JP2006157119A - Color image processing apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a color image processing apparatus capable of compressing image data at a suitable compression rate, according to the size of the acquired image data. <P>SOLUTION: The apparatus is provided with a reading unit 102 for reading an image at a certain resolution to acquire image data, a correspondence table 132 for correlating image data with a thinning rate for each resolution and storing the thinning rate, a selection unit 134 for referring to the correspondence table 132 to select a ratio, corresponding to the resolution used for reading by the reading unit 102, and a YCbCr conversion unit 112 for thinning the image data at the ratio selected by the selection unit 134. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a color image processing apparatus, and more particularly to a color image processing apparatus that compresses read image data.

  As a color image processing apparatus, for example, a copy, a scanner, a printer, a facsimile, and a complex machine of these are conventionally known. In recent years, such a color image processing apparatus can be connected to a network with the progress of network technology. Therefore, not only printing out the image data obtained using the scan function, but also transferring it to a shared folder via the network, sending it attached to an e-mail, or uploading it to an FTP server. (For example, Patent Document 1).

Such an apparatus generates RGB data using a scan function. This RGB data is converted into, for example, a JPEG format file or the like for handling on the network. In this way, when RGB data is to be compressed and encoded by the JPEG method, the RGB data is converted into YCbCr data (luminance color difference signal) and then compressed and encoded in units of blocks (for example, 64 pixels of 8 × 8). . Thereby, the amount of calculation can be reduced and the compression effect can be enhanced.
JP 2000-50000 A

  However, when communicating image data via a network in this way, the image data read at high resolution is large in size, so if the capacity of the storage area of the transfer buffer is not sufficient, the buffer overflows or transfers Inconveniences such as taking time may occur.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a color image processing apparatus capable of compressing at an appropriate compression rate in accordance with the size of acquired image data. .

According to the present invention, an acquisition unit that reads an image at a certain resolution and acquires image data;
A correspondence table for storing the ratio of thinning out the image data for each resolution in association with each other;
A selection unit that refers to the correspondence table and selects the ratio corresponding to the resolution used by the acquisition unit for reading;
A sub-sampling unit that thins out the image data at the ratio selected by the selection unit;
A color image processing apparatus is provided.

  Here, the image data is, for example, image data in RGB format (hereinafter referred to as “RGB data”). The ratio used in the sub-sampling unit is a sub-sampling ratio, such as 4: 4: 4, 4: 2: 2, and 4: 1: 1. The RGB data is converted into YCbCr data by the subsampling unit at the subsampling ratio selected by the selection unit. In the correspondence table, for example, when the reading resolution is 200 dpi or less, the sub-sampling ratio is 4: 4: 4, when the reading resolution is 300 dpi, the sub-sampling ratio is 4: 2: 2, and when the reading resolution is 600 dpi or more, the sub-sampling ratio is 4: 1: 1 is associated.

  According to the present invention, when the RGB data with a low reading resolution, that is, the file size is small, the thinning ratio is set to a small value, and when the RGB data with a high reading resolution, that is, the file size is large, a large thinning ratio is set. Can do. As a result, the image data can be compressed at an appropriate compression rate according to the size of the acquired image data.

  The color image processing apparatus may include a reception unit that receives designation of the resolution, and the selection unit refers to the correspondence table and selects the ratio corresponding to the resolution received by the reception unit. Can do.

  The color image processing apparatus may further include a compression encoding unit that compresses and encodes the data thinned out by the sub-sampling unit. Here, for example, the compression encoding unit compresses and encodes the YCbCr data into the JPEG format. According to this configuration, image data read by a scanner or the like can be compressed to an appropriate size, so that it can be transferred to a shared folder via a network or attached to an email without reducing the communication speed. Or upload to an FTP server. In addition, the required capacity of a storage area such as a transfer buffer can be reduced.

  It should be noted that any combination of the above-described constituent elements and a conversion of the expression of the present invention between a method, an apparatus, a system, a recording medium, a computer program, etc. are also effective as an aspect of the present invention.

  According to the present invention, there is provided a color image processing apparatus that can perform compression at an appropriate compression rate in accordance with the size of acquired image data.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In all the drawings, the same reference numerals are given to the same components, and the description will be omitted as appropriate.

  FIG. 1 is a functional block diagram showing a color image processing apparatus according to an embodiment of the present invention. In the present embodiment, the color image processing apparatus 100 has a scanner function and a copy function. FIG. 1 shows the main elements relevant to the present invention. In FIG. 1, the configuration of parts not related to the essence of the present invention is omitted. For example, the color image processing apparatus 100 has a configuration (not shown) provided in a normal copying machine such as an operation panel or a paper feeding unit. Further, the color image processing apparatus 100 may further include a communication function such as a fax communication function or a network communication function, and a configuration therefor may be provided.

  The color image processing apparatus 100 includes a reading unit 102, a first storage unit 104, a first DMA controller 106, a YCbCr conversion unit 112, a compression encoding unit 114, a second DMA controller 116, and a second DMA controller 116. 2 storage unit 118, control unit 120, resolution receiving unit 130, correspondence table 132, and selection unit 134.

  Here, each component of the color image processing apparatus 100 includes a CPU of any computer, a memory, a program that realizes the components of this figure loaded in the memory, a storage unit such as a hard disk that stores the program, and a network connection It is realized by any combination of hardware and software, with a focus on the interface. It will be understood by those skilled in the art that there are various modifications to the implementation method and apparatus. Each drawing described below shows a functional unit block, not a hardware unit configuration.

  The control unit 120 controls the entire apparatus together with each element of the color image processing apparatus 100 shown in FIG. In FIG. 1, arrows indicating control and data flow between the control unit 120 and each component are omitted.

  The reading unit 102 has a scanner function and reads an original to generate RGB data. Here, the reading unit 102 reads an image for each predetermined line.

  The first storage unit 104 stores the RGB data read by the reading unit 102. The first storage unit 104 is, for example, an SDRAM.

  The first DMA controller 106 transfers the RGB data stored in the first storage unit 104 to the YCbCr conversion unit 112. Note that data transfer from the first storage unit 104 to the YCbCr conversion unit 112 is performed via a general-purpose bus (not shown). In the present embodiment, the control unit 120 controls the timing at which the first DMA controller 106 transfers RGB data to the YCbCr conversion unit 112. In addition, the first DMA controller 106 does not continuously transfer the RGB data stored in the first storage unit 104 to the YCbCr conversion unit 112, but in a predetermined unit, for example, a block unit (here, 8 × 8). Are transferred every 64 pixels).

  The YCbCr converter 112 converts RGB data into color image data (hereinafter referred to as “YCbCr data”) in YCbCr (luminance color difference) format in units of pixels. Here, the YCbCr conversion unit 112 generates YCbCr data by thinning out the RGB data at a sub-sampling ratio selected by the selection unit 134 described later. Examples of the subsampling ratio include 4: 4: 4, 4: 2: 2, 4: 1: 1, and the like. The compression rate from the original data of the finally obtained JPEG file changes depending on the sub-sampling ratio. For example, the smaller the ratio of the color difference signals (4: 1: 1), the higher the compression rate. The compression encoding unit 114 compresses and encodes the YCbCr data in the JPEG format.

  The second DMA controller 116 transfers the JPEG data compressed and encoded by the compression encoding unit 114 to the second storage unit 118. Data transfer from the compression encoding unit 114 to the second storage unit 118 is also performed via the general-purpose bus. The second storage unit 118 is also an SDRAM, for example. In the present embodiment, the control unit 120 controls the timing at which the second DMA controller 116 transfers the JPEG data compression encoded by the compression encoding unit 114 to the second storage unit 118.

  The second storage unit 118 stores JPEG data. The JPEG data stored in the second storage unit 118 is then output to a personal computer or the like via a LAN or USB, for example, by a data output unit (not shown).

  The resolution accepting unit 130 accepts a reading resolution designated by an operation unit (not shown) from the user. In the present embodiment, the resolutions that can be specified are 100, 200, 300, and 600 dpi.

  The correspondence table 132 stores a ratio of thinning out RGB data for each resolution, that is, a sub-sampling ratio in association with each other. FIG. 2 is a diagram illustrating an example of the correspondence table 132. Here, when the resolution is 200 dpi or less (shown as “200 dpi” in the figure), the subsampling ratio is 4: 4: 4, and when the resolution is 300 dpi, the subsampling ratio is 4: 2: 2, and the resolution is 600 dpi or more ( In the drawing, the sub-sampling ratio is 4: 1: 1 when “600 dpi” is indicated.

  Returning to FIG. 1, the selection unit 134 refers to the correspondence table 132 and selects the resolution used by the reading unit 102 for reading, here, the sub-sampling ratio corresponding to the resolution received by the resolution receiving unit 130, and YCbCr The conversion unit 112 is notified.

  In the present embodiment, the YCbCr conversion unit 112 and the compression encoding unit 114 are constructed on, for example, an LSI (Large Scale Integration) dedicated to image compression. The first DMA controller 106 controls input of RGB data to the LSI, and the second DMA controller 116 controls output of a JPEG file from the LSI.

  The operation of the color image processing apparatus 100 configured as described above will be described. FIG. 3 is a flowchart showing an example of the operation of the color image processing apparatus 100 of the present embodiment. In the following description, FIGS. 1 to 3 are used.

  First, when the user sets a document and designates the reading resolution via the operation unit, the resolution receiving unit 130 receives the resolution. When the user presses a start button (not shown), the reading unit 102 starts reading an image with the resolution received by the resolution receiving unit 130 and stores the RGB data in the first storage unit 104. Then, compression encoding processing of the read image data starts.

  First, the control unit 120 opens a JPEG file (S11). Subsequently, the selection unit 134 refers to the correspondence table 132 and selects a sub-sampling ratio according to the resolution received by the resolution reception unit 130. For example, when the resolution is 200 dpi or less (YES in S13), the LSI is instructed to set the subsampling ratio to 4: 4: 4 (S17). When the resolution is 300 dpi (NO in S13 and YES in S15), the LSI is instructed to set the sub-sampling ratio 4: 2: 2 (S19). When the resolution is 600 dpi or more (NO in S13 and NO in S15), the LSI is instructed to set the subsampling ratio to 4: 1: 1 (S21).

  Subsequently, the first DMA controller 106 inputs RGB data from the first storage unit 104 to the LSI (S23). In the LSI, the YCbCr conversion unit 112 thins out the RGB data at the subsampling ratio instructed from the selection unit 134 in steps S17, S19, and S21, and generates YCbCr data.

  That is, for example, RGB data read at a low resolution of 200 dpi or less is converted using a sub-sampling ratio 4: 4: 4, but RGB data read at a high resolution of 600 dpi or more is sub-sampling ratio 4 Converted using 1: 1. This makes it possible to effectively compress large data read at high resolution and reduce the size of the file finally obtained.

  Subsequently, the compression encoding unit 114 compresses and encodes the YCbCr data, and outputs the JPEG data to the second storage unit 118 via the second DMA controller 116 (S25). The control unit 120 writes the JPEG data output from the LSI into the JPEG file (S27).

  Note that the input of RGB data in step S23 is performed in units of blocks, for example. Therefore, the control unit 120 monitors whether or not all RGB data blocks have been compression-encoded (S29), and determines that all blocks have been compression-encoded (YES in S29), the JPEG file is Close (S31). If there is still an uncompressed encoded block (NO in S29), the process returns to step S23 to continue the processing.

  As described above, according to the color image processing apparatus 100 of the present embodiment, RGB data with a low reading resolution, that is, when the file size is small, a small thinning ratio is set, and RGB data with a high reading resolution, that is, a file. When the size is large, a large thinning ratio can be set. As a result, the image data can be compressed at an appropriate compression rate according to the size of the acquired image data.

  In this way, the image data read by a scanner or the like can be compressed to an appropriate size, so that it can be transferred to a shared folder via a network, attached to an email, FTP, etc. without reducing the communication speed. Or upload to a server. In addition, the required capacity of a storage area such as a transfer buffer can be reduced.

  As mentioned above, although embodiment of this invention was described with reference to drawings, these are the illustrations of this invention, Various structures other than the above are also employable.

1 is a functional block diagram showing a color image processing apparatus according to an embodiment of the present invention. It is a figure which shows an example of the correspondence table of the color image processing apparatus of FIG. 3 is a flowchart illustrating an example of the operation of the color image processing apparatus in FIG. 1.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Color image processing apparatus 102 Reading part 112 YCbCr conversion part 114 Compression encoding part 120 Control part 130 Resolution reception part 132 Correspondence table 134 Selection part

Claims (3)

An acquisition unit that reads an image at a certain resolution and acquires image data;
A correspondence table for storing the ratio of thinning out the image data for each resolution in association with each other;
A selection unit that refers to the correspondence table and selects the ratio corresponding to the resolution used by the acquisition unit for reading;
A sub-sampling unit that thins out the image data at the ratio selected by the selection unit;
A color image processing apparatus comprising: The color image processing apparatus according to claim 1,
A reception unit for receiving the resolution designation;
The color image processing apparatus, wherein the selection unit refers to the correspondence table and selects the ratio corresponding to the resolution received by the reception unit. The color image processing apparatus according to claim 1 or 2,
A color image processing apparatus comprising: a compression encoding unit that compresses and encodes the data sampled by the sub-sampling unit.

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