JPH1198343A - Image processor and image processing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce circuit scale by reducing the capacity of a memory and reducing the width of a bus transfer by imparting the color data of a chrominance signal selected by the selection information of respective pixels in a prescribed image area included in a color select signal to the respective pixels according to the selection information, thereby expanding the compressed image data into multilevel image data for the unit of a pixel. SOLUTION: An image processing means 16 performs image processing to the compressed image data consisting of the chrominance signal containing specified information to be used for expressing a prescribed image and the color select signal containing the selection information for selecting the specified information out of the chrominance signal concerning the respective pixels in the prescribed image area. The compressed image data, to which image processing is performed by the image processing means 16, are expanded to the multilevel image data for the unit of a pixel by an expanding means 14 by applying the color data of the chrominance signal in the compressed image data selected by the selection information to the respective pixels according to the selection information of the respective pixels in the prescribed image area contained in the color select signal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image processing apparatus for decompressing compressed image data and outputting it to an image output apparatus, and more particularly to an image processing apparatus suitable for a color printer, a facsimile, and the like.

[0002]

2. Description of the Related Art Conventionally, an image processing apparatus has been used which decompresses compressed image data sent from a computer or the like, performs appropriate processing on the decompressed image data, and outputs it to an image output device. Hereinafter, a conventional image processing apparatus will be described using a printer as an example.

FIG. 21 is a schematic block diagram for explaining a conventional printer.

[0004] The computer 8 compresses bitmap image data 85 to be output to the printer 9 by a compression section 86 realized by a printer driver or the like.
7 is stored. Thereafter, the data is output to the printer 9 via a data transfer unit (not shown).

[0005] In the printer 9, when the printer controller 91 receives the compressed image data from the computer 8, it stores it in the image memory 93. Then, after the data is converted into bitmap image data 95 by the decompression unit 94,
The image processing section 96 performs necessary image processing such as color correction, color conversion, or edge processing, and outputs the result to a printer engine (image forming portion of the printer) 92. In response to this, the printer engine 92 sets the printer controller 9
A print image is generated in accordance with the image data received from the printer 1.

[0006]

By the way, in the above-mentioned conventional image processing apparatus, color correction or color correction is performed on bitmap image data in which the image data of each pixel is composed of multi-values (a plurality of bits, for example, 8 bits). Necessary image processing such as color conversion or edge processing is performed. For this reason, there is a problem that a large capacity memory is required to store the bitmap image data.

For example, in a conventional image processing apparatus, an edge determination for detecting an edge by examining a gray level difference between an arbitrary pixel and a pixel adjacent to the pixel is performed on the bitmap image data stored in the memory as follows. I'm going in the way.

FIG. 22 is a diagram for explaining the flow of edge determination processing in a conventional image processing apparatus. Here, a case where 8-bit multi-valued image data per pixel is handled will be described.

First, the image data of the pixel for which the edge is to be determined and the surrounding image data are stored in a multi-valued memory. Then, a difference between the image data of the pixel for which the edge determination is to be performed and the surrounding image data is obtained, and it is determined whether or not the difference is equal to or more than a predetermined amount.

When a 3 × 3 multi-valued memory group as shown in FIG. 23 is used as a memory for storing bitmap image data, image data of a pixel for which edge determination is to be performed is read out from the multi-valued memory D22 and the edge is determined. The image data around the pixel to be determined is stored in multivalued memories D11, D13, D31,
Read from D33. Then, the values of the image data of the pixels stored in the multi-level memory D22 and the multi-level memories D11 and D11
The difference from the average value of the image data of the pixels stored in D13, D31 and D33 is calculated, and if the difference is equal to or more than a predetermined amount, the pixel stored in the multi-valued memory D22 is determined as an edge. Alternatively, as shown in FIGS. 24 and 25, the difference between the image data of the pixel for which edge determination is performed and the average value of the image data of eight surrounding pixels is calculated, and whether the difference is larger than the threshold value is determined. To determine the edge.

This method is generally used in digital filters.

As described above, in the conventional image processing apparatus, the edge judgment is performed by calculating the multi-valued image data using the digital filter. Therefore,
A large memory for storing multi-valued image data is required.
Further, in order to perform the edge determination, it is necessary to store at least three lines of image data in the multi-valued memory, so that the bus width for transferring the image data is increased.

In the above-described conventional image processing apparatus, necessary image processing such as color correction, color conversion, or edge processing is sequentially performed on the bitmap image data for each processing. Therefore, there is a problem that it takes time to perform all necessary image processing.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to reduce a memory capacity required for image processing and reduce a bus width for transferring image data to reduce a circuit width. An object of the present invention is to provide an image processing device capable of reducing the scale.

[0015]

In order to solve the above-mentioned problems, an image processing apparatus according to the present invention provides, for each predetermined image area, identification information for identifying at least one color used to represent the predetermined image. And a color selection signal including selection information for selecting the specific information from the color signals for each pixel in the predetermined image area. The compressed image data subjected to the image processing by the image processing means, and the compressed image data according to the selection information of each pixel in a predetermined image area included in the color selection signal of the compressed image data, Decompression means for decompressing pixel-level multivalued image data by assigning, to pixels, color data specified by specific information included in a color signal of the compressed image data selected by the selection information , Characterized in that it comprises.

Here, the image processing means changes the arrangement of the selection information of each pixel contained in the color selection signal,
A color selection signal processing unit for rotating or enlarging / reducing an image may be provided.

When the color signal has color data as specific information, the image processing means performs a color correction process such as color conversion or gamma correction on the color data contained in the color signal. It may have signal processing means.

Further, when the color signal has a color pallet number for specifying color data from a color pallet table having a plurality of color data as specific information, the image processing means is included in the color pallet table. A color palette table processing means for performing color correction processing such as color conversion and gamma correction on color data may be provided.

According to the present invention, with the above-described configuration, necessary image processing is performed before decompressing the compressed image data. For this reason, the capacity of the memory required for image processing can be reduced, and the circuit scale can be reduced.

Further, according to the present invention, different image processing can be performed in parallel on the color signal and the color selection signal, respectively, so that the time required for the image processing can be shortened.

In the present invention, a feature judging means for judging the feature of the target pixel by examining the shade of color between the target pixel and the pixels surrounding the target pixel, and a judgment result of the feature judging means. And a halftone processing unit that outputs multi-valued image data in pixel units expanded by the expansion unit and that has been subjected to halftone processing according to.

Note that the characteristic determining means examines the color shading between the target pixel and the pixels surrounding the target pixel based on the multi-valued image data in pixel units expanded by the expansion unit. The feature of the target pixel may be determined.

Alternatively, when the color signal has color data as specific information, the shade of the color between the target pixel and the pixels surrounding the target pixel is represented by the color data contained in the color signal and the color data. The feature of the target pixel may be determined by checking based on the selection information included in the selection signal.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a first embodiment of the present invention will be described.

Here, a case where the image processing apparatus is applied to a printer will be described. However, the present invention can be applied to various image output apparatuses such as a facsimile and a monitor in addition to a printer.

FIG. 1 is a schematic block diagram for explaining a printer according to a first embodiment of the present invention.

The computer 1 converts bitmap image data 21 to be output to the printer 2 into compressed image data comprising a color signal and a color selection signal by a compression unit 22 realized by a printer driver or the like. It is stored in the memory 23. Thereafter, the data is output to the printer 1 via a data transfer unit (not shown).

Here, the color signal is a signal for specifying a plurality of colors when various colors used in a predetermined image area (for example, 4 × 4 pixels) are approximated by a plurality of colors. is there. The compression unit 22 approximates various colors in the image area specified by the bitmap image data 21 to a plurality of colors by an operation in consideration of a color space. Then, the color signals are generated by arranging data indicating a plurality of similar colors in a predetermined order.

The color selection signal is a signal for selecting a color of each pixel in a predetermined image area (for example, 4 × 4 pixels) from the color signals. For each pixel in the image area specified by the bitmap image data 21, the compression unit 22 includes information (color data corresponding to the corresponding color data) that specifies color data close to the color of the pixel from the plurality of color data included in the color signal. Are described in pixel order, and a color selection signal is generated.

FIG. 2 is a diagram for explaining an example of the structure of compressed image data when a color in a predetermined image area is approximated to a plurality of colors by an operation taking a color space into consideration. Here, 22a indicates the data configuration of the color signal, and 22b indicates the data configuration of the color selection signal.

In the example shown in FIG. 2, the color signal approximates the colors used in the predetermined image area to two colors of color 0 and color 1 by an operation considering the color space.

More specifically, as shown in FIG. 3, each pixel in a predetermined image area is developed in a color space using RGB as coordinate axes (FIG. 3A). Then, the space is divided into two by a certain surface S, so that the pixels are classified into two groups, and a color 0 and a color 1 (for example, an average value of the pixels belonging to the group) representing each group are set. (Figure 3
(B)). When each RGB color is represented by 8-bit data,
As shown in FIG. 2, the color signals are 24 for both color 0 and color 1.
Bits, for a total of 48 bits.

When the colors in the predetermined image area are approximated by four colors, the color space may be divided by any two surfaces, and each pixel in the predetermined image area may be divided into four groups. Then, a color representative of each group may be set.

In the color selection signal, for each pixel in the predetermined image area, information (number) for specifying an approximate color of the pixel (a color representative of a group to which the pixel belongs) is arranged in a predetermined order. It is configured. As shown in FIG.
When the color signal is composed of two colors, color 0 and color 1,
The color selection signal is one bit per pixel. When the color signal is composed of four colors, the color selection signal has 2 bits per pixel.

When each color of RGB is 8-bit data,
Since the number of bits of 4 × 4 pixel bitmap image data is 24 bits per pixel, 24 × 16 =
This is 384 bits. On the other hand, according to the compressed image data shown in FIG. 2, the bitmap image data of 4 × 4 pixels can be compressed into a total of 64 bits of 48 bits of the color signal and 16 bits of the color selection signal.

The method of compressing and expanding image data used in the present embodiment is described in detail in Japanese Patent Publication No. 6-7688.

Returning to FIG. 1, the description will be continued.

When the printer 1 receives the compressed image data having the above configuration from the computer 2, the printer 1 operates as follows.

First, in the printer controller 11, the image memory 13 stores the received compressed image data. Next, the image processing unit 16 causes the image memory 13
Necessary image processing such as color correction and pixel rearrangement is directly performed on the compressed image data stored in. After that, the decompression unit 14 decompresses the data into multivalued image data in pixel units.

After the decompression process in the decompression unit 14 is completed, the halftone processing unit 17 reproduces a halftone based on the decompressed image data. Thereafter, the image is output to a printer engine (image forming portion of the printer) 12. In response, the printer engine 12 generates a printed image according to the data received from the printer controller 11.

In the present embodiment, as the compressed image data, a color signal for specifying a plurality of colors approximating various colors used in the predetermined image area, and each pixel in the predetermined image area And compressed color data comprising a color selection signal in which information for selecting a color from the color signals is arranged in a predetermined order.

Therefore, color conversion from RGB (red, green, blue) to YMCK (yellow, magenta, cyan, black) and the like, intermediate color correction, and other color corrections can be performed directly from color signals. it can. Processing involving pixel rearrangement, such as image rotation and enlargement / reduction, can be performed directly from the color selection signal. Further, the image area separation processing based on the determination of a feature point such as an edge can be performed by using both a color signal and a color selection signal. That is, it is possible to determine whether or not there is shading of an image in a predetermined image area using a color signal, and it is possible to extract a color transition in the predetermined image area using a color selection signal. Therefore, by using both pieces of information, it is possible to extract a feature point in the predetermined image area.

Therefore, in the present embodiment, the required image processing is performed before decompressing the compressed image data by using the compressed image data having the above configuration. For this reason, the capacity of the memory required for image processing can be reduced, and the circuit scale can be reduced. In the present embodiment, the color correction process and the process involving the rearrangement of pixels can be performed directly from the color signal and the color selection signal, respectively, so that these processes can be performed in parallel. Therefore, the time required for image processing can be reduced.

Further, the compressed image data having the above configuration has a feature that the compression efficiency (data length of the compressed data) is always constant. For example, according to the compressed image data shown in FIG. 2, bitmap image data of 4 × 4 pixels is always compressed to 64 bits.

Therefore, according to the present embodiment, the operations from the reading of the compressed image data from the image memory 13 to the halftone processing in the halftone processing unit 17 are performed by the printer controller 11 at the request timing of the printer engine 12. Therefore, they can be performed in synchronization. That is, a speed conversion buffer (memory 95 shown in FIG. 21)
Need to be provided).

As described above, the compression / decompression processing of the multi-valued image data in the present embodiment is described in Japanese Patent Publication No. 6-76.
No. 88, and the method of realizing it may be either hardware or software.

Next, the printer controller 11 which is a main part of this embodiment will be described in detail. FIG. 4 shows FIG.
FIG. 3 is a block diagram illustrating a configuration of the printer controller 11 shown in FIG.

In the configuration shown in FIG. 1, the printer engine 12 is the same as that conventionally used in a printer, and therefore, the details of this portion are omitted.

First, the image processing section 16 will be described.

As shown in FIG. 4, the image processing section 16 includes a color signal calculation section 161, a color selection signal calculation section 162, a color determination section 163, a feature point determination section 164, and an image processing selection section 165. Consists of

The color signal calculator 161 performs color conversion, color adjustment,
Alternatively, color correction such as halftone correction is performed on the color signal. FIG. 5 is a configuration block diagram of the color signal calculation unit 161 shown in FIG. Here, 161a is a color correction unit, 161b
Is a color conversion unit, 161c is a halftone correction unit, and 161d
Reference numerals 161f to 161f denote memories for storing correction data used by the color correction unit 161a, the color conversion unit 161b, and the halftone correction unit 161c, respectively.

The color correction section 161a performs a process for correcting a color signal to a color suitable for the printer engine 12.
Generally, the printer engine 12 has device-specific color characteristics. Therefore, the image output from the printer engine 12 may change from the color specified by the color signal. The color correction unit 161a is to solve such a problem. The color data included in the color signal is corrected according to the color characteristics of the printer engine 12. As a color correction method, a method based on a matrix operation or a table reference is generally used, but other methods may be used. If the color characteristics change depending on the state of the printer engine 12, the memory 1
It is preferable to change the color correction data by referring to the color correction data stored in 61d.

The color conversion unit 161b converts color data included in a color signal from data composed of three colors of RGB mainly used in a monitor or the like to four colors of YMCK mainly used in a printer or the like. Convert to composed data. This conversion process is a process of generating one color in YMCK based on data of three colors of RGB. The color conversion processing is a technique that has been conventionally used, but a general method is to use RGB as a complementary color of CMY. In this method, the undercolor removal processing (UCR) and the black generation processing (BG) are performed by combining three colors of CMY. In addition, a method of performing color conversion by storing a color conversion table in the memory 161e and referring to the table,
There is a method of performing color conversion by a matrix operation.

In this embodiment, the case where the present invention is applied to a printer controller is described.
When the output destination of the image data does not need to perform color conversion such as on a monitor, the color conversion unit 161b may not be provided.

The halftone correction section 161c is provided with a color correction section 161.
In the color signal a and the color conversion unit 161b, a process of improving halftone reproducibility is performed on the color signal that has been subjected to the color correction and the color conversion process. This process is generally called gamma correction.

The color data included in the color signal is configured on a full scale in order to reproduce colors faithfully. For example, if each color of CMYK has a bit number of 8 bits, each color has 256 levels of data from 0 to 255. However, an image forming apparatus such as a printer may be able to reproduce a halftone only in an arbitrary range. For example, a certain printer can express a halftone only in the range of 50 to 200 out of 256 levels from 0 to 255, and if it is less than 50, it will be pure white, and if it is more than 200, it will be a color whose density will not increase any more. There is. In such a printer, when one color (any of CMYK) constituting certain color data has a value of 208, it is necessary to prevent the color from becoming a color whose density does not increase any more. . The halftone correction unit 161c converts the color data having 256 gradations for each color into the halftone reproduction range (50 to 20) of the printer.
Correction is made so as to assign to 0), thereby preventing the above problem from occurring.

The method of halftone correction is generally based on a matrix operation or referring to a table, but may be based on other methods. When the halftone characteristic changes depending on the state of the printer engine 12, it is preferable to change the halftone characteristic by referring to the halftone correction data stored in the memory 161f.

Next, the color selection signal calculation section 162 will be described.

The color selection signal calculation unit 162 performs processing involving pixel rearrangement such as image rotation and enlargement / reduction.

Regarding the rotation of the image, the order of the data of each pixel constituting the color selection signal may be changed. For example, the data of each pixel constituting the color selection signal is exchanged according to the rotation angle and the rotation direction of the image such as 90 degrees, 180 degrees, and 270 degrees. This processing is basically the same as a technique conventionally used as image rotation, but conventionally, processing has been performed on bitmap image data in which each pixel has color data. The present embodiment is different in that each pixel performs processing on a color selection signal including only color data selection information from a color signal. It is easier to replace a color selection signal with fewer bits than to replace data using bitmap image data. Therefore, in the present embodiment, the circuit scale can be reduced. As for the image rotation processing, instead of exchanging the data of each pixel constituting the color selection signal in the color selection signal calculation section 162, the expansion section 14 converts the color selection signal from the image memory 13 into Call order,
A method of changing according to the rotation information of the image is also conceivable.

The enlargement of the image is performed, for example, by inserting the same data as the data of the adjacent pixels between the data of each pixel constituting the color selection signal. For image reduction, for example, a method of reconstructing a color selection signal by extracting data of a pixel corresponding to each pixel after reduction from data of each pixel forming a color selection signal, or a method of reconstructing a color selection signal There is also a method of reconstructing the reduced color selection signal so that the data distribution on the map when the data of each pixel constituting the pixel is developed on the map is as similar as possible. Alternatively, a method using dither processing can be used. These processes are basically the same as those conventionally used for image enlargement / reduction, but conventionally, processes have been performed on bitmap image data in which each pixel has color data. On the other hand, the present embodiment is different in that each pixel processes a color selection signal including only color data selection information from a color signal.
In the present embodiment, the circuit scale can be reduced because the number of bits handled is smaller than in the case where bitmap image data is used.

Next, the color judgment section 163 will be described.

The color determination unit 163 determines whether or not the color in the image area specified by the color signal has shading by referring to each color data included in the color signal. FIG. 6 shows the color determination unit 163 and the feature point determination unit 16 shown in FIG.
FIG. 4 is a schematic block diagram of FIG.

As shown in FIG. 6, the color determining section 163 has a color difference calculating section 163a and a shading determining section 163b.

The color difference calculator 163a calculates a color difference between a plurality of color data included in the color signal. For example, in the case of the compressed image data shown in FIG. 2, a color difference is calculated between two colors, color 0 and color 1, which are color signals.

The density determining means 163b is provided with the color difference calculating section 16
The color shading is determined based on the color difference obtained in 3a. And
For each of the color data included in the color signal, identification information (binary data) indicating whether the color specified by the data is a dark color or a light color is sent to the feature determination unit 16.
Send to 4.

Next, the feature determining section 164 will be described.

As shown in FIG. 6, the characteristic point judging section 164 includes a gray level binary data memory 164a and a characteristic point extracting section 1.
64b.

The grayscale binary data memory 164a stores the grayscale determination result (determination of dark color or light color) of each color data included in the color signal sent from the color determination unit 163.

The feature point extracting section 164b outputs the shading result of the color data corresponding to the data of each pixel (the number for selecting the color data from the color signal) included in the color selection signal,
By examining using the value data memory 164a, a pixel serving as a feature point is determined.

Generally, edges to be extracted as feature points are
It is composed of darker pixels than the surroundings. Therefore, the feature point extracting unit 164b obtains the shading result of the pixel for which the feature point is to be determined and the shading results of surrounding pixels from the grayscale binary data memory 164a, so that the pixel for which the feature point is to be determined is determined. It is determined whether the color is darker than the surrounding pixels.

Here, the processing in the color judgment section 163 and the feature point judgment section 164 will be described in more detail.

First, the case where the color signal contains two color data will be described.

FIG. 7 shows a case where the color signal includes two pieces of color data, and
FIG. 6 is a diagram for explaining a flow of processing in No. 4;

First, the color difference calculation processing section 163a calculates a color difference between two color data included in a color signal for each of RGB colors (difference detection).

Next, the density determining unit 163b checks the sign (positive or negative) of the color difference obtained by the color difference calculating unit 163a,
With respect to two color data included in the color signal, the shading of the color is determined. Also, it is determined whether or not the absolute value of each color difference is larger than a predetermined threshold (shading determination).

Next, the feature point determination unit 164 determines the data of each pixel (the number for selecting the color data included in the color signal) included in the color selection signal by the color determination of the color data corresponding to the data. The result is replaced with the shading result in the section 163.
Then, using a digital filter, a feature point is extracted in consideration of the shading result between adjacent pixels and the comparison result between the absolute value of the color difference between the pixels and the threshold value (edge determination).

FIG. 8 is a diagram showing a more detailed processing flow of the color judgment unit 163 shown in FIG.

In FIG. 8, R0, G0 and B0 are:
R1 and G1 represent data constituting one color data (color 0) of the two color data included in the color signal.
And B1 indicate data constituting the other color data (color 1).

The following description focuses on the R color among the RGB colors constituting the color data.

First, the difference (R0-R1) between the color 0 and the color 1 is calculated by the color difference calculating section 163a, and the sign of the obtained difference is determined as to whether the color 0 or the color 1 is a darker color. Is output as a flag indicating Also, the absolute value of the difference is output.

Next, the density determining section 163b compares the absolute value of the difference sent from the color difference calculating section 163a with a predetermined constant (threshold). Then, when the absolute value of the difference is larger than the constant, the flag output from the color difference calculation unit 163a is output via the selector, and the flag is set as an addition target in an addition process described later.

The above processing is similarly performed for the G color and the B color constituting the color data. Then, the flag obtained through the selector is added, and the sign of the addition result is
It is determined which of color 0 and color 1 is a dark color.
For example, when the color difference calculation unit 163a calculates the color difference by subtracting the color 1 from the color 0 for each of the RGB colors, if the addition result is positive, it is determined that the color 0 is a dark color, and the addition result is negative. In the case of, it is determined that the color 1 is a dark color. If the addition result is 0, it is determined that there is no difference between the color 0 and the color 1 for extracting a feature point.

Next, a case where the color signal includes three or more color data will be described.

FIG. 9 shows a color determination unit 163 and a feature point determination unit 16 when the color signal contains four color data.
FIG. 6 is a diagram for explaining a flow of processing in No. 4;

First, the color difference calculation processing section 163a calculates the color difference between the color data in each combination of two color data for each of the four colors included in the color signal (difference detection).

Next, the density determining unit 163b checks the sign (positive or negative) of the color difference obtained by the color difference calculating unit 163a,
For each combination of the two color data, color shading is determined (shading determination). Then, the shading results of each combination of the two color data are summarized in an inter-color difference table.

Next, the feature point judging section 164 develops the data of each pixel (the number for selecting the color data included in the color signal) included in the color selection signal on the map. Then, by referencing the inter-color difference table, the shading result between adjacent pixels is checked, and feature points are extracted based on the result (edge determination).

FIGS. 10 and 11 are diagrams showing a more detailed processing flow of the color determining section 163 shown in FIG. 9, and FIG. 10 shows the processing in the color difference calculating section 163a and FIG.
Indicates processing in the shading determination unit 163b.

First, as shown in FIG.
In 63a, the difference between the respective color data for each of the RGB colors of the four color data is calculated by brute force. FIG.
0 indicates a case where the difference between the color data of the four colors (R 0, R 1, R 2, and R 3) of the four colors (R 0, R 1, R 2, and R 3) is brute force. However, the same processing is performed for the G color and the B color.

Next, as shown in FIG.
63b, between each color data (between color 0 and color 1, color 1
8 between the colors 2 and 3, the colors 2 and 3, the colors 3 and 0, the colors 0 and 2, and the colors 1 and 3).
Perform the procedure described in Then, the result is written in the color difference table. In the inter-color difference table shown in FIG. 11, the numeral in the left column, for example, 01 indicates the shading judgment between the color 0 and the color 1, and the result is written on the right side. For example, when it is determined that the color 0 is darker than the color 1, a determination result “れ る” is written on the right side of the 01 column.
In the opposite case, the determination result “×” is written.

In the above description, the shading between the color data is determined for a plurality of color data included in the color signal. However, shading can be obtained by other methods.

FIG. 12 is a diagram for explaining another shading determination method when four color data are included in the color signal. Here, the four color data (color 0 to color 3) included in the color signal are rearranged in the order of darker color. Then, these color data are divided into two of a dark color and a light color. For example, a dark color threshold value (for example, an average value of four color data) is set, and the four color data are divided into a dark color and a light color based on the density threshold.
Divide into two. Alternatively, when the absolute value of the color difference between adjacent color data is the largest and is equal to or more than a predetermined value, the color data is divided into a dark color and a light color.

Next, the image processing selecting section 165 will be described.

The image processing selection unit 165 includes the feature point determination unit 1
Image area determination is performed based on the determination result at 64. It is preferable to perform different image processing, particularly halftone processing, on a pixel serving as a feature point, a pixel around the pixel, and a pixel farther away than the pixels around the pixel. For example, when a feature point is an edge, a line process is performed on a pixel serving as a feature point, a simple dither process is performed on pixels surrounding the feature point, and a pixel serving as a feature point is also placed around the pixel. It is preferable to perform halftone dither processing on pixels that are not certain pixels. Further, when the color data included in the color signal is a combination of clearly shaded colors such as a text and a line drawing, it is preferable to perform a smoothing process on a pixel serving as a feature point.

Therefore, in the image processing selecting section 165,
Image area determination is performed based on the determination result of the feature point determination unit 164, and the type of pixel (a feature point, a pixel around the feature point, or a pixel farther away from the surrounding pixels), It instructs the halftone processing unit 17 to perform appropriate processing according to the color difference between the color data included in the color signals.

Next, the extension unit 14 will be described.

The expansion unit 14 generates multi-valued image data in pixel units based on the color signal sent from the color signal calculation unit 161 and the color selection signal sent from the color selection signal calculation unit 162. First, color data (multi-valued data) is obtained from the color signal sent from the color signal calculation unit 161.
Then, a number is sequentially assigned to each of the acquired color data. Next, data (a number for selecting color data from the color signal) assigned to each pixel in the predetermined image area is obtained from the color selection signal. Then, for each pixel, the data assigned to the pixel is replaced with the corresponding color data. Thereby, multi-valued image data in pixel units is generated.

Next, the halftone processing section 17 will be described.

The halftone processing section 17 includes an image processing selecting section 16
In accordance with the instruction from 5, the halftone processing such as halftone dither processing, simple dither processing, and line processing is performed on the multi-valued image data in pixel units output from the decompression unit 14.

FIG. 13 is a block diagram showing the configuration of the halftone processing section 17 shown in FIG.

As shown in FIG. 13, the halftone processing section 17 performs halftone dither processing on the multivalued image data in pixel units output from the decompression section 14.
1, a halftone processing B unit 172 that performs simple dither processing,
A selector for selecting any one output from among the processing units 171 to 174 according to an instruction from the image processing selection unit 165, a halftone processing C unit 173 that performs line processing, a smoothing processing unit 174 that performs smoothing processing, and 175
And a halftone reproducing unit 176 that reproduces a halftone based on the multi-valued image data received via the selector 175.

Here, the case where four processes are performed as the halftone process has been described. However, the present invention is not limited to this number, and the content of the process is not limited to this. For example, when the feature point determination unit 164 determines only which of two image areas, an edge part and a non-edge part, a pixel belongs to, there are only two halftone processes.

As described above, the image processing selection unit 165
Instructs to select an appropriate process for the multi-valued image data of the pixel that has been determined by the determination unit 164 according to the determination result of the feature point determination unit 164. In response, the selector 175 selects any one output from the processing units 171 to 174 as the multivalued image data of the pixel that has been determined by the feature point determination unit 164.

For example, when the result of the determination by the feature point determination unit 164 indicates that the pixel to be determined is an edge, the selector 175 determines whether the halftone processing C unit 173 is an edge.
Is selected. As a result, the multi-valued image data of the pixel to be determined subjected to the line processing is output to the halftone reproducing unit 176. If the pixel to be determined is around the edge, the selector 175
, The halftone processing B section 172 is selected. As a result, the multi-valued image data of the pixel to be determined subjected to the simple dither processing is output to the halftone reproducing unit 176. If the pixel to be determined is a pixel far from the edge, the selector 175 selects the halftone processing A unit 171. As a result, halftone dither processing is performed on the multivalued image data of the pixel to be determined, and the result is output to the halftone reproduction unit 176. Also, the result of the determination by the feature point determination unit 164 indicates that the pixel to be determined is an edge and that the color is clearly shaded like a text or a line drawing (this Can be determined from the color difference between the color data obtained by the color determination unit 163).
5, the smoothing processing unit 174 is selected. As a result, the multi-valued image data of the pixel to be determined is subjected to the smoothing processing, and is output to the halftone reproducing unit 176.

The halftone reproducing section 176 reproduces a halftone based on the multi-valued image data in pixel units sequentially received via the selector 175. As a result, the multi-valued image data in pixel units is converted into an output signal suitable for the printer engine 12.

For example, in the case of a laser printer, serial data is generally output to a printer engine. In this case, the multi-valued image data is converted into serial data having a pulse amplitude and a pulse application time corresponding to the gradation indicated by the data. That is, by changing the pulse amplitude to change the light amount of the laser light, or changing the pulse application time to change the light emission time of the laser light, each pixel of the printed image has many pixels. The gradation is set according to the value image data. If the number of tones that can be reproduced in pixel units of the printed image is small, halftone reproduction using spatial modulation such as dither processing performed in the preceding halftone processing may be used together.

In the first embodiment of the present invention, as described above, color correction processing such as color conversion and pixel rearrangement processing such as image rotation are performed on compressed image data. Therefore, the number of bits to be handled can be greatly reduced as compared with the case where the above processing is performed on the decompressed image data, that is, multi-valued image data in pixel units. Therefore, according to the present embodiment, the memory capacity and data bus width required for the above processing can be reduced. Thereby, the circuit scale can be reduced. Also,
The time required for processing can be reduced.

In this embodiment, color correction processing such as color conversion and pixel rearrangement processing such as image rotation are performed in parallel with the color signal and the color selection signal, respectively. Therefore, the time required for image processing can be further reduced.

Furthermore, according to the present embodiment, since the compressed image data whose data length is always constant is used, the operation from the reading of the compressed image data from the image memory 13 to the halftone processing by the halftone processing unit 17 is performed. To the printer engine 1
2 in synchronization with the request timing. Therefore, it is not necessary to provide a speed conversion buffer.

In the above embodiment, the color signal processed by the color signal calculation section 161 and the color selection signal calculation section 16
The color selection signal processed in step 2 is directly output to the decompression unit 14. However, as shown in FIG. 14, the color signal processed by the color signal calculation unit 161 and the color selection signal processed by the color selection signal calculation unit 162 are temporarily stored in the image memory 18, and then stored in the decompression unit 14. You may make it output.

In this way, the color signals and the color selection signals stored in the image memory 13 need not be read out in order (for example, in the order of input to the image memory 13). By adjusting the reading, the color signal and the color selection signal can be output to the decompression unit 14 in order. For this reason, it is possible to execute processing of a color signal, which requires a long processing time, in advance.

In the above embodiment, the compressed image data sent from the computer 2 is temporarily stored in the image memory 13 and then subjected to image processing by the image processing section 16. However, the compressed image data sent from the computer 2 may be directly input to the image processing unit 16 without passing through the image memory 13. In the present embodiment, since the compressed image data having a fixed data length is used, even if the image memory 13 is not provided,
Image processing in the image processing unit 16 can be performed smoothly.

Further, in the above embodiment, the color signal of the compressed image data sent from the computer 2 is
The one including the color data of RGB has been described. However, the color data is not limited to this. For example, a color signal containing CMYK color data may be used as the color signal of the compressed image data sent from the computer 2. In this case, the color signal calculation unit 161
Is unnecessary.

In the above-described embodiment, the color conversion processing in the color signal calculation unit 161 has been described in which the color data of RGB is converted into the color data of CMYK. However, the color conversion processing in the color signal calculation unit 161 is not limited to this. What is necessary is to convert the color data of the color signal of the compressed image data sent from the computer 2 into color data according to the characteristics of the printer engine 12. For example, color data composed of RGB may be converted into color data composed of six colors obtained by adding light magenta and light cyan to CMYK.

Here, a specific circuit configuration example of the present embodiment will be described.

FIG. 15 is a diagram showing a circuit configuration of a printer controller to which the first embodiment of the present invention is applied.

In FIG. 15, among the compressed image data stored in the image memory 50, a color signal composed of color data of a plurality of colors approximated to colors in a predetermined image area by an operation using a color space is a color signal. The signal is input to the correction circuit 51. The color correction circuit 51 performs color correction according to the printer engine while referring to a color correction table stored in the memory 52. After that, it is input to the color conversion circuit 53.

The color conversion circuit 53 converts the color data included in the color signal from RGB data to YMCK data with reference to the color conversion UCR table stored in the memory 55 and the color conversion BG table stored in the memory 54. Convert. Thereafter, the color data of the color signal is subjected to gamma correction by a gamma correction circuit 56. Here, the printer engine 12
The gamma correction is performed with reference to the gamma correction table stored in the memory 57 in order to perform the halftone reproduction according to the above.

On the other hand, of the compressed image data stored in the image memory 50, a color selection number in which a number for selecting one color data included in the color signal is described for each image in the predetermined area. The signal is input to the image rotation circuit 60,
If necessary, the image is rotated by rearranging the pixels.

As described above, the color signal subjected to the color correction and the color selection signal subjected to the pixel rearrangement processing are input to the expansion circuit 58, where they are expanded into multi-valued image data in pixel units. You.

The color signal stored in the image memory 50 is input to a color difference calculation circuit 61, where the color difference between a plurality of color data included in the color signal is calculated for each of the RGB colors. The density determination circuit 62 determines the density of a plurality of color data included in the color signal based on the result of the color difference calculation circuit 61 and stores the result in the density memory 63. The color memory 63 also stores the color selection signal output from the image rotation circuit 60.

The characteristic point judging circuit 64 is based on the shading result of the color data used in the predetermined image area stored in the shading memory 63 and the selection number of the color data used for each pixel in the predetermined image area. Next, extraction of a feature point and determination of an image area are performed. Then, an instruction is issued to select an appropriate halftone process according to the result.

The halftone reproduction processing circuit 59 performs a plurality of halftone processes (halftone dithering, simple dithering, parallel line processing, etc.) on the multivalued image data expanded by the expansion unit 58 in parallel. Then, in accordance with the instruction of the feature point determination circuit 64, an appropriate result is selected from a plurality of halftone processing results, and the halftone is reproduced and output based on the selected result.

In the first embodiment of the present invention described above,
The case has been described in which, as the color signal of the compressed image data, a signal in which a color in a predetermined image area is approximated to a plurality of colors by an operation in consideration of a color space.

However, the compressed image data used in the present invention includes, for each predetermined image area, a color signal including specifying information for specifying at least one color used to represent the predetermined image, and a color signal in the predetermined image area. And a color selection signal including selection information for selecting the specific information from the color signals.

Hereinafter, as a second embodiment of the present invention, a case will be described in which the color signal of the compressed image data approximates a color in a predetermined image area to a plurality of colors using a color pallet table.

First, the compressed image data used in this embodiment will be described.

FIG. 16 is a view for explaining an example of the configuration of compressed image data when colors in a predetermined image area are approximated to a plurality of colors using a color palette table. Here, 22c shows the data structure of the color signal, and 22d shows the data structure of the color selection signal.

In the example shown in FIG. 16, the color signal approximates the colors used in the predetermined image area to two colors of color 0 and color 1 using a color pallet table.

Specifically, as shown in FIG. 17, two similar colors are selected from a color pallet table by referring to the color data of each pixel in a predetermined image area. And selected 2
Information (pallet number) for specifying a color is arranged in a predetermined order and is generated as a color signal. As shown in FIG.
If the number of colors on the color palette table is 256 colors,
The pallet number can be represented by 8 bits. Therefore, the color signal has a total of 16 bits as shown in FIG.

The color selection signal is constituted by, for each pixel in the predetermined image area, information (number) for specifying a palette number indicating an approximate color of the pixel, arranged in pixel order. As shown in FIG. 16, when the color signal is composed of two colors, color 0 and color 1, the color selection signal has one bit per pixel.

Therefore, according to the compressed image data shown in FIG. 16, 4 × 4 pixel bitmap image data (8 bits for each color of RGB, 24 bits per pixel, 384 bits in total) is converted into 16 bits of color signals and color selection. Signal 16
It can be compressed to a total of 32 bits.

Next, the configuration of the present embodiment will be described.

FIG. 18 is a block diagram showing a configuration of the printer controller 11a which is a main part of the present embodiment. The other configuration is the same as that of the first embodiment shown in FIG.

The printer controller 11a of this embodiment
Is different from the printer controller 11 shown in FIG.
As shown in FIG. 18, an image processing unit 16a is used instead of the image processing unit 16, and an expansion unit 14a is used instead of the expansion unit 14.

The image processing section 16a has a color pallet table calculation section 166, a color selection signal calculation section 162, a feature point determination section 167, and an image processing selection section 165. Here, the color selection signal calculation unit 162 and the image processing selection unit 1
65 is the same as that used in the first embodiment.

The color pallet table calculation unit 166 performs color conversion from RGB to YMCK or color conversion on a color pallet table prepared in advance in the memory (the same table as the color pallet table used when compressing image data). Adjustment or color correction such as halftone correction is performed. In the above-described first embodiment, the color correction is performed on the color signal. However, the color signal used in the present embodiment is configured by a pallet number on a color pallet table of each of a plurality of approximate colors. That is, unlike the color signal of the first embodiment, the color signal itself does not have color data. For this reason,
Color correction cannot be performed directly on color signals. Therefore, in the present embodiment, color correction is performed on the color pallet table. Note that the content of the color correction itself is basically the same as that of the first embodiment.

The feature point judging section 167 is provided with an expanding section 1 described later.
A feature point such as an edge is determined based on the multivalued image data in pixel units expanded in 4a. This processing is basically the same as the edge determination described with reference to FIGS. 22 to 25 in the related art.

The decompression unit 14a receives the color signal sent from the image memory 13, the color selection signal sent from the color selection signal operation unit 162, and the color pallet table operation unit 166.
Based on the color pallet table that has been subjected to the color correction, multi-valued image data is generated in pixel units.

FIG. 19 is a block diagram showing the configuration of the extension section 14a shown in FIG. Here, when the data shown in FIG. 16 is used as the compressed image data, that is, when the color signal includes two color pallet numbers, the decompression unit 1
4A shows an example of the configuration.

In the example shown in FIG. 19A, the image memory 1
3 and the color selection signal calculation unit 162
And the color selection signal sent from the storage unit 142 to the separation storage unit 142 via the buffer 141. The separation storage unit 142
Two color pallet numbers are obtained from the color signals, and are sequentially stored in the memories 142a and 142b. In addition, data of each pixel (a number for selecting a color pallet number from a color signal) included in the color selection signal is developed into a bitmap in pixel order and stored in the memory 142c.

Next, the selector 143 selects the memory 14
The data of each pixel is sequentially read from 2c, and the data (color pallet number) stored in one of the memories 142a and 142b is read according to the number indicated by the read data. Then, in the conversion unit 144,
The color palette table 144a, which has been subjected to the color correction by the color palette table calculation unit 166, is referred to, and the color palette number sent from the selector 143 is converted into the corresponding color data. Thereby, the compressed image data is expanded into multi-valued image data in pixel units.

In the example shown in FIG. 19B, the color selection signal sent from the color selection signal
1 and the color signal sent from the image memory 13 to the conversion unit 144 via the buffer 141. The conversion unit 144 acquires a color pallet number from the color signal. The acquired color pallet number is converted into color data with reference to the color pallet table 144 a on which the color correction has been performed by the color pallet table calculation unit 166, and is sequentially transmitted to the separation storage unit 142.

The separation storage section 142 acquires the color data sent from the conversion section 144 and sequentially stores the color data.
d, 142e. In addition, the data of each pixel included in the color selection signal sent from the buffer 141 is developed on a map and stored in the memory 142c.

Next, the selector 143 sets the memory 14
Data of each pixel is sequentially read from 2c, and data (color data) stored in one of the memory 142d and the memory 142 is read according to the number indicated by the read data. Thereby, the compressed image data is expanded into multi-valued image data in pixel units.

According to the second embodiment of the present invention, the color correction is performed not on the color signal read from the image memory 13 but on the color signal.
This is performed for a color pallet table prepared in advance (the same table as the color pallet table used for compressing the image data). Therefore, it is possible to execute the color correction processing in advance.

Also, in this embodiment, as in the first embodiment, the pixel rearrangement processing such as image rotation can be performed directly on the color selection signal. Capacity and the like can be reduced.

In the above embodiment, a color pallet table (a color pallet table in which each color data included in the table is RGB) used when the image data is compressed by the computer is prepared in the printer controller in advance. The description has been given of the case where each color data included in this table is converted from RGB data to CMYK data by the color pallet table calculation unit 166. However, the color pallet table prepared in advance in the printer controller is not limited to this. A color pallet table obtained by converting each color data included in the color pallet table used when the image data is compressed by the computer into color data corresponding to the characteristics of the printer engine may be prepared in the printer controller in advance. . For example, when each color data included in the color pallet table used when compressing the image data by the computer is composed of RGB, the color pallet table obtained by color-converting each of the color data into CMYK is sent to the printer controller side. It may be prepared in advance. In this case, the color conversion processing in the color pallet table calculation unit 166 becomes unnecessary.

In the first and second embodiments, the case where the present invention is applied to a printer has been described, but the present invention is not limited to this. As described above, the present invention can be applied to various image output devices such as a facsimile and a monitor in addition to a printer.

As an example, a case where the present invention is applied to a display controller will be described. FIG. 20 is a diagram showing a circuit configuration of a display controller 70 to which the present invention is applied.

In FIG. 20, the CPU in the computer
80 compresses the multivalued image data in pixel units into compressed image data composed of a color signal and a color selection signal in the manner described in each of the above embodiments, and stores this in the memory 81.

The memory address generation circuit 75 generates an address of data to be read from the memory 81 in accordance with the scan address generated by the scan address generation circuit 77 based on the clock output from the oscillator 78. In response, the compressed image data is sequentially read from the memory 81.

The compressed image data sequentially read from the memory 81 is input to the image processing circuit 72 via the register 71. When the color signal of the compressed image data is composed of color data of a plurality of colors approximated by an operation using a color space, the color signal is converted to the color signal in the manner described in the first embodiment. Make corrections. However, the color conversion processing from RGB to YMCK is not performed. When the color signal is composed of the color pallet numbers on the color pallet table of a plurality of colors, the color correction is performed on the color pallet table prepared in advance as described in the second embodiment. However, in this case as well, the color conversion processing from RGB to YMCK is not performed, and the image processing circuit 72 responds to the color selection signal of the compressed image data by using pixel rotation, enlargement / reduction, etc. Processing with sorting,
Perform as needed.

The color signal and the color selection signal output from the image processing circuit 72 are expanded by the expansion circuit 73 into multi-valued image data in pixel units in the manner described in each of the above embodiments. It is converted to an analog signal by the A converter. Then, the signal is output to the display 82 by the synchronization circuit 76 together with the synchronization signal generated based on the scan address generated by the scan address generation circuit 77.

[0156]

As described above, according to the present invention,
The capacity of the memory required for image processing can be reduced, and the bus width for transferring image data can be reduced, so that the circuit scale can be reduced.

[Brief description of the drawings]

FIG. 1 is a schematic block diagram illustrating a printer according to a first embodiment of the invention.

FIG. 2 is a diagram for describing a configuration example of compressed image data in a case where colors in a predetermined image area are approximated to a plurality of colors by a calculation in consideration of a color space.

FIG. 3 is a diagram for explaining a generation process of a color signal of the compressed image data shown in FIG. 2;

FIG. 4 is a configuration block diagram of the printer controller 11 shown in FIG.

FIG. 5 is a block diagram illustrating a configuration of a color signal calculation unit 161 illustrated in FIG. 4;

6 is a schematic block diagram of a color determination unit 163 and a feature point determination unit 164 shown in FIG.

FIG. 7 is a diagram illustrating a color determination unit 163 and a feature point determination unit 16 illustrated in FIG.
FIG. 6 is a diagram for explaining a flow of processing in No. 4;

8 is a diagram showing a more detailed processing flow of a color determination unit 163 shown in FIG.

FIG. 9 is a diagram illustrating a color determination unit 163 and a feature point determination unit 16 illustrated in FIG.
FIG. 6 is a diagram for explaining a flow of processing in No. 4;

10 is a diagram illustrating a color difference calculation unit 16 of the color determination unit 163 shown in FIG.
It is a figure for explaining the flow of more detailed processing in 3a.

FIG. 11 is a diagram illustrating a density determining unit 16 of the color determining unit 163 illustrated in FIG. 9;
FIG. 4 is a diagram for explaining a more detailed processing flow in 3b.

FIG. 12 is a diagram for explaining another shading determination method when four color data are included in a color signal.

FIG. 13 is a block diagram showing a configuration of a halftone processing unit 17 shown in FIG.

FIG. 14 is a view for explaining a modification of the first embodiment of the present invention shown in FIG. 1;

FIG. 15 is a diagram illustrating a circuit configuration of a printer controller to which the first embodiment of the present invention has been applied.

FIG. 16 is a diagram for describing a configuration example of compressed image data when colors in a predetermined image area are approximated to a plurality of colors using a color pallet table.

FIG. 17 is a diagram for explaining a generation process of a color signal of the compressed image data shown in FIG. 16;

FIG. 18 is a configuration block diagram of a printer controller 11a which is a main part of the second embodiment of the present invention.

FIG. 19 is a block diagram illustrating a configuration of an extension unit 14a illustrated in FIG. 18;

FIG. 20 is a diagram showing a circuit configuration of a display controller 70 to which the present invention is applied.

FIG. 21 is a schematic block diagram for explaining a conventional printer.

FIG. 22 is a diagram for explaining the flow of edge determination processing in a conventional image processing apparatus.

FIG. 23 is a diagram showing a memory for storing bitmap image data in a conventional image processing apparatus.

FIG. 24 is a diagram for explaining edge determination processing in a conventional image processing apparatus.

FIG. 25 is a diagram for explaining edge determination processing in a conventional image processing apparatus.

DESCRIPTION OF SYMBOLS 1 printer 2 computer 11 printer controller 12 printer engine 13, 18, 21, 23, 50 image memory 14, 14a decompression unit 16, 16a image processing unit 17 halftone processing unit 22 compression unit 51 color correction circuit 52 , 54, 55, 55, 57, 81, 142a-14
2e, 144, 161d to 161f Memory 53 Color conversion circuit 56 Gamma correction circuit 58, 73 Decompression circuit 59 Halftone reproduction processing circuit 60 Image rotation circuit 61 Color difference calculation circuit 62 Shading circuit 63 Shading memory 64 Feature point judgment circuit 71 Register 72 Image processing circuit 74 A / D conversion circuit 75 Memory address generation circuit 76 Synchronization circuit 77 Scan address generation circuit 76 Transmitter 80 CPU 82 Display 141 Buffer 142 Separation storage unit 161 Color signal calculation unit 161a Color correction unit 161b Color conversion unit 161c Intermediate Length correction section 162 Color selection signal calculation section 163 Color determination section 163a Color difference calculation section 163b Gray level determination section 164,167 Feature point determination section 164a Gray level binary data memory 164b Feature point extraction section 165 Image processing selection section 166 Color palette selection section Table operation section 171 Halftone processing A section 172 Halftone processing B section 173 Halftone processing C section 174 Smoothing processing section 175, 143 Selector 176 Halftone reproduction section

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tamura et al. 1-1-1, Higashitaga-cho, Hitachi City, Ibaraki Prefecture Inside the Electrification Equipment Division, Hitachi, Ltd. (72) Inventor Naoyuki Urata 810 Shimoimaizumi, Ebina City, Kanagawa Prefecture Hitachi, Ltd. Office Systems Division (72) Inventor Tadashi Okada 810, Shimoimaizumi, Ebina-shi, Kanagawa Prefecture Hitachi Systems Office Systems Division

Claims (19)

[Claims] 1. An image processing apparatus, comprising: for each predetermined image area, a color signal including identification information for identifying at least one color used to represent the predetermined image; For a pixel, a color selection signal including selection information for selecting the specific information from the color signal, an image processing unit that performs image processing on compressed image data, and an image processing unit. According to the selection information of each pixel in the predetermined image area included in the color selection signal of the compressed image data, the compressed image data that has been subjected to the image processing is assigned to each of the pixels. Decompressing means for decompressing multi-valued image data in pixel units by adding color data specified by specific information included in the color signal of the data. . 2. The image processing apparatus according to claim 1, wherein said image processing means performs processing on said color signal and processing on said color selection signal in parallel. 3. An image processing apparatus according to claim 1, wherein said image processing means rotates or scales up or down the image by changing the arrangement of selection information of each pixel included in said color selection signal. An image processing apparatus, comprising: a color selection signal processing unit that performs the following. 4. The image processing apparatus according to claim 1, wherein the color signal has color data as the specific information, and the image processing unit performs a process on the color data included in the color signal. An image processing apparatus having color signal processing means for performing color correction processing. 5. The image processing apparatus according to claim 1, wherein the color signal is a color pallet number for specifying color data from a color pallet table having a plurality of color data as the specific information. An image processing apparatus comprising: a color pallet table processing unit configured to perform a color correction process on color data included in the color pallet table. 6. The image processing apparatus according to claim 4, wherein the color correction processing is a color conversion. 7. The image processing apparatus according to claim 4, wherein said color correction processing is gamma correction. 8. The image processing apparatus according to claim 1, wherein the color shading between the target pixel and pixels surrounding the target pixel is converted into pixel-based multi-valued image data expanded by the expansion unit. A multi-valued image data expanded by the decompression unit, which has been subjected to halftone processing according to the judgment result of the characteristic judgment means, An image processing apparatus, further comprising: a halftone processing unit. 9. The image processing apparatus according to claim 1, wherein the color signal has color data as the specific information, and a color density between a target pixel and pixels around the target pixel. By examining the color data included in the color signal and the selection information included in the color selection signal,
A characteristic determination unit that determines the characteristic of the target pixel; a halftone processing unit that outputs multi-valued image data expanded by the expansion unit, which has been subjected to halftone processing according to the determination result of the characteristic determination unit; An image processing apparatus, further comprising: 10. The image processing apparatus according to claim 8, wherein said halftone reproducing means performs different halftone processing on multi-valued image data in pixel units expanded by said expansion unit. An image, comprising: two halftone processing units; and a selector that selects one of the at least two halftone processing units in accordance with a result of the determination by the feature point determination unit. Processing equipment. 11. The image processing apparatus according to claim 10, wherein the feature determination unit determines that the target pixel is a feature point when the color of the target pixel is darker than pixels surrounding the target pixel. The image processing apparatus, wherein the selector switches a halftone processing unit to be selected according to whether or not the target pixel is determined to be a feature point. 12. The image processing apparatus according to claim 11, wherein one of said at least two halftone processing means is a smoothing processing means, and said selector determines that a target pixel is a feature point. If done,
An image processing apparatus for selecting multivalued image data for the target pixel subjected to the smoothing processing by the smoothing processing means. 13. A printer, comprising: an image forming unit that forms a printed image; and an image processing unit that outputs a signal for forming a printed image to the image forming unit, wherein the image processing unit comprises: For each predetermined image area, a color signal including specific information for specifying at least one color used to represent the predetermined image, and, for each pixel in the predetermined image area, the specific information from the color signals. Storage means for storing compressed image data comprising a color selection signal including selection information for selecting the image data; image processing means for reading out the compressed image data stored in the storage means and performing image processing; The compressed image data that has been subjected to the image processing by the image processing means is assigned to each pixel according to the selection information of each pixel in a predetermined image area included in the color selection signal of the compressed image data. Expansion means for expanding the multivalued image data in pixel units by adding color data specified by the specific information included in the color signal of the compressed image data selected by the expansion means; Output means for outputting a signal for forming a printed image to the image forming unit in accordance with the value image data. 14. The printer according to claim 13, wherein said image processing means performs rotation or enlargement / reduction of the image by changing the arrangement of selection information of each pixel included in said color selection signal. A printer comprising color selection signal processing means. 15. The printer according to claim 13, wherein said color signal has color data consisting of RGB data as said specific information, and said image processing means includes a color data included in said color signal. A color conversion means for converting image data from RGB data into YMCK data. 16. The printer according to claim 13, wherein said color signal has color data as said specific information, and said image processing means converts the color data contained in said color signal into said image data. A printer comprising gamma correction means for performing gamma correction so as to match characteristics of a forming unit. 17. The printer according to claim 13, wherein the color signal has color data as the specific information, and determines color shading between a target pixel and pixels around the target pixel. By examining based on color data included in the color signal and selection information included in the color selection signal,
The image processing apparatus further includes a feature determination unit that determines a feature of the target pixel, wherein the output unit performs halftone processing according to a determination result of the feature determination unit, and is multi-valued image data expanded by the expansion unit. A printer for generating a signal for forming a printed image based on the printer. 18. An image processing method for decompressing and outputting compressed image data, wherein the image processing is performed on the compressed image data prior to the decompression processing of the compressed image data. . 19. The image processing method according to claim 18, wherein the compressed image data includes, for each predetermined image area, specific information for specifying at least one color used to represent the predetermined image. A color signal, and a color selection signal including selection information for selecting the specific information from the color signal for each pixel in the predetermined image area, wherein the decompression processing is performed by image processing. In accordance with the selection information of each pixel in the predetermined image area included in the color selection signal of the compressed image data, the compressed image data is added to the color signal of the compressed image data selected by the selection information. An image processing method characterized in that color data specified by specific information included is added to expand multi-valued image data in pixel units.