to the screen line number of the screen parameter for each color is calculated between the screen line numbers. The compression / decompression processing unit optimizes and implements the frequency component of the compression parameter to the spatial frequency characteristic of the screen parameter having the lowest screen line number among the screens used in the screen processing unit. It may be characterized in that.
Further, when a screen having a different screen line number for each object is used in the screen processing unit, a two-dimensional space vector corresponding to the screen line number of the screen parameter for each color and a two-dimensional space vector of another screen line number The vector direction is the same and the length is an integer multiple between each line number, and the compression / decompression processing unit has a screen line number from among the screens used in the screen processing unit. It can be characterized in that the frequency component of the compression parameter is optimized and mounted on the spatial frequency characteristic of the lowest screen parameter .

In addition, the image data is binarized by the screen processing in the screen processing unit, and the compression / decompression processing unit performs compression and / or expansion processing on the binarized color image data.
Further, the screen processing unit can be characterized in that the screen is switched for each color of the input color image data and the screen processing is executed for each color.

On the other hand, the present invention is an image processing method for performing image processing on input color image data, wherein two-dimensional space vectors corresponding to the number of screen lines of screen parameters for each color or screens for each color. Sum or difference vectors of two-dimensional space vectors corresponding to the number of lines, or a sum or difference vector of two-dimensional space vectors corresponding to a specific number of screen lines for each color and two-dimensional space vectors of other screen lines However, a plurality of screen patterns in which the vector direction is the same between the screen line numbers and the length is an integer multiple is stored in the memory, and the input is performed using the plurality of screen patterns stored in the memory. color image for each mode for data, or for each object in the same plane, subscriptions with different screen ruling of the screen Running down process, with respect to the screen processing color image data which has been performed, the frequency of the compression parameters in the spatial frequency characteristic of the lowest screen parameters screen frequency from a plurality of screen pattern used to screen processing It is characterized by optimizing components and applying compression and / or expansion processing.

  According to the present invention, even in a binary printer, it is possible to achieve both character / photo image quality, and a system with improved image quality and productivity can be provided.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a diagram showing an overall configuration of a printer system to which the present embodiment is applied. Here, an image forming apparatus 1 that develops an image of input electronic document information and prints it on paper, and a client PC (personal computer) 2 that is a host computer that provides the electronic document to the image forming apparatus 1. Is shown. The image forming apparatus 1 may receive image data from an image reading apparatus (IIT) (not shown) other than the client PC 2.

The image forming apparatus 1 includes, for example, an image processing unit (IPS: Image Processing System) 10 that performs predetermined image processing on image data of an electronic document output from a client PC 2 and a so-called tandem type that uses an electrophotographic method. And a marking engine 30 which is a digital color printer. The marking engine 30 includes image forming units 31Y, 31M, 31C, and 31K including a plurality of engines arranged in parallel at regular intervals in the horizontal direction. The image forming units 31Y, 31M, 31C, and 31K form yellow (Y), magenta (M), cyan (C), and black (K) toner images, and sequentially transfer them onto a sheet. The four image forming units 31Y, 31M, 31C, and 31K are respectively an image carrier (photoconductor) that forms an electrostatic latent image and carries a toner image, and a surface of the photoconductor drum 32. A charger 33 for uniformly charging the photosensitive drum 32, an exposure device 34 for exposing the photosensitive drum 32 charged by the charger 33, and a developing device 35 for developing the electrostatic latent image obtained by the exposure device 34. Further, a transfer roll 36 for transferring a toner image formed on the surface of the photosensitive drum 32 onto a sheet is provided. The marking engine 30 includes a sheet conveying belt 37 that conveys the sheet to a transfer position formed by the photosensitive drum 32 and the transfer roll 36 of each of the image forming units 31Y, 31M, 31C, and 31K. Further, a fixing device 38 for fixing the toner image transferred onto the paper is provided.
In addition, it is possible to grasp only the image processing unit 10 as an image processing apparatus instead of including the entire image forming apparatus 1.

Each of the image forming units 31Y, 31M, 31C, and 31K includes substantially the same components except for the toner stored in the developing unit 35. Image data input from the client PC 2 is subjected to image processing by the image processing unit 10 and supplied to the marking engine 30 through a predetermined interface. The marking engine 30 operates based on a control signal such as a synchronization signal supplied from an image output control unit (not shown). First, the yellow (Y) image forming unit 31 </ b> Y generates an electrostatic latent image on the surface of the photosensitive drum 32 charged by the charger 33 by the exposure device 34 based on the image signal obtained from the image processing unit 10. Form. A yellow (Y) toner image is formed on the electrostatic latent image by the developing unit 35, and the formed yellow (Y) toner image is a sheet on the sheet conveying belt 37 that rotates in the direction of the arrow in the figure. Is transferred using a transfer roll 36. Similarly, magenta (M), cyan (C), and black (K) toner images are formed on the respective photosensitive drums 32 and are multiple-transferred onto a sheet on a sheet conveying belt 37 using a transfer roll 36. The The multiple transferred toner images on the paper are conveyed to a fixing device 38 and fixed on the paper by heat and pressure.
The marking engine 30 of the image forming apparatus 1 shown in FIG. 1 employs a configuration in which toner images are sequentially transferred onto the conveyed paper, but a so-called intermediate transfer belt is employed instead of the paper conveying belt 37. It is also possible to employ a so-called secondary transfer type image forming apparatus in which the toner images are transferred onto the intermediate transfer belt in a multiple transfer and then subjected to secondary transfer on the paper at once.

Next, an image processing method that is a characteristic configuration of the present embodiment will be described.
FIG. 2 is a block diagram illustrating a configuration of the image processing unit 10 to which the exemplary embodiment is applied. The image processing unit 10 mainly includes a controller 11 and an engine control unit 12. The controller 11 includes a PDL interpretation unit 21 that interprets a PDL (page description language) sent from the client PC 2 as a command, and a drawing unit that converts a color signal (RGB) specified by PDL into a color signal (YMCK) of the marking engine 30. 22. In addition, a rendering unit 23 that renders the intermediate code rendered at the time of rendering into image data compatible with the marking engine 30; a screen processing unit 24 that performs screen processing (binarization processing) on the rendered image; It has. Further, a binary compression / decompression unit 25 that performs binary compression / decompression processing to match the output timing of the screen processed image is provided. The screen processing unit 24 includes a pattern storage unit 26 that stores various patterns used when screen processing is executed. On the other hand, the engine control unit 12 includes a pulse width modulation unit 27 that performs pulse width modulation on the screened image data.

  As described above, in this embodiment, after the screen processing is performed by the screen processing unit 24, the binary compression / decompression unit 25 performs compression / expansion in order to match the output timing. Therefore, when screen processing executed by the screen processing unit 24 is performed, the selection of the screen parameter is devised, so that, for example, even when the screen is different for each object in one plane, the compression breakage is performed. Can be avoided.

This will be described in further detail.
FIG. 6 is a diagram illustrating an example of image processing in a color multi-value printer. FIG. 6 is used for comparison with the color binary printer shown in FIG. 2 of the present embodiment. The controller 201 of the image processing unit 200 shown in FIG. 6 compresses / decompresses, for example, 600 dpi 8-bit multi-value, after rendering processing by the rendering unit 23, with multi-value compression / decompression unit 211 as multi-value data. Processing is executed. Then, for example, image data is output to the engine control unit 202 via an 8-bit multi-value interface (I / F). In the engine control unit 202, the screen processing unit 212 executes screen processing. In this screen processing unit 212, even when complicated processing such as switching screens for each object is performed, for example, multi-value compression such as JPEG has already been performed, and compression processing before a period is not performed. Therefore, various processes can be executed without any particular problem.

  On the other hand, in this embodiment, for example, in a low-end model, binary processing is performed at an early stage to simplify the configuration and reduce costs. For this purpose, as shown in FIG. 2, the screen processing unit 24 of the image processing unit 10 performs screen processing and binarizes, and then the binary compression / decompression unit 25 performs compression / decompression. In this case, since the screen has a periodic structure, the compression / expansion in the binary compression / expansion unit 25 is executed with an optimal compression parameter suitable for the periodic structure. For example, in the current model, regardless of the object, for example, screen parameters of 200 lines are all selected in the plane, and the processing is executed using compression parameters with a period that is compatible with the 200 lines. It was. However, as is done in color multi-value printers, for example, the number of lines is increased for characters and lines, and for example, the number of lines is decreased for images and graphics in order to increase graininess and gradation. If you want to change the number of lines for each object such as text, image, graphics, etc., even if the compression parameter is optimized for any one screen, problems such as productivity and compression rate on other screens It was not possible to optimize. Therefore, in this embodiment, even when the screen is switched for each object, it is possible to avoid failures such as fallback even when compressing after screen processing by selecting compatible screen parameters. It is said. Here, the fallback means that the processing is performed several times by switching the parameter when a failure occurs in the image processing or the like. If this fallback is repeated several times, it will be aborted if it fails. Raising this abort is a big problem, but fallback also reduces productivity, so it is preferable not to raise it.

  FIGS. 3A to 3C are diagrams for explaining examples of screen components effective for avoiding compression failure. 3A has screen components of 134 lines and 26 degrees, FIG. 3B has screen components of 189 lines and 18 degrees, and FIG. 3C has screen components of 268 lines and 26 degrees. Each arrow indicates a frequency vector of the screen, and a basic component is indicated by a solid line and a diagonal component (secondary component) is indicated by a dotted line. One of the diagonal components (secondary components) is a sum vector of basic vectors, and the other is a difference vector. In FIG. 3A, the sum vector is indicated by a dotted line, and in FIG. 3C, both the sum vector and the difference vector are indicated. Here, the screen component shown in FIG. 3A has a spatial distance twice as large as the basic component of 268 lines and 26 degrees shown in FIG. In addition, the diagonal component (secondary component) of 268 line 26 degrees shown in FIG. 3C matches the basic component of the screen shown in FIG.

  In the present embodiment, the screen processing unit 24 in FIG. 2 reads a predetermined pattern from a pattern storage unit 26 in which patterns as shown in FIGS. 3A to 3C are stored, for example. The screen processing is executed using. At this time, in the screen processing, for example, the screen is switched in one surface such as one surface for each of the colors Y, M, C, and K of the A4 image to be printed. It can be processed on different screens according to the following. For example, 268 lines for characters, 189 lines for images, 134 lines for graphics, and the like. It is also possible to change the screen for each mode such as a photo mode, a character mode, and a map mode. Furthermore, the screen parameters can be changed for each color. The mode is determined by, for example, a mode selection operation performed by a user who uses the image forming apparatus 1.

In this embodiment, any one of the following relationships is used as the screen to be switched.
1) A two-dimensional space vector (basic vector) of screen parameters for each color is in an integer multiple (the same vector direction and length is an integral multiple) between the numbers of lines.
2) The sum / difference vector of the two-dimensional space vectors (basic vectors) of the screen parameters for each color has an integer multiple (the same vector direction and the integral length) between the numbers of lines.
3) The two-dimensional space vector (basic vector) of the screen parameters for each color and the sum / difference vector of the basic vectors of other lines are integer multiples between the lines (the vector direction is the same and the length is an integer) Times).

3 (a) and 3 (c) have the relationship of 1) above, that is, the spatial frequency of the basic vector is doubled. 3 (b) and FIG. 3 (c) have the above relationship 3), that is, the sum / difference vector of line 268 in FIG. 3 (c) and the basic vector of line 189 in FIG. 3 (b). They are in an equal relationship. Then, for example, FIG. 3C is selected for characters, FIG. 3B is selected for images, and FIG. 3A is selected for graphics. These screens have a relationship in which the primary component / secondary component of the spatial frequency of the screen is N times (N is a positive integer). According to this, by selecting a specific compression parameter and compressing it by the binary compression / decompression unit 25, it becomes possible to maintain good productivity and compression rate.
Here, the “basic vector” of the spatial frequency is a vector in the case where the same adjacent pixels in the screen are connected and one of them is set as the start point and the other is set as the end point.

  FIG. 4 is a diagram illustrating an example of the binary compression / decompression unit 25, and illustrates an example of binary compression by JBIG. In JBIG shown in FIG. 4, resolution reduction conversion (PRES) 251, typical prediction (TP) 252, deterministic prediction (DP) 253, model template (MT) 254, adaptation template (AT) 255, An arithmetic encoder (AC) 256. Here, each pixel constituting the digital image has a strong correlation with a neighboring pixel adjacent to this pixel. In the JBIG system shown in FIG. 4, when a certain target pixel is encoded, the pixel value is predicted with reference to a pattern of neighboring pixel values of the target pixel. Here, if the prediction is correct, there is no need to describe the target pixel in the data, and as a result, the data length can be shortened. Here, a pattern of neighboring pixel positions referred to at the time of prediction is called a template.

  In this embodiment, the frequency component of the compression parameter is optimized and mounted on the spatial frequency characteristic of the minimum number of lines (long period). More specifically, by adjusting the AT value, which is a parameter in the adaptive template 255 shown in FIG. 4, to the minimum line number cycle, for example, the line number is switched for each object. Can be compressed well. In the example shown in FIG. 3, the cycle is set to 134 lines.

Next, an image processing method to which the present embodiment is applied will be described.
FIG. 5 is a flowchart showing a flow of image processing executed by the client PC 2, the image processing unit 10, and the marking engine 30. Steps 102 to 110 are processes executed in the image processing unit 10.
First, the printer driver of the client PC 2 converts a command from the application into a PDL (page description language) which is a printer drawing command (step 101). The PDL drawing command is sent from the client PC 2 to the image forming apparatus 1. In the image processing unit 10 of the image forming apparatus 1, the PDL interpretation unit 21 interprets the acquired PDL command (step 102). . Thereafter, the drawing unit 22 converts the color signal (RGB) specified by the interpreted PDL into the color signal (YMCK) of the marking engine 30 (step 103). When rendering is performed by the rendering unit 22, raster data is converted into the engine resolution of the marking engine 30, and characters and graphics are rendered with an intermediate code of the engine resolution (step 104). Further, when rendering is performed by the rendering unit 22, an operation of attaching the object Tag to each of raster / character / graphics is performed (step 105). This Tag corresponds to each pixel.

  Thereafter, the rendering unit 23 renders the intermediate code into image data suitable for the marking engine 30 (step 106). The rendered image is subjected to screen processing (binarization processing) by the screen processing unit 24 (step 107). This screen processing is performed at a desired spatial frequency (for example, 150 lines / 200 lines / 300 lines) according to the object Tag described above. Also, as described above, if the spatial frequency of the screen is different, compatibility with the binary compression / decompression processing in the subsequent stage is deteriorated. Therefore, various screen parameters are implemented with restrictions. Examples of the constraint include the above-described 1) to 3). Examples of satisfying such a constraint include 134 lines / 189 lines / 268 lines as shown in FIGS. These screen patterns are stored in the pattern storage unit 26, and the screen processing unit 24 reads the screen pattern having a desired spatial frequency from the pattern storage unit 26 and executes the process.

  Thereafter, the binary compression / decompression unit 25 performs binary compression / decompression of the screen-processed image (step 108). At this time, the compression parameters are optimized with the screen parameters having the minimum number of lines. In the present embodiment, the JBIG method as shown in FIG. 4 is used, but other compression methods can be selected if binary compression is used. The image data processed by the binary compression / decompression unit 25 is input to the pulse width modulation unit 27 of the engine control unit 12. In the pulse width modulation unit 27, the image data screened by the controller 11 is modulated as a pulse signal (step 109). Then, the pulse-modulated image data is output to the marking engine 30 (step 110). In the marking engine 30 that has acquired the image data, a color image is formed on the paper by each component as shown in FIG. 1 and printed out (step 111).

  As described above in detail, in this embodiment, by giving conditions to the screen parameters, even in an ultra-high-speed binary printer system, each mode or object can be used without causing the compression rate or productivity to break down. You can switch screens every time. That is, according to the present embodiment, it is possible to provide a system that achieves both character / photo image quality compatibility and image quality and productivity even in a binary printer.

1 is a diagram illustrating an overall configuration of a printer system to which the exemplary embodiment is applied. It is a block diagram which shows the structure of the image process part to which this Embodiment is applied. (A)-(c) is a figure for demonstrating the example of a screen component effective in order to avoid a compression failure. It is the figure which showed an example of the binary compression / decompression part. It is the flowchart which showed the flow of the image processing performed by client PC, an image process part, and a marking engine. It is a figure showing an example of image processing in a color multi-value printer.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus, 2 ... Client PC (personal computer), 10 ... Image processing part (IPS), 11 ... Controller, 12 ... Engine control part, 24 ... Screen processing part, 25 ... Binary compression / decompression part, 26 ... Pattern storage

Claims (9)

An image processing apparatus that performs image processing on input color image data,
A screen processing unit that executes screen processing using different screens for each mode from among a plurality of screens for the input color image data;
A compression / decompression processing unit that performs compression and / or expansion processing on color image data that has undergone screen processing by the screen processing unit ,
When the screen processing unit uses screens having different screen line numbers for each mode, the two-dimensional space vector corresponding to the screen line number of the screen parameter for each color has the same vector direction between the screen line numbers. And the length is an integer multiple,
The compression / decompression processing unit is implemented by optimizing the frequency component of the compression parameter and mounting the spatial frequency characteristic of the screen parameter having the lowest screen line number among the screens used in the screen processing unit. Processing equipment. An image processing apparatus that performs image processing on input color image data,
A screen processing unit that executes screen processing using different screens for each mode from among a plurality of screens for the input color image data;
A compression / decompression processing unit that performs compression and / or expansion processing on color image data that has undergone screen processing by the screen processing unit ,
When the screen processing unit uses screens with different screen line numbers for each mode, the sum / difference vector of the two-dimensional space vectors corresponding to the screen line numbers of the screen parameters for each color is calculated between the screen line numbers. It is an integer multiple relationship,
The compression / decompression processing unit is implemented by optimizing the frequency component of the compression parameter and mounting the spatial frequency characteristic of the screen parameter having the lowest screen line number among the screens used in the screen processing unit. Processing equipment. An image processing apparatus that performs image processing on input color image data,
A screen processing unit that executes screen processing using different screens for each mode from among a plurality of screens for the input color image data;
A compression / decompression processing unit that performs compression and / or expansion processing on color image data that has undergone screen processing by the screen processing unit ,
When a screen having a different screen line number for each mode is used in the screen processing unit, a two-dimensional space vector corresponding to the screen line number of the screen parameter for each color and a two-dimensional space vector of another screen line number The sum / difference vector has the same vector direction and the length is an integral multiple between the number of lines.
The compression / decompression processing unit is implemented by optimizing the frequency component of the compression parameter and mounting the spatial frequency characteristic of the screen parameter having the lowest screen line number among the screens used in the screen processing unit. Processing equipment. An image processing apparatus that performs image processing on input color image data,
A screen processing unit that executes screen processing using different screens for each object in the same plane from among a plurality of screens for the input color image data;
A compression / decompression processing unit that performs compression and / or expansion processing on color image data that has undergone screen processing by the screen processing unit ,
When the screen processing unit uses screens having different screen line numbers for each object, the two-dimensional space vector corresponding to the screen line number of the screen parameter for each color has the same vector direction between the screen line numbers. And the length is an integer multiple,
The compression / decompression processing unit is implemented by optimizing the frequency component of the compression parameter and mounting the spatial frequency characteristic of the screen parameter having the lowest screen line number among the screens used in the screen processing unit. Processing equipment. An image processing apparatus that performs image processing on input color image data,
A screen processing unit that executes screen processing using different screens for each object in the same plane from among a plurality of screens for the input color image data;
A compression / decompression processing unit that performs compression and / or expansion processing on color image data that has undergone screen processing by the screen processing unit ,
When a screen having a different screen line number is used for each object in the screen processing unit, a sum / difference vector of two-dimensional space vectors corresponding to the screen line number of the screen parameter for each color is calculated between the screen line numbers. It is an integer multiple relationship,
The compression / decompression processing unit is implemented by optimizing the frequency component of the compression parameter and mounting the spatial frequency characteristic of the screen parameter having the lowest screen line number among the screens used in the screen processing unit. Processing equipment. An image processing apparatus that performs image processing on input color image data,
A screen processing unit that executes screen processing using different screens for each object in the same plane from among a plurality of screens for the input color image data;
A compression / decompression processing unit that performs compression and / or expansion processing on color image data that has undergone screen processing by the screen processing unit,
When a screen having a different screen line number for each object is used in the screen processing unit, a two-dimensional space vector corresponding to the screen line number of the screen parameter for each color and a two-dimensional space vector of another screen line number The sum / difference vector has the same vector direction and the length is an integral multiple between the number of lines.
The compression / decompression processing unit is implemented by optimizing the frequency component of the compression parameter and mounting the spatial frequency characteristic of the screen parameter having the lowest screen line number among the screens used in the screen processing unit. Processing equipment. The binarized by the screen processing in the screen processing unit, the compression / decompression processing unit, according to claim 1 to 6, characterized by applying compression and / or decompression processing on the binarized color image data The image processing apparatus according to claim 1. The screen processing unit switches the screen for each color of the color image data input, image processing apparatus according to claim 1 to 7 any one of claims, characterized in that to perform the screen processing for each color. An image processing method for performing image processing on input color image data,
Two-dimensional space vectors corresponding to the screen line number of the screen parameter for each color , or the sum or difference vector of two-dimensional space vectors corresponding to the screen line number for each color , or a specific screen line number for each color A plurality of screens in which the sum or difference vector of the two-dimensional space vectors corresponding to the two-dimensional space vectors of the other screen lines is the same in the vector direction and the length is an integral multiple between the screen lines Store the pattern in memory,
Using the plurality of screen patterns stored in the memory, the input color image data is screened using screens having different screen line numbers for each mode or for each object in the same plane. Execute the process,
Compresses color image data that has undergone screen processing by optimizing the frequency component of the compression parameter to the spatial frequency characteristics of the screen parameter with the lowest screen line number from among the plurality of screen patterns used for screen processing. And / or performing an expansion process.

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