JP2005110151A - Image processing method, image processing system, and image processing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce a processing time at the time of color image output in a color copying apparatus equipped with a tandem type engine. <P>SOLUTION: A color of Y having the least influence on image quality based on human vision property is treated as a primary color out of output colors Y, M, C, K, and hereinafter the following output process is carried out from color of M to color C and color K. While a normal process is carried out in a system, in which an image path passing through an image processing unit 20 is bypassed at an intermediate switching unit 801b to the side of a page memory processing device 910, and then the image pass is turned again through the intermediate switching unit 801b to the original image path, the images of color of M, color of C and color of K are subjected to prescribed image processes. The color of Y is subjected to a through print processing, which omits the bypass of the image path and does not pass through a page memory processing device 910. In this way, the image process can be carried out by absorbing a tandem gap between the color of Y and the color of M so that an output processing time FCOT after emitting an output command until output object is ejected can be shortened. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an image processing method used for forming a color output image corresponding to a color input image on a predetermined output medium after performing desired image processing on the color input image, and the image processing method. The present invention relates to an image processing system to be implemented and an image processing apparatus constituting the image processing system.

  For example, after a desired image processing is performed on an input color image, such as a printer, a facsimile machine, a copying machine, or a multi-function machine having a plurality of these functions, a color output image corresponding to this color image is output as a predetermined output. There is an image forming apparatus that forms on a medium.

For example, in the case of an image forming apparatus that supports color output, RGB (or Lab (correctly L ^* a ^* b ^* )) image data obtained by reading a document is used as a color suitable for subtractive color mixing according to the output side. Convert to signal. For example, at least three (preferably four) from the Lab color system represented by the Lab signal, for example, the YMC color system represented by each color signal of yellow (Y), magenta (M), and cyan (C) Mapping processing to a system or a CMYK color system with black (K) added thereto generates raster data that has been color-separated for print output. This raster data is sent to a print engine that forms an image corresponding to the read original image on the printing paper. The print engine forms an image on printing paper of a predetermined size based on the received raster data.

  The configuration of the engine unit, which is a main part related to image formation of the image forming apparatus, is, for example, one that forms a color image by repeating the same image forming process for each output color of K, Y, M, and C. There is a multi-pass type (cycle type) color image forming apparatus in which an image of each color is sequentially formed by one engine (photoreceptor unit) and a color image is formed by superimposing and transferring the images one by one to an intermediate transfer member. . This multi-pass type color image forming apparatus needs to superimpose and transfer one color at a time to the intermediate transfer member when outputting a color image, and the number of output colors is four times as large as when outputting a monochrome image (four times in the previous example). The output processing time FCOT (First Copy Out Time) from when the output command is issued until the output is discharged becomes long, and the productivity is inferior.

  In order to further shorten the output processing time FCOT when outputting this color image, a plurality of engines corresponding to each output color are arranged in-line in the order of K → Y → M → C, for example, K, Y, M , C images are processed in parallel (simultaneously) by four engines (see Patent Documents 1 and 2).

JP-A-8-65530 JP 2000-261676 A

  In the case of this tandem type color image forming apparatus, a plurality of engines corresponding to the respective output colors are arranged at regular intervals (so-called tandem gap), and images corresponding to the respective output colors are sequentially arranged at the time of image formation. It is necessary to pass to the engine corresponding to each output color at regular intervals. For this reason, an image memory (page memory) that holds images in page units corresponding to each output color is essential.

  At this time, in order to reduce the memory capacity, generally, the image is compressed and stored in the image memory, and the compressed image read from the image memory is subjected to a decompression process corresponding to the compression process to obtain the original. The image is restored. Here, various methods have been proposed as image compression / expansion methods. For example, if four colors such as K, Y, M, and C are handled as output colors, they are described in Patent Document 3. Can be used.

JP-A-5-236280

  However, although the tandem configuration reduces the processing time FCOT when outputting a color image as compared with the multi-pass type by simultaneously performing image processing on an image corresponding to a plurality of output colors, Image data must be formed by passing image data to the engine for each output color sequentially at regular intervals corresponding to the interval between engines (tandem gap), and there is a limitation in processing time due to the tandem gap. To do. For this reason, when higher-speed image forming processing (that is, productivity) is required, limitation of processing time due to the tandem gap becomes a problem.

  The present invention has been made in view of the above circumstances, and has an image processing method that is excellent in productivity and can be applied to a dandem type, an image processing system that implements the image processing method, and an image processing system. An object of the present invention is to provide an image processing apparatus.

  That is, in the image processing method according to the present invention, one of a plurality of color components constituting a color image (preferably a component that has little influence on the image quality due to human visual characteristics) is more than normal processing. Processing that can be performed in a short time is executed, and the normal processing is executed for the other color component of the plurality of color components.

  For example, when processing for the other color component is performed using a system for performing a desired process at the switching destination where the image path is switched and then returning to the image path as a normal process, a process for switching the image path is performed for one color component. By omitting, processing (high-speed processing) that can be performed in a shorter time than normal processing is executed. Note that the desired processing performed at the switching destination where the image path is switched may be to perform image processing related to image quality improvement on the color image at the switching destination, or to the color image input at the switching destination. Alternatively, a compression process may be performed, temporarily stored in the image memory, and then a process of performing a decompression process corresponding to the compression process may be performed on the color image read from the image memory. In the latter case, it is preferable to execute processing that can be performed in a short time by omitting compression processing and expansion processing for one color component.

  Also, when handling a color image representing a document read by a predetermined reading device, such as a copying apparatus, detection processing for detecting ground color information of the document with an emphasis on accuracy is performed as a normal process. It is preferable to perform processing that can be performed in a short time by performing processing for the component and executing detection processing that emphasizes the detection speed of the background color information of the original for one color component.

  In this case, for one of the color components, the detection process that emphasizes the detection speed of the background color information of the original is executed, and the detection process that detects the background color information of the original is executed with an emphasis on accuracy, and the detection speed is emphasized. When the processing to form a color output image (for example, on the output medium) is started based on the processed image using the detected result, and the detection result that emphasizes accuracy is obtained, the detection result that emphasizes detection speed It is preferable to switch to a detection result that emphasizes accuracy, and to form a color output image based on a processed image using the detection result that emphasizes accuracy.

  An image processing system according to the present invention is a system that implements the image processing method according to the present invention, and is an ordinary one of a plurality of color components used to form a color output image. A first processing unit that executes processing that can be performed in a shorter time than processing; and a second processing unit that executes the normal processing for the other color component of the plurality of color components. It was supposed to be.

  If each image forming unit corresponding to a plurality of color components is arranged in a tandem type, the first processing unit executes processing for one color component and the one color component Is formed on the output medium by the image forming unit corresponding to the one color component, and then the second processing unit executes processing for the other color component to display the image represented by the other color component. It is desirable to form the image to be formed on the output medium by the image forming unit corresponding to the other color component.

  The image processing apparatus according to the present invention is suitable for configuring the image processing system according to the present invention. In addition, the invention described in the dependent claims defines further advantageous specific examples of the image processing method, the image processing system, or the image processing apparatus according to the present invention.

  The image processing method, the image processing system, or the image processing apparatus according to the present invention can be realized by software using an electronic computer (computer), and a program for this and a recording medium storing the program are used as inventions. It is also possible to extract. Note that the program may be provided by being stored in a computer-readable storage medium, or may be distributed via wired or wireless communication means.

  According to the present invention, in a color image-compatible image forming apparatus (for example, a copying apparatus or a printing apparatus), one of the plurality of color components used for outputting a color image is subjected to normal processing. Since the processing that can be performed in a short time is executed and the normal processing is executed for the other (all but one), a plurality of image forming units (engines) corresponding to the respective color components are provided. Even in a tandem type color image forming apparatus, it is possible to perform image processing by absorbing a tandem gap, and the output processing time from when a color image output command is issued until the output is discharged, One color component is shortened compared to the configuration in which normal processing is executed for all color components by the amount of processing that can be performed in a shorter time than normal processing. Can.

  For example, when normal processing is performed for a system in which a desired process is performed at the switching destination where the image path is switched and then returned to the original image path, the image path can be shortened for one color component. Output processing time can be shortened.

  In addition, in the case of a configuration that includes a process of performing compression processing at the switching destination and temporarily storing the image in the image memory and then decoding (decompressing) the image read from the image memory, the compression processing for one color component and the By omitting the corresponding decoding process, the output processing time can be shortened compared to the case of performing the compression process and the corresponding decoding process.

  Also, in the case of a configuration that performs ground color removal processing or density adjustment processing based on the result of detecting the ground color information of the document, emphasizing ground color detection performance and ground color removal performance, Although it takes a long time to acquire, it is a normal process to execute ground color removal processing that can detect ground color information with high accuracy. By executing processing based on excellent ground color detection processing, output processing for one color component can be started before highly accurate ground color information is detected, and the output processing time is shortened accordingly. be able to.

  In addition, if switching to processing using this highly accurate ground color information is performed at the time when high-accuracy ground color information is detected during the output processing for one color component, one color component after the switching Can be equivalent to the image quality of other color components.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a mechanism diagram of an example of a color copying apparatus equipped with an image processing unit which is an embodiment of an image processing apparatus according to the present invention. The color copying apparatus 1 includes an image acquisition unit 10, an image processing unit 20, an image output unit 30, and a platen cover 60. The image processing unit 20 is provided at a boundary portion between the image acquisition unit 10 and the image output unit 30.

  The image acquisition unit 10 includes a platen glass (original placement table) 11 made of transparent glass provided on a housing. The image acquisition unit 10 also has a light source 12 that emits light toward the surface (back surface) opposite to the document placement surface of the platen glass 11 below the platen glass 11, and the light emitted from the light source 12. A substantially concave reflecting shade 17 that reflects toward the glass 11 is provided. As the light source 12, a halogen lamp whose longitudinal direction is the direction of main scanning FS (Fast Scan) (the depth direction in the drawing) is used.

  Further, the image acquisition unit 10 receives reflected light from the platen glass 11 side and receives an image in the direction of the main scanning FS substantially perpendicular to the direction of the sub-scanning SS (Slow Scan) (the reading direction of the arrow X1 in the figure). A contact optical system including a light receiving unit 13 that sequentially outputs image signals (analog electrical signals) corresponding to reading and density, and a signal processing unit 14 that amplifies and outputs the image signals from the light receiving unit 13 to a predetermined level. Is. For example, the light receiving unit 13 includes a line sensor (not shown) including a photoelectric conversion element such as a CCD (Charge Coupled Device). The light receiving unit 13 is disposed on the substrate 15 together with the signal processing unit 14 and the like, and constitutes an optical scanning system (sensor unit) 16.

  Although not shown, the image acquisition unit 10 also includes a drive motor such as a wire, a drive pulley, or a stepping motor for moving the light source 12, the light receiving unit 13, the signal processing unit 14, and the like under the platen glass 11. Provided in the body. The driving pulley is reciprocally rotated by the driving force of the driving motor, and the wire is wound around the driving pulley by the rotation driving. As a result, the light receiving unit 13 and the like are configured to be able to reciprocate integrally below the platen glass 11 in the sub-scanning SS direction (arrow X1 in the figure) and in the opposite direction (arrow X2 in the figure). .

  In the above configuration, in the fixed reading method in which the original is read while being placed on the platen glass 11, the original is placed on the platen glass 11 serving as a document placing table by hand (a document feeder may be used) With the original fixed (stop-locked) at an arbitrary position on the platen glass 11, the light receiving unit 13 is moved and scanned at a constant speed in the direction of the arrow X1 (sub-scanning direction) from a predetermined reading start position. To expose and read the image.

  The image acquisition unit 10 converts an input image obtained by reading a document placed on the platen glass 11 into digital image data R, G, and B of red, green, and blue color components. For example, the light from the light source 12 irradiates a document placed on the platen glass 11, and the opposite light is split into red, green, and blue colors via an optical system (not shown). Each color light is incident on a light receiving unit 13 including a CCD line sensor or the like divided for each color light, and an input image is read at a resolution of, for example, 400 dpi (400 dots / 1 inch), whereby red (R), Analog image signals of green (G) and blue (B) color components are obtained.

  The signal processing unit 14 functioning as a pre (Pre) image processing unit amplifies the red, green, and blue image signals from the light receiving unit 13 to a predetermined level by an amplification unit (not shown), and performs, for example, shading correction. Pre-image processing is performed, and further, digital image data R, G, and B of red, green, and blue are output from the A / D converter by being converted into digital data by an A / D converter (not shown). The red, green, and blue image data R, G, and B are sent to the image processing unit 20 through the cable 19.

  The image output unit 30 has a tandem configuration having image forming units (transfer units / printing engines) 31 of output colors Y, M, C, and K arranged in parallel in a certain direction at regular intervals. In the following, each of the image forming units 31 of each color is denoted by reference symbols Y, M, C, and K, and the color symbols are omitted when collectively referred to. The same applies to other members.

  In the illustrated example, four output colors Y, M, C, and K are used. However, the present invention is not limited to this. For example, more outputs such as gray (gray) Gy as the fifth color are used. It may include a color or may be three colors of Y, M, and C excluding black (K). Even in these cases, the Y color with low human visual sensitivity is set as the first color (the color that is first output to the paper). Further, the combination of output colors is not limited to the Y, M, C (which may further include K) system, but may be, for example, the R, G, B system. Even in these cases, a color having low human visual sensitivity is set as the first color.

  A photosensitive drum 32 is disposed at the center of the image forming unit 31, and a primary charger 33, a developing unit 34, a transfer charger 35, and the like are disposed around the photosensitive drum 32. A writing scanning optical system such as a polygon mirror 39 for recording a latent image on the photosensitive drum 32 based on the formation data is provided.

  The image output unit 30 includes a paper cassette 41 and a conveyance path 42 for conveying the printing paper to the image forming unit 31. A leading edge detector 44 is provided in proximity to a conveyance path 42 for printing paper conveyed from the paper cassette 41 to each image forming unit 31. The leading edge detector 44 optically detects, for example, the leading edge of the printing paper fed onto the transfer belt (conveyance belt) 43 through the registration roller 42 a to obtain a leading edge detection signal, and this leading edge detection signal is sent to the image processing unit 20. send.

  The image processing unit 20 that functions as a post image processing unit synchronizes with the tip detection signal input from the image output unit 30, and displays red, green, and blue images from the signal processing unit 14 of the image acquisition unit 10. After predetermined image processing is performed on the data R, G, and B, Y, M, C, and K image formation data (for example, on / off binarized toner signal) is obtained, and the processed Y, M, C, and K are processed. Are sequentially input to the image output unit 30 at regular intervals (so-called tandem gap).

  In the image output unit 30, first, the semiconductor laser 38Y as a light source for forming a latent image is driven by yellow (Y) image formation data from the image processing unit 20, thereby converting the yellow image formation data into an optical signal. The converted laser beam is irradiated toward the polygon mirror 39. The laser light further scans the photosensitive drum 32Y charged by the primary charger 33Y via the reflection mirrors 47Y, 48Y, and 49Y, thereby forming an electrostatic latent image on the photosensitive drum 32Y. The electrostatic latent image is converted into a toner image by a developing device 34Y to which yellow toner is supplied. The toner image is transferred to a sheet by a transfer charger 35Y while the sheet on the transfer belt 43 passes through the photosensitive drum 32Y. Transcribed above. After the transfer, excess toner is removed from the photosensitive drum 32Y by the cleaner 36Y.

  Similarly, the semiconductor lasers 38M, 38C, and 38K are driven by the corresponding M, C, and K color image formation data obtained from the image processing unit 20 sequentially with respect to the yellow image formation data at regular intervals. As a result, the image forming data of each color is converted into an optical signal, and the converted laser light is irradiated toward the polygon mirror 39. The laser light is further scanned on the photosensitive drums 32M, 32C, and 32K charged by the primary chargers 33M, 33C, and 33K via the reflection mirrors 47M to 49M, 47C to 49C, and 47K to 49K, thereby exposing the photosensitive drums. Electrostatic latent images are sequentially formed on the body drums 32M, 32C, and 32K.

  Each electrostatic latent image is sequentially converted into a toner image by developing units 34M, 34C, and 34K to which toner of each color is supplied, and each toner image is a photosensitive drum 32M, 32C, and 32K to which the paper on the transfer belt 43 corresponds. Are sequentially transferred onto the paper by the corresponding transfer chargers 35M, 35C, and 35K.

The paper on which the toner images of each color of Y, M, C, and K are sequentially transferred in this way is peeled off from the transfer belt 43, the toner is fixed by the fixing roller 45, and is discharged outside the copying machine. .
Note that the configuration of the image output unit 30 is not limited to that described above, and may be, for example, an intermediate transfer type including one or two intermediate transfer belts.

  FIG. 2 is a block diagram of an embodiment of an image processing unit 20 that functions as a main image processing apparatus provided in the color copying apparatus 1 having the above configuration. In the image processing unit 20, red, green, and blue image data R, G, and B are input from the image acquisition unit 10 (signal processing unit 14). Alternatively, the image data L is converted into image data L, a, and b in a Lab color space (correctly L * a * b *) which is a device-independent color space by a pre-stage color conversion unit (not shown). , A, b are input. In the following description, it is assumed that the image data L, a, and b are input to the image processing unit 20.

  As shown in the figure, the image processing unit 20 is roughly divided into a front image processing unit 20a, a rear image processing unit 20b, and a peripheral unit 20c. As the peripheral unit 20c of the present embodiment, a data IF (Interface) unit 800 having a path switching unit 801 is provided.

  A path switching unit 801 is a front-stage switching unit 801a that is an example of a processing target image input unit provided on the left side in the figure, an intermediate switching unit 801b provided in the center part in the figure, and a processed image provided on the right side in the figure. It comprises a rear-stage switching unit 801c, which is an example of an output unit, and a connection unit 801d that connects them. The pre-stage image processing unit 20a and the post-stage image processing unit 20b are divided by an intermediate switching unit 801b extending from above in the center of the path switching unit 801 in the drawing.

  Each functional unit of the path switching unit 801 has a bidirectional data function and a pipeline processing function for switching input / output data of an image processing path, so that a plurality of data input from any of the image processing blocks can be performed. Then, a switching process to make output data to the corresponding subsequent block is performed. For example, the 8-bit image data captured by the upstream switching unit 801a is directly used as the upstream image processing unit 20a, the 8-bit image data captured by the intermediate switching unit 801b is directly processed by the downstream image processing unit 20b, and the downstream switching unit 801c. It is also possible to pass the 8-bit image data fetched to the image output unit 30 as it is.

  It is also possible to send the 8-bit image data captured by the intermediate switching unit 801b to the subsequent-stage switching unit 801c as it is via the connection unit 801d and to pass it to the image output unit 30 side. It is also possible to pass the 8-bit image data captured by the subsequent-stage switching unit 801c to the intermediate switching unit 801b or the previous-stage switching unit 801a via the connection unit 801d. It is also possible to send 10-bit image data captured by the upstream switching unit 801a to the downstream switching unit 801c as it is via the connection unit 801d and pass it to the image output unit 30 side.

  Further, by inputting / outputting 8-bit image data in the lower part of the intermediate switching unit 801b in the drawing, it is possible to bypass the image path and perform desired processing outside the image processing unit 20. For example, processing for improving image quality by performing desired image processing using image data of the entire page (for example, ground color removal processing and density adjustment processing), and a certain interval in order to correspond to the tandem gap. When executing a tandem gap correction function using a page memory for passing image data to the image output unit 30 or a page rearrangement function (so-called electronic sort), the image data Lab is transferred from the intermediate switching unit 801b to the page memory. (An example of an image memory; a semiconductor memory or a storage medium such as a hard disk device) may be provided to a sub-image processing device (hereinafter referred to as a page memory processing device) 910, and processed image data Lab is transferred to the intermediate switching unit. It performs the function of receiving at 801b. Further, after the page memory processing device converts the data into YMCK color space data and performs desired image processing on the YMCK color space (may be similar to the image processing of the subsequent image processing unit 20b), the intermediate switching unit It is also possible to transfer the 8-bit image data captured in 801b and the intermediate switching unit 801b to the subsequent-stage switching unit 801c as it is via the connection unit 801d and pass it to the image output unit 30 side.

  In these cases, in order to reduce the memory capacity, the image data is compressed and stored in the page memory, and then the image compression memory function for decoding the read image data is used. Further, image data Lab corresponding to each of the output colors YMCK is sequentially taken into the intermediate switching unit 801b from the page memory processing device 910 which is an example of the image storage processing device with a delay of a certain interval corresponding to the tandem gap. It may be.

  The pre-stage image processing unit 20 a includes a ground color detection unit 102. The post-stage image processing unit 20 b includes a pre-stage color adjustment unit 400, a color conversion unit 500 that converts an input color signal into another color signal system, and a post-stage color adjustment unit 600 having a ground color removal processing unit 608.

  Although not shown, the preceding-stage color adjustment unit 400 includes a preceding-stage background color removal processing unit that executes a background color removal processing function that is an example of the AE function. Similarly, the post-stage color conversion unit 600 includes a post-stage background color removal processing unit that executes a background color removal process function. The rear-stage background color removal processing unit has the same function as the front-stage background color removal processing unit.

  Here, in the configuration of the present embodiment, the area from the front stage color adjustment unit 400 to the rear stage color adjustment unit 600 includes a processing block for color images and a processing block for monochrome images. Regardless of whether the document read by the unit 10 is a color document or a monochrome document (typically a monochrome document), the respective processing blocks are processed in parallel. This is to prevent the productivity from being lowered even if the image output unit and the pre-scanless ACS have a tandem configuration by adopting a configuration in which color image processing and monochrome image processing are performed in parallel. Note that the image processing method for achieving pre-scanless ACS may use the same method as in Patent Documents 2 and 3 (preferably Patent Document 3). In the configuration of the present embodiment, two systems for monochrome (LL0, LL1) are provided. In each of the systems LL0 and LL1, ground color removal processing is performed at different ground color removal levels.

  In addition, the pre-stage color adjustment unit 400 and the post-stage color conversion unit 600 are provided with a plurality of functional blocks that perform ground color removal processing.

  Hereinafter, the outline of each functional part constituting the image processing unit 20 will be described, and the image compression memory function which is a characteristic part of the present embodiment will be described in detail later. In the following description, “D” indicating that the image data is image data, a reference code of the functional part, and a reference code of each color information are sequentially attached to the image data output from each functional part. Will be shown. In addition, when the plurality of color signals are collectively referred to, “D” indicating image data, a functional part reference code, and all color information reference codes are sequentially attached. . For example, the brightness data L output from the image acquisition unit 10 is D10L, the chromaticity data a and b are D10a and D10b, and these are collectively D10Lab.

  In the pre-stage image processing unit 20a, the ground color detection unit 102 detects the ground color component (background level) of the document to be read based on the brightness data D10L and the color data D10a and D10b input from the image acquisition unit 10, and performs color processing. According to each of the original and the monochrome original, ground color image data indicating the ground color component is separately output. The ground color detection unit 102 is configured to be able to switch between various methods as a ground color component detection method. For example, real-time AE background detection, histogram AE background detection, and the like.

  For real-time AE, reference may be made to, for example, JP-A-6-46255, JP-A-7-322069, JP-A-7-264408, JP-A-6-311359, and JP-A-6-311364. Regarding the histogram AE background detection, refer to Japanese Patent Laid-Open No. 4-0372 and Japanese Patent No. 3134292.

  The ground color detection unit 102 according to the present embodiment uses the detection lightness signal D801L1 and the image path lightness input via the path switching unit 801 regardless of which detection method such as real-time AE background detection or histogram AE background detection is used. One of the signals D801L2 is selected as detection input data relating to brightness.

  The ground color detection unit 102 detects the background color using the color signals D801a and D801b input from the image acquisition unit 10 via the upstream switching unit 801a of the path switching unit 801.

  Further, when the histogram AE background detection is employed, the ground color detection unit 102 is configured to be able to switch to another detection method in real time when the detection data is obtained.

  Here, when the ground color detection unit 102 detects the ground color component (background level) of the document to be read in line units, the color image data YMCK path for the color document is subjected to detection processing suitable for the color image. The background color image data DAEC is output separately for the monochrome image data LL path for a monochrome document, and the background color image data DAELL subjected to processing suitable for a monochrome image is output separately.

  The pre-stage ground color removal processing unit calculates the ground color component of the document by calculation on the image data Lab in the device-independent color space based on the ground color component (ground color image data) detected by the ground color detection unit 102. Remove. For example, image data having a predetermined background density or less is cut out of the image data D801Lab input from the intermediate switching unit 801b corresponding to each of the color image data Y, M, C, K and the monochrome image data LL ( The background removal process to be invalidated is performed, and the processed data Lab corresponding to each of the color image data Y, M, C, K and the monochrome image data LL is passed to the subsequent processing circuit.

  This pre-stage ground color removal processing unit has a ground level fixing mode in which the ground level is removed at the ground level captured by the first line, a ground level variable mode (real-time line-by-line removal) mode in which the ground level is fetched for each line and ground removal is performed One of the register fixed setting modes for taking in the value set in the register and performing background removal can be set.

  When the image compression memory function, which is a characteristic part of the present embodiment, is executed, the intermediate switching unit 801b is transferred to the page memory processing device 910 at the lower part in the figure, and the processed image data Lab is transferred to the intermediate switching unit. Receive at 801b.

  In the pre-stage color adjustment unit 400, the image data Lab input for each of the color image data YMCK and the monochrome image data LL (LL0, LL1) is subjected to ground color removal processing, and then processed for the color image data YMCK and Image data Lab for monochrome image data LL is input to the color conversion unit 500.

  A color conversion unit 500 provided at the subsequent stage of the previous color adjustment unit 400 performs color conversion of the brightness data D400L and the color data D400a and D400b into output image data Y, M, C, and K (D500YMCK).

  In the post-stage color conversion unit 600, similarly to the pre-stage color adjustment unit 400, ground color removal processing is performed for each of the color image data YMCK and the monochrome image data LL (LL0, LL1).

  As can be seen from the description of the above configuration, the image processing unit 20 of the present embodiment is configured to include a plurality of functional units in charge of processing to reduce the ground color component. In addition, although the illustrated example has a configuration including two stages of ground color removal processing units, a configuration including three or more stages may be used.

  With such a configuration, it is possible to adjust the processing parameters at each stage according to the image processing characteristics, and it becomes easy to design an image quality according to the characteristics of the image processing. Thereby, even when the document mode is designated, a preferable image can be obtained by performing the ground color removal processing at an appropriate place.

  FIG. 3 is a diagram for explaining a page memory processing device 910 having an image compression / decompression processing function used for realizing the image compression memory function in the image processing unit 20 shown in FIG. Here, FIG. 3A is a block diagram showing a configuration example of the page memory processing device 910, and FIG. 3B shows image data LabY corresponding to each of the output colors YMCK output from the page memory processing device 910. FIG. 6 is a diagram illustrating an example of output timing of LabM, LabM, LabC, and LabK.

  A page memory processing device 910 that performs image compression / decompression processing is used for, for example, electronic sorting. At this time, the page memory processing device 910 compresses image data in units of pages in a compressed image format such as JPEG or PNG, and an image including a hard disk device (HDD) that is an example of a semiconductor memory or a nonvolatile storage medium. The memory unit 914 has a function of temporarily storing (compressed and saved) or decompressing a compressed and saved print image (page unit image data).

  Specifically, as illustrated in FIG. 3A, the page memory processing device 910 includes an encoding unit 912 that is an example of a compression processing unit, an image memory unit 914 that is an example of an image storage unit, and an expansion processing unit. An example includes a decoding unit 916 and an output unit 918. The encoding unit 912 includes encoding units 912L, 912a, and 912b corresponding to the components of the input image data Lab. The image memory unit 914 includes image memory units 914L, 914a, and 914b corresponding to the components of the input image data Lab. Similarly, the decoding unit 916 includes decoding units 916L, 916a, and 916b corresponding to the components of the input image data Lab. On the other hand, the output unit 918 outputs the input image data Lab so as to correspond to each of the output colors YMCK, and outputs 918Y, 918M, 918C, 918K corresponding to the respective components of the image data YMCK. Have That is, each function unit of the page memory processing device 910 has an individual processing function unit for each input component and output component.

  As shown in FIG. 3B, in correspondence with the image output unit 30 having the tandem structure, the page memory processing device 910 has an image from the image memory unit 914 with a delay of a constant interval corresponding to the tandem gap. Read the data Lab. For example, after starting the reading of the Y-color image data LabY as the first color, the M-color image data LabM is read out after a tandem gap Tym between the Y color and the M color as the second color. In addition, after starting the reading of the M-color image data LabM as the second color, the C-color image data LabC is read out after a tandem gap Tmc between the M color and the third color C. Finally, after the start of reading the C color image data LabC as the third color, the K color image data LabK is read out after a tandem gap Tck between the C color and the K color as the fourth color. Accordingly, the image data LabY, LabM, LabC, and LabK corresponding to each of the output colors YMCK are output from the page memory processing device 910 to the image processing unit 20 side with a delay of a constant interval corresponding to the tandem gap. To. This function is called a tandem gap correction function.

  As described above, when the tandem gap correction function is operated in the page memory processing device 910, depending on the tandem gap length, the output unit 918 in the page memory processing device 910 and each functional part of the subsequent image processing unit 20b For example, there may be a case where different pages are processed for the first color and other colors. In this case, the processing parameters set in the processing function unit of each component are different, and the control becomes complicated and complicated as it is. Although omitted from the description, the page memory processing device 910 of the present embodiment also has a function of solving this problem.

  Although not shown, the page memory processing device 910 reads data from a parameter setting unit that sets compression / decoding parameters, a write control unit that controls data writing to the image memory unit 914, and an image memory unit 914. A read control unit for controlling the above.

  For example, the parameter setting unit determines a compression parameter for encoding in the encoding unit 912. Next, the parameter setting unit inputs the determined encoding parameter for each image component to the corresponding image component encoding unit 912 and decoding unit 916.

  The encoding unit 912 uses, for example, orthogonal transform encoding such as DCT (Discrete Cosine Transform) or vector quantization for the image data Lab captured from the intermediate switching unit 801b of the image processing unit 20 using the set encoding parameters. The encoded image data L, a, and b are generated by encoding and compression processing (either irreversible compression or lossless compression may be used). Thereafter, the writing control unit corresponds to the encoded image data of each component L, a, b of the input image compressed by the encoding unit 912 in the image memory unit 914 which is an example of the image storage unit. Write at approximately the same time.

  Next, in synchronization with a leading edge detection signal (a signal indicating a printing start point in the sub-scanning direction) from a leading edge detector (not shown) of the image output unit 30, the reading control unit reads each component L, a of the input image from the image memory unit 914. , B are sequentially read at regular intervals (YMCK delay) so as to absorb the tandem gap and input to the decoding unit 916. The decoding unit 916 outputs the encoded image data of the input components L, a, and b for the output colors Y, M, C, and K sequentially read from the image memory unit 914 at regular intervals by the parameter setting unit. Using the set encoding parameter, decoding (decompression processing) corresponding to encoding in the encoding unit 912 is performed to return to the original image data (decoded data), and the output colors Y, M, C, The decoded data L, a, and b for K are set as a set and input to the corresponding ones in the output unit 918.

  In the above description, all the output colors Y, M, C, and K are encoded by a predetermined format method and irreversibly compressed, and then stored in the image memory unit 914. Not limited to the method, the image data Lab input without compression for a predetermined output color may be stored in the image memory unit 914 as it is. In this case, the image data Lab is stored in the image memory unit 914 without being compressed and the image data read from the image memory unit 914 is transferred to the output unit 918 without being decoded. And a normal processing system for decoding the image data read from the image memory unit 914 and passing it to the output unit 918 (an image compression memory function of a second example described later) See).

  FIG. 4 is a diagram illustrating a first example of an image compression memory function realized by the above-described page memory processing device 910 and the image processing unit 20 acting in cooperation. Here, FIG. 4A is a diagram showing an example of the relationship between tandem gap timing and print processing for each output color, and FIG. 4B is a block diagram showing a configuration example related to the image compression memory function. . In FIG. 4B, only the YMCK system, which is a signal system for color originals, is shown, and illustration of LL0 and LL1 for monochrome originals is omitted.

  As shown in FIG. 4 (A), the image compression memory function of the first example uses the invisible Y color with low human visual sensitivity as the first color, and the first color (Y) is effectively an image. The first through print in which the image data is not put in the memory unit 914, and thus the image processing using the page memory processing device 910 is not performed (that is, the image processing outside the image processing unit 20 is omitted). While executing the processing, image processing using the page memory processing device 910 is performed for the second color (M), the third color (C), and the fourth color (K) other than the first color (Y). This is characterized in that a normal print process via the network is performed. This will be specifically described below.

  As shown in FIG. 4B, the color copying apparatus 1 that executes the image compression memory function of the first example is a page memory process in which an image taken into the image processing unit 20 is temporarily provided outside the image processing unit 20. By passing to the device 910, the image path is bypassed, the page memory processing device 910 outside the image processing unit 20 performs a desired process, and the processed image is taken back into the image processing unit 20 to obtain the final result. Passing to the image output unit 30 after processing (that is, returning to the original image path) is referred to as “normal processing”.

  At this time, the image data Lab input from the image acquisition unit 10 and subjected to a predetermined process such as a scaling process in a preceding image processing unit 20a (not shown) is paged via the intermediate switching unit 801b of the image processing unit 20. Although it is input to the memory processing device 910, the post-stage image processing unit 20b does not use the processed data LabY by the output unit 918 corresponding to the inconspicuous Y color with low human visual sensitivity among the output colors YMCK. The system of the image data Lab input from 10 is used as it is as the image data LabY to be processed. That is, the process of detouring (switching) the image path is omitted. On the other hand, for the second color (M), the third color (C), and the fourth color (K) other than the first color (Y), processed data on which image processing using the output unit 918 has been performed. LabM, LabC, and LabK are taken into the subsequent image processing unit 20b via the intermediate switching unit 801b.

  At this time, the image data Lab input from the image acquisition unit 10 is used as it is as the image data LabY to be processed as it is, and the output color with a delay of a constant interval corresponding to the tandem gap is used. Image processing units of image data D910LabM, D910LabC, and D910LabK corresponding to each of the output colors MCK so that data D600M, D600C, and D600K corresponding to each of YMCK are output from image processing unit 20 to image output unit 30. The tandem gap absorption function is realized by adjusting the input timing to the 20 side.

  In the image processing unit 20, for the Y color, the ground color removal processing, contrast adjustment (density adjustment), and hue adjustment are performed on the image data LabY input from the image acquisition unit 10 by the pre-stage color adjustment unit 400. Are applied in a predetermined order, and the color conversion unit 500 performs color conversion processing to generate image data D500Y for Y color. Then, the Y color image data D500Y is subjected to filter processing by the filter processing unit 300 (in the case of a configuration arranged on the subsequent image processing unit 20b side), and the subsequent color conversion unit 600 performs background color processing. Removal processing, contrast adjustment (density adjustment), hue adjustment, and gradation correction processing are performed in a predetermined order to obtain data D600Y, and this data D600Y is transferred to the image output unit 30. On the other hand, for M color, C color, and K color, image data LabM, LabC, and LabK input from the page memory processing device 910 are processed in the same manner as for Y color, and data D600M, D600C and D600K are transferred to the image output unit 30.

  According to the configuration of the first example as described above, the first through-print process for the Y color that does not pass through the page memory processing device 910 causes the image forming unit (engine) 31Y for the Y color that is the first color to The image processing can be executed by absorbing the tandem gap Tym with the image forming unit (engine) 31M for the M color that is the second color. As a result, the image processing of the entire color copying apparatus 1 can be completed quickly, and the first output product (for example, a copy) is discharged after the output command is issued (for example, after the start button is pressed). The processing time FCOT up to can be shortened.

  Note that the image processing performed on the image processing unit 20 side can perform the same processing for all of the Y color, M color, C color, and K color, as in the configuration to which the present embodiment is not applied. For example, the image processing unit 20 can execute ground color removal processing by real-time AE background detection for all of Y color, M color, C color, and K color.

  However, since the Y color is a low-visibility color with low human visual sensitivity, the output image printed out by the image output unit 30 is almost in terms of image quality without performing image processing for improving the image quality. There is no inconvenience, and the image quality improvement effect that is practically inconvenient can be obtained by performing image processing for improving the image quality only for the M, C, and K colors. That is, high-speed processing is possible while maintaining the image quality at the same level as the conventional one.

  FIG. 5 is a diagram illustrating a second example of an image compression memory function realized by the above-described page memory processing device 910 and the image processing unit 20 acting in cooperation. Here, FIG. 5A is a diagram showing an example of the relationship between tandem gap timing and print processing for each output color, and FIG. 5B is a block diagram showing a configuration example related to the image compression memory function. .

  In the image compression memory function of the second example, as shown in FIG. 5A, the invisible Y color with low human visual sensitivity is set as the first color, and image compression is omitted for the first color (Y). (Of course, the corresponding decoding process is also omitted) and the image data is stored in the image memory unit 914, and the second through print process is also performed for the Y color via the image process using the page memory processing device 910. On the other hand, for the second color (M), third color (C), and fourth color (K) other than the first color (Y), image compression is performed as usual and image data is stored in the image memory unit 914. And a normal print process via image processing using the page memory processing device 910 is performed. Hereinafter, the difference from the first example will be specifically described.

  As shown in FIG. 5B, the color copying apparatus 1 that executes the image compression memory function of the second example performs image processing using the page memory processing device 910 even for the inconspicuous Y color with low human visual sensitivity. The processed data LabM, LabC, and LabK that have been subjected to are taken into the image processing unit 20 via the intermediate switching unit 801b. However, in the page memory processing device 910, the image data Lab input without being compressed for the Y color is stored in the image memory unit 914 as it is, and the image data Lab read from the image memory unit 914 is decoded (decompressed). The data is input to the output unit 918 without processing.

  FIG. 6 is a block diagram showing a configuration example of a page memory processing device 910 having an image compression / decompression processing function used for realizing the image compression memory function of the second example.

  As shown in FIG. 6, the page memory processing device 910 stores the image data Lab in the image memory unit 914 without compressing it, and also outputs the image data read from the image memory unit 914 to the output unit 918 without decoding it. The processing system for Y color to be transferred and the image data Lab are compressed and stored in the image memory unit 914, and the image data read from the image memory unit 914 is decoded and passed to the output unit 918. The color processing system is different from that shown in FIG.

  Specifically, the image memory unit 914 includes image memory units 914L1, 914a1, and 914b1 that store uncompressed image data Lab corresponding to respective components of the input image data Lab. 914Y and an image memory unit 914MCK having image memory units 914L2, 914a1, and 914b2 for storing image data Lab subjected to compression processing corresponding to each component of the input image data Lab. The encoding unit 912 and decoding unit 916 pass only the image data Lab for M color, C color, and K color.

  According to the configuration of the second example as described above, the Y color image forming unit 31Y and the M color image forming unit 31M are equivalent to the second through print processing in which the Y color is not passed through the compression / decompression processing. Image processing can be executed by absorbing the tandem gap Tym between the first and second sheets, whereby the image processing of the entire color copying apparatus 1 can be completed quickly, and the first sheet after the output command is issued. The processing time FCOT until the output product is discharged can be shortened.

  FIG. 7 is a diagram illustrating a third example of an image compression memory function realized by the page memory processing device 910 and the image processing unit 20 working together. Here, FIG. 7A is a diagram showing an example of the relationship between the tandem gap timing and the ground color detection processing and ground color removal processing for each output color, and FIG. 7B is a configuration example related to the image compression memory function. It is the block diagram which showed.

  In the image compression memory function of the third example, as shown in FIG. 7A, the inconspicuous Y color with low human visual sensitivity is set as the first color, and real-time AE background detection is performed for the first color (Y). It is possible to acquire ground color information (background information) such as high-speed and perform ground color removal processing by ground color detection processing excellent in immediacy, and other second colors (except for the first color (Y)) ( For M), the third color (C), and the fourth color (K), a fixed value of ground color information (background information) with high accuracy that is low speed (takes time to acquire) such as histogram AE background detection is used. It is characterized in that a ground color removal process is performed by the ground color detection process. This will be specifically described below.

  As shown in FIG. 7B, in the configuration of the third example, similarly to the configuration of the second example, an image using the page memory processing device 910 is also used for the inconspicuous Y color with low human visual sensitivity. The processed data LabM, LabC, and LabK that have been processed are taken into the image processing unit 20 via the intermediate switching unit 801b.

  In the page memory processing device 910, the input image data Lab for Y color is also compressed and stored in the image memory unit 914, and decoding processing (decompression processing) is performed on the image data Lab read from the image memory unit 914. And input to the output unit 918. As in the second example, the image data Lab input without being compressed for the Y color is stored in the image memory unit 914 as it is, and the image data Lab read from the image memory unit 914 is decoded (decompressed). It is good also as a structure input into the output part 918, without performing a process.

  Regarding the ground color removal processing, the image processing unit 20 executes ground color removal processing by real-time AE background detection for the Y color, and for the M color, C color, and K color other than the Y color, AE detection using a definite value. As a component for executing the ground color removal processing by the processing (specifically, the histogram AE background detection), the configuration of the ground color detection unit 102 is different from the configurations of the first and second examples.

  Specifically, since the processing that emphasizes ground color detection performance and ground color removal performance is called “normal processing”, ground color information that takes time to acquire ground color information but can detect ground color information with high accuracy. Executing the removal process as a “normal process” is applied to the output color components that have a relatively large image quality influence (all except the output color components that have less image quality influence), while the image quality is relatively For output color components that are less affected by the background color, processing based on ground color detection processing that is superior in immediacy is executed in order to perform processing that places importance on ground color detection speed. For this reason, the ground color detection unit 102 of the third example includes a ground color detection unit 102R that detects the ground color component of the document by a real-time AE background detection method that is an example of ground color detection processing excellent in immediacy, and accuracy. A ground color detection unit 102H that detects a ground color component of a document by a histogram AE background detection method that is an example of processing capable of detecting high ground color information.

  When the image data Lab is input from the image acquisition unit 10 to the image processing unit 20, the ground color detection unit 102 </ b> R is based on the ground color component (ground color image) of the input image based on the image data Lab input from the image acquisition unit 10. Data DAECR) is detected in real time. At this time, the image processing unit 20 subjects the image data Lab input from the image acquisition unit 10 to a scaling process or the like in the previous image processing unit 20a and passes it to the page memory processing device 910. Stored in the memory unit 914.

  For example, in real-time AE background detection, a histogram of background density distribution of a document is created based on pixel data for background detection (the number of which sequentially increases) obtained after reading is started, and the frequency of the histogram is calculated. The background removal threshold value TL is determined as the ground color image data DAECR based on the first density area exceeding the predetermined frequency, as examined from the high density side. At this time, ground color information (density information) is first detected for each line, and the background removal threshold TL is converged based on the ground color information for each line.

  The ground color detection unit 102H has a page memory (not shown) for storing image data for one page, temporarily stores the image data Lab acquired from the image acquisition unit 10 in the page memory, and then stores all image data for one page. Is read (asynchronously and at high speed with the reading of the image memory unit 914 of the page memory processing device 910) and the histogram analysis is performed to detect the final value of the ground color component (ground color image data DAECH) of the document. When storing data in the page memory, a configuration that performs compression / decompression processing as in the page memory processing device 910 may be employed. In addition to storing pixel data for each pixel, for example, ground color information (density information) for each line detected by the ground color detection unit 102R is stored, and background information for each line is subjected to histogram analysis. By doing so, the final value of the ground color component of the document (ground color image data DAECH) may be detected.

  The ground color image data DAECR obtained by the ground color detection unit 102R by the real-time AE background detection method is input to the Y system function unit of the front color adjustment unit 400 and the Y system function unit of the back color conversion unit 600. The Y system function unit executes ground color removal processing by real-time AE background detection.

  On the other hand, the ground color image data DAECH (the determined value of the ground) obtained by the histogram AE background detection method by the ground color detection unit 102H is the M system function unit, the C system function unit, and the K system function of the preceding color adjustment unit 400. And the M-system function unit, the C-system function unit, and the K-system function unit of the subsequent color conversion unit 600. The M-system function unit, the C-system function unit, and the K-system function unit are represented by the histogram AE. Executes ground color removal processing based on background detection.

  FIG. 8 is a diagram for explaining the effect of the image compression memory function of the third example. As shown in FIG. 8A, when the ground color removal process by the histogram AE background detection is executed for all output colors including the Y color, the histogram analysis is performed after storing all the image data for one page, If the final value (ground color image data) of the color image data is not obtained, the processed image data LabY is read from the page memory processing device 910, and then the background color removal process is started in the stage image processing unit 20b. Can not do it.

  On the other hand, according to the configuration of the third example, as shown in FIG. 8B, for the Y color, ground color removal processing by real-time AE background detection is executed, and the M color, C color, Since the ground color removal process by the histogram AE background detection is executed for the K color, the Y color image data LabY is read from the page memory processing device 910 before the final value of the ground color image data is obtained. (Hereinafter referred to as advance reading).

  Here, the degree of pre-reading is defined by the tandem gap Tym between the Y color as the first color and the M color as the second color. That is, when the ground color removal processing is started for the M color that is read by Tym later than the Y color, the fact that the definite value DAECH of the ground color image data is obtained indicates that the Y before the definite value is obtained. This is the limit for reading the color image data LabY.

  According to the configuration of the third example as described above, image formation for Y color is performed by the amount that the image data LabY for Y color is read in advance from the page memory processing device 910 before the final value of the ground color image data is obtained. The ground color removal processing can be executed by absorbing the tandem gap Tym between the portion 31Y and the image forming portion 31M for M color, so that the image processing of the entire color copying apparatus 1 can be completed quickly. As a result, the processing time FCOT from when the output command is issued until the first output product is discharged can be shortened.

  Here, when the ground color removal processing by real-time AE background detection is compared with the ground color removal processing by histogram AE background detection, the ground color removal processing by histogram AE background detection is more accurate. This is because the ground color image data obtained by the real-time AE background detection is not stable until a while after the start of the detection process.

  For example, in real-time AE background detection, a histogram of background density distribution of a document is created based on pixel data for background detection (the number of which sequentially increases) obtained after reading is started, and the frequency of the histogram is calculated. The background removal threshold value TL is determined as the ground color image data based on the first density area exceeding the predetermined frequency, as examined from the high density side. At this time, ground color information (density information) is first detected for each line, and the background removal threshold TL is converged based on the ground color information for each line.

  Here, in the case of a document in which an image is recorded to almost the entire line, as shown in FIG. 8C, the pixel data for background detection (for example, brightness information L) varies. For example, if there is a black image in almost the entire line, the density of this black image is determined as pixel data for background detection. For a line having no image, the background density of the document is determined as pixel data for background detection. Further, if an image (white image) whose density is lower than the background density of the document is present in the entire line, the density of the light image is determined as background detection pixel data. For this reason, for example, in the case of a document on which an image has been recorded up to the leading edge of the document, since it is affected by variations in pixel data for background detection, the detected background removal threshold TL is not necessarily the background removal immediately after the start of reading. It will not be suitable for. That is, the ground color removal performance is inferior.

  On the other hand, as reading progresses and the number of background detection pixel data increases sequentially, the number of lines without an image gradually increases, and the influence of lines with black and white images is alleviated. Therefore, in the case of a document in which an image is recorded up to the front end of the document, the background removal threshold TL (that is, ground color image data) is converged as reading progresses. Near the completion of reading of the entire original, the ground color image data is in a stable state.

  Accordingly, the ground color removal performance for the Y color is inferior to the ground color removal performance for the other M, C, and K colors. However, since the Y color is a low-visibility color with low human visual sensitivity, the output image printed out by the image output unit 30 is superior in image quality even if the ground color removal processing by the real-time AE background detection is used. There is almost no inconvenience, and a ground color removal effect that is practically inconvenient can be obtained by performing ground color removal processing by histogram AE background detection only for the M, C, and K colors.

  In the above description, the ground color detection unit 102R starts a process of detecting the ground color component (ground color image data) of the input image in real time based on the image data Lab input from the image acquisition unit 10. The color detection unit 102H performs the histogram analysis after holding the image data Lab input from the image acquisition unit 10 in a page memory (not shown), but is not limited to such a configuration. For example, as shown in the lower part of FIG. 8A, the ground color detection unit 102R may perform processing for detecting ground color image data in real time using the image data LabY output from the page memory processing device 910.

  For example, when page order is rearranged by the electronic sort function in the page memory processing device 910, the image at the time of reading is different from the image at the time of the actual printing process. In this aspect, the read image detected with the ground color is different from the target image for the ground color removal process, which causes inconvenience. In such a case, by adopting this modification, the ground color detection image and the ground color removal target image can be made common, and the inconvenience can be solved. In this case, the ground color detection unit 102H uses the image data for the target image of the ground color removal process among the images held in the page memory.

  FIG. 9 is a diagram illustrating a fourth example of the image compression memory function realized by the page memory processing device 910 and the image processing unit 20 acting in cooperation. Here, FIG. 9A is a block diagram showing a relationship between tandem gap timing and ground color detection processing and ground color removal processing for each output color, and FIG. 9B is a block diagram showing a configuration example related to the image compression memory function. is there.

  In the image compression memory function of the fourth example, as shown in FIG. 9A, the inconspicuous Y color with low human visual sensitivity is set as the first color, and the first color (Y) is first a real-time AE background. A feature is that ground color removal processing by detection is executed, and when a definite value such as histogram AE background detection is obtained, ground color removal processing by background detection is switched to ground color removal processing using a definite value. For the second color (M), the third color (C), and the fourth color (K) other than the first color (Y), as in the third example, a deterministic value such as histogram AE background detection is used. The ground color removal process is executed by the AE detection process using the. This will be specifically described below.

  As shown in FIG. 9B, the configuration of the fourth example is substantially the same as the configuration of the third example. The difference is that the ground color image data obtained by the histogram AE background detection method by the ground color detection unit 102H is also input to the Y system function unit of the front color adjustment unit 400 and the Y system function unit of the back color conversion unit 600. It is the point which is doing.

  In the image processing unit 20, when the background color removal process is performed on the Y color system, the Y system function unit of the front color adjustment unit 400 and the Y system function unit of the rear color conversion unit 600 are firstly real-timed by the ground color detection unit 102R. Based on the ground color image data obtained by the AE ground surface detection method, ground color removal processing by real-time AE ground surface detection is executed. Then, when the ground color image data obtained by the histogram AE background detection method is input by the ground color detection unit 102H, that is, when the final value of the ground color component by the histogram AE background detection is obtained, this ground color image is obtained. Switch to histogram AE ground color removal processing using data.

  According to the configuration of the fourth example, as in the third example, the image data LabY for the Y color is read in advance from the page memory processing device 910 before the final value of the ground color image data is obtained. The image processing of the color copying apparatus 1 as a whole can be completed quickly, and the processing time FCOT from when the output command is issued until the first output product is discharged can be shortened.

  In addition, since the ground color removal processing based on the real-time AE background detection is switched to the ground color removal processing using the confirmed value when the final value of the ground color image data is obtained, the ground color for the Y color is thereafter used. Since the removal performance is equivalent to the ground color removal performance of other M, C, and K colors, as a whole, the accuracy of the ground color removal processing is higher than that of the configuration of the third example.

  In the description of the first to fourth examples of the image compression memory function realized by the cooperation of the page memory processing device 910 and the image processing unit 20, the ground color removal processing shown in FIG. Although the example applied to what is provided in a plurality of stages (image processing unit 20 having the configuration shown in FIG. 2) is shown, the application range is not necessarily limited to the image processing unit 20 having the configuration shown in FIG. . For example, the present invention can be applied to the image processing unit 20 having only one stage or three or more stages of ground color removal processing functions.

  FIG. 10 is a block diagram showing an example in which the image compression memory function is applied to the image processing unit 20 having one stage of the ground color removal processing function. Here, FIG. 10A is a diagram showing a modified example of the first example shown in FIG. 4, and FIG. 10B is a diagram showing a modified example of the fourth example shown in FIG. In either case, the preceding color adjustment unit 400 is not provided, and the background color removal processing is performed by the subsequent color removal processing unit 602 in the subsequent color conversion unit 600.

  The configuration shown in FIG. 10A is the same as that of the first example, except that the ground color removal processing by the pre-stage color adjustment unit 400 is not performed on the first example shown in FIG. On the other hand, the configuration shown in FIG. 10B is different from the fourth example in the method of detecting the ground color image data (the determined value of the background) by the histogram AE background detection method. That is, instead of the ground color detection unit 102H of the fourth example shown in FIG. 9, a background detection processing device (CPU; Central Processing Unit) that detects ground color image data (a determined value of the background) by the histogram AE background detection method. ) 110 is provided outside the image processing unit 20.

  The background detection processing device 110 includes a memory (not shown), and temporarily stores ground color information (density information) for each line detected by the ground color detection unit 102 in the memory, and then stores the ground color information for each line from the memory. By reading the background information and analyzing the histogram, a definite value (ground color image data) of the ground color component of the document is detected. By providing the background detection processing device 110 outside the image processing unit 20, more advanced analysis processing and switching of analysis methods are facilitated. For example, it is convenient when the image processing unit 20 shown in FIG. 2 is configured by a semiconductor integrated circuit.

  As described above, the output color component (for example, toner color component; yellow color in the previous example) that has a great influence on human visual characteristics is set as the first color, and an image outside the image processing unit 20 is used for the first color. A method of executing through print processing that omits processing or omits image compression and expansion processing, ground color removal processing by ground color detection processing that can acquire ground color information at high speed, A method of executing ground color removal processing using this fixed value when a fixed value of ground color information with high accuracy is obtained is executed by hardware mounted on a semiconductor integrated circuit (IC, for example). It can also be executed by software.

  When these series of methods are executed by software, the program that constitutes the software has functions such as a computer (embedded microcomputer, etc.), CPU, logic circuit, storage device, etc., embedded in dedicated hardware. A system on a chip (SOC) that is mounted on a single chip to achieve a desired system, or a general-purpose personal computer capable of executing various functions by installing various programs. It is installed from a recording medium on a computer or the like.

  This recording medium causes a change state of energy such as magnetism, light, electricity, etc. to a reading device provided in the hardware resource of a computer in accordance with the description contents of the program, and a corresponding signal format. Thus, the description content of the program can be transmitted to the reading device. For example, a magnetic disc (including a flexible disc), an optical disc (CD-ROM (Compact Disc-Read Only Memory)), a DVD (which is distributed to provide a program to a user separately from a computer, (Including Digital Versatile Disc), magneto-optical disc (including MD (Mini Disc)), or package media (portable storage media) made of semiconductor memory, etc. It may be configured by a ROM, a hard disk, or the like in which a program is recorded that is provided to the user in a state. Or the program which comprises software may be provided via communication networks, such as a wire communication or radio | wireless.

  For example, a storage medium in which a program code of software that realizes the functions of the above-described embodiments is supplied to a system or apparatus, and the computer (or CPU or MPU) of the system or apparatus stores the program code in the storage medium. The effect described in the above embodiment can also be achieved by reading and executing. In this case, the program code itself read from the storage medium realizes the functions of the above-described embodiment.

  Further, by executing the program code read by the computer, not only the functions of the above-described embodiments are realized, but also an OS (operating system; basic software) running on the computer based on the instruction of the program code. ) May perform a part or all of the actual processing, and the functions of the above-described embodiments may be realized by the processing.

  Further, after the program code read from the storage medium is written in a memory provided in a function expansion card inserted into the computer or a function expansion unit connected to the computer, the function expansion is performed based on the instruction of the program code. There may be a case where the CPU or the like provided in the card or the function expansion unit performs part or all of the actual processing, and the functions of the above-described embodiments are realized by the processing.

  The program is provided as a file describing the program code that realizes the processing described in the above embodiment. In this case, the program is not limited to being provided as a batch program file, but depending on the hardware configuration of the system. May be provided as individual program modules.

  As mentioned above, although this invention was demonstrated using embodiment, the technical scope of this invention is not limited to the range as described in the said embodiment. Various changes or improvements can be added to the above-described embodiment without departing from the gist of the invention, and embodiments to which such changes or improvements are added are also included in the technical scope of the present invention.

  Further, the above embodiments do not limit the invention according to the claims (claims), and all combinations of features described in the embodiments are not necessarily essential to the solution means of the invention. Absent. The embodiments described above include inventions at various stages, and various inventions can be extracted by appropriately combining a plurality of disclosed constituent elements. Even if some constituent requirements are deleted from all the constituent requirements shown in the embodiment, as long as an effect is obtained, a configuration from which these some constituent requirements are deleted can be extracted as an invention.

  For example, in the image compression memory functions shown in the first to fourth examples, the through print processing and immediacy are performed only for the Y color component of the output color component YMCK that is less affected by the image quality on human visual characteristics. However, the present invention is not limited to this, and it is not limited to this. For output color components (which may be plural) that have relatively little influence on image quality, While performing ground color removal processing by ground color detection processing with excellent immediacy, it is normal for output color components that are relatively affected by image quality (excluding output color components that are less affected by image quality) What is necessary is just to process. For example, for the C color component that is less influenced by the image quality on the visual characteristics next to the Y color, the ground color removal process by the through print process or the ground color detection process that is excellent in immediacy may be executed. However, in this case, the image quality is deteriorated as compared with the above embodiment.

  In the image compression memory functions of the third and fourth examples, an output color component (for example, Y of YMCK) that is less affected by the image quality on the human visual characteristics and an output color component that is more affected by the human visual characteristics. Among the Y color components (for example, MCK of YMCK), the ground color removal processing by the real-time AE background detection is executed for the Y color component that is less influenced by the image quality on human visual characteristics, while the remaining output color component (MCK) However, the present invention is not limited to this example, and is not limited to this example. For output color components with little influence of image quality, a ground color excellent in immediacy is used. While performing the ground color removal processing by the detection processing, the remaining output color components may be ground color removal processing that can detect ground color information with high accuracy even though acquisition takes time. It may be used any Kenchi methods and removal methods.

  In other words, in consideration of human visual characteristics (visual sensitivity), when performing ground color removal processing of different methods for each of multiple output color components used to output a color image, The combination of the ground color detection processing method and ground color removal processing method for the output color component that has a small effect on image quality and the output color component that has a large effect on image quality on human visual characteristics is the final image quality required. Depending on the, various combinations are possible.

  In the image compression memory functions of the third and fourth examples, the relation to the ground color removal process as an example of the automatic exposure (AE) function has been described. However, the background of the document is not limited to the ground color removal process. The same applies to the relationship with density adjustment with reference to information.

  In the image compression memory functions of the first to fourth examples, the output color component that has little influence on the image quality on human visual characteristics is first output in the tandem image output unit (the first color and Specifically, the first color (Y) → the second color (M) → the third color (C) → the fourth color (K), so that the image quality is maintained at the same level as the conventional one. However, the output processing time from when the output command is issued to when the output is discharged is described as being shortened. However, when image quality deterioration is allowed, other arrangement orders may be used. For example, the first color (C) → the second color (M) → the third color (Y) → the fourth color (K), or the first color (K) → the second color (Y) → the third color (M) ) → 4th color (C) or the like.

  In the image compression memory functions of the first to fourth examples, the page memory processing device 910 uses device-independent Lab color space image data as data to be stored in the page memory. The target data is not limited to image data in the Lab color space, and may be, for example, RGB data (input-side device-dependent image data) before conversion into the Lab color space read by the image acquisition unit 10. Alternatively, image data (output-side device-dependent image data; YMCK in the previous example) converted into a color space corresponding to the output side (image output unit 30) may be used.

  Further, the idea of the present invention is to execute a process that can be performed in a shorter time than a normal process for one color component of a plurality of color components constituting a color image. For the other color component, the normal processing is executed, and as long as this is the case, how the image path route is taken is arbitrary. “Performing in a shorter time than normal processing” is relative, and various methods can be employed as shown in a modification in FIG. 11, for example.

  For example, in the example shown in FIG. 11A, five image processing function units (A, B, C, and D, respectively) that execute different processes in the image path route as the normal process for each of the M, C, and K color components. , E) are provided in cascade, whereas in the image path route for the Y color component performed in “shorter time than normal processing”, at least one of five (B, D in the figure) is provided. The “short time” process is realized by deleting the process (2). That is, the short-time processing system is configured to delete processing blocks. This configuration is based on the same concept as that shown in FIG.

  In the example shown in FIG. 11B, the image path route as a normal process is the same as that in FIG. 11A, whereas at least one of the five (in the figure, B and D 2). The “short time” processing is realized by allowing the inside to pass through without passing a delay or with a smaller delay than the normal route.

  In the above-described embodiment, the copying apparatus has been described as an example. However, the above-described embodiment is also applied to any image forming apparatus that can output a color image to a predetermined output medium, such as a printing apparatus (printer) or a facsimile apparatus. It is applicable to.

1 is a mechanism diagram of an example of a color copying apparatus equipped with an embodiment of an image processing apparatus according to the present invention. 2 is a block diagram of an embodiment of an image processing unit provided in the color copying apparatus having the above configuration. FIG. It is a figure explaining the page memory processing apparatus provided with the image compression expansion process function used in order to implement | achieve the image compression memory function in the image processing part shown in FIG. It is a figure explaining the 1st example of an image compression memory function. It is a figure explaining the 2nd example of an image compression memory function. It is the block diagram which showed the structural example of the page memory processing apparatus provided with the image compression expansion process function used in order to implement | achieve the image compression memory function of the 2nd example. It is a figure explaining the 3rd example of an image compression memory function. It is a figure explaining the effect of the image compression memory function of the 3rd example. It is a figure explaining the 4th example of an image compression memory function. It is the block diagram which showed the example which applies an image compression memory function to the image processing part provided with one stage of ground color removal processing functions. It is a figure explaining the modification of an image path route.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Color copying apparatus, 10 ... Image acquisition part, 11 ... Platen glass, 12 ... Light source, 13 ... Light-receiving part, 14 ... Signal processing part, 20 ... Image processing part, 20a ... Pre-stage image processing part, 20b ... Post-stage image processing , 20c ... peripheral part, 30 ... image output part, 31 ... image forming part, 32 ... photosensitive drum, 102 ... ground color detection part, 110 ... background detection processing apparatus, 400 ... previous color adjustment part, 500 ... color conversion , 600: Subsequent color adjustment unit, 602: Subsequent background color removal processing unit, 800 ... Data IF unit, 801 ... Path switching unit, 910 ... Page memory processing device, 912 ... Encoding unit, 914 ... Image memory unit, 916 ... Decoding unit, 918 ... Output unit

Claims (18)

A process that can be performed in a shorter time than a normal process is performed for one color component of a plurality of color components constituting a color image, and the other color component of the plurality of color components is performed. An image processing method characterized by executing the normal processing. After performing the process for the one color component to form an image represented by the one color component, the process for the other color component is performed to obtain an image represented by the other color component. The image processing method according to claim 1, wherein the image processing method is formed. The image processing method according to claim 1, wherein at least a part of the processing performed in the normal processing is omitted for the one color component. The image processing method according to claim 3, wherein the processing to be omitted includes image processing related to image quality improvement. The normal process includes a process of compressing an image, temporarily storing the image in an image memory, and then performing an expansion process corresponding to the compression process on the image read from the image memory. The image processing method according to claim 3 or 4. The image processing method according to claim 5, wherein the compression process and the expansion process are omitted for the one color component. The color image is an image representing a document read by a predetermined reading device,
Detection processing for detecting the background color information of the document with an emphasis on accuracy is the normal processing,
The image processing method according to any one of claims 1 to 6, wherein for the one color component, a detection process is performed with an emphasis on a detection speed of ground color information of the document. For the one color component, a detection process that emphasizes the detection speed of the background color information of the document is performed, and a detection process that detects the background color information of the document with an emphasis on the accuracy is performed,
When a detection result obtained by detecting the background color information of the document with an emphasis on the accuracy is obtained, a detection process is performed on the one color component with an emphasis on a detection speed of the background color information of the document, and the color 8. The image processing according to claim 7, wherein the image processing is switched from processing for forming an image to processing for forming the color image using a detection result obtained by detecting ground color information of the document with an emphasis on the accuracy. Method. The image processing method according to any one of 1 to 8, wherein the one color component is a component that has little influence on image quality in terms of human visual characteristics. An image processing system for forming a color output image corresponding to the input color image after performing desired image processing on the input color image,
A first processing unit that executes a process that can be performed in a shorter time than a normal process for one of the plurality of color components used to form the color output image;
An image processing system comprising: a second processing unit that executes the normal processing for the other color component of the plurality of color components. Each image forming unit corresponding to the plurality of color components is arranged in a tandem type,
The first processing unit executes processing for the one color component, and an image represented by the one color component is formed on a predetermined output medium by the image forming unit corresponding to the one color component. After that, the second processing unit executes processing for the other color component, and an image represented by the other color component is displayed on the output medium by the image forming unit corresponding to the other color component. The image processing system according to claim 10, wherein the image processing system is formed as follows. A main image processing apparatus comprising: an image processing unit that performs desired image processing on an input color image; and a path switching unit that switches an image path of the input color image;
Sub-image processing that is used as a switching destination switched by the path switching unit and performs a desired process on a color image input from the main image processing apparatus and then returns to the main image processing apparatus With equipment and
The second processing unit is configured by the cooperation of the main image processing device and the sub image processing device, and the main image processing device is configured to receive the input color via the path switching unit. The process of transferring an image to the sub-image processing device, performing the desired processing in the sub-image processing device, and returning to the path switching unit is the normal processing.
The first processing unit is configured such that the path switching unit of the main image processing apparatus operates so as to omit the process of switching the image path for the one color component and executes the high-speed processing. The image processing system according to claim 10 or 11, wherein: The color image is an image representing a document read by a predetermined reading device,
The second processing unit includes a first ground color detection unit that detects ground color information of the document with an emphasis on accuracy, and the other ground based on information detected by the first ground color detection unit. A first image processing unit that performs predetermined image processing on color components,
The first processing unit includes a second ground color detection unit that executes detection processing that places importance on the detection speed of the ground color information of the document for the one color component, and the second ground color detection unit. 13. The apparatus according to claim 10, further comprising: a second image processing unit that performs predetermined image processing on the one color component based on the detected information. Image processing system. The second ground color detection unit executes detection processing that places importance on the detection speed of the background color information of the document for the one color component, and the first ground color detection unit places importance on the accuracy. Execute detection processing to detect the background color information of the document,
The first processing unit uses the detection result obtained by placing importance on the detection speed obtained by the second ground color detection unit, and outputs the color output image based on an image processed by the second image processing unit. Is started on the output medium, and when the first ground color detection unit obtains a detection result that emphasizes the accuracy, the accuracy is emphasized from the detection result that emphasizes the detection speed. The color output image is formed on the output medium based on an image processed by the second image processing unit by using a detection result focusing on accuracy and switching to a detection result. Item 14. The image processing system according to Item 13. The image processing system according to any one of 10 to 14, wherein the one color component is a component that has little influence on image quality on human visual characteristics. An image processing system used for forming a color output image corresponding to the input color image on a predetermined output medium after performing desired image processing on the input color image, One color component used for forming a color output image on the output medium is processed at a speed higher than that of normal processing, and the other of the plurality of color components is executed. An image processing apparatus used in a system for executing the normal processing for the color components of
An image acquisition unit for acquiring a color image representing a document read by a predetermined reading device;
An image processing unit that performs desired image processing on the color image acquired by the image acquisition unit;
A path switching unit that switches an image path of the input color image;
A first ground color detection unit for detecting ground color information of the document with an emphasis on accuracy;
A first image processing unit that performs predetermined image processing on the other color component based on information detected by the first ground color detection unit;
A second ground color detection unit that executes detection processing that places importance on the detection speed of the ground color information of the document for the one color component;
An image processing apparatus comprising: a second image processing unit that performs predetermined image processing on the one color component based on information detected by the second ground color detection unit. The image processing apparatus according to claim 16, wherein the path switching unit omits the process of switching the image path for the one color component. An image processing system used for forming a color output image corresponding to the input color image on a predetermined output medium after performing desired image processing on the input color image, One color component used for forming a color output image on the output medium is processed at a speed higher than that of normal processing, and the other of the plurality of color components is executed. An image processing apparatus used in a system for executing the normal processing for the color components of
A compression processing unit that performs compression processing on a color image of the other color component;
A first image storage unit that stores a color image for the other color component, and a second image storage unit that stores a color image that has been compressed for the other color component compressed by the compression processing unit. An image storage unit,
A decompression processing unit that decompresses a color image that has been compressed for the other color component read from the second image storage unit;
A first image processing unit that performs image processing related to image quality improvement on a color image of the one color component read from the first image storage unit;
An image processing apparatus comprising: a second image processing unit configured to perform image processing related to image quality improvement on a color image of the other color component expanded by the expansion processing unit.

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