JP2007174080A - Image log generating device, image forming apparatus, image log generating method, and program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image log generating device capable of generating an image log easy to read both of characters/pictures, using a simple configuration. <P>SOLUTION: A control portion 10 of an image log generating device directs a region extraction portion 104 to extract a text area representing characters and an image area representing pictures from an image data, and instructs an area determination portion 105 to determine a ratio of each region. Then, the control portion 10 controls a JPEG compression portion 106 to perform compression processing when the image data comprises mainly pictures, and controls a run length compression portion 107 to perform compression processing when the image data comprises mainly characters. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a technique for efficiently generating an image log that is easy for a user to read.

  Some copiers and facsimile machines have a function of accumulating and storing document images that have been previously processed (copy processing / facsimile transmission / reception processing) as image logs. Since an image log has a large storage capacity, compressed image data such as a thumbnail image is generally used. At this time, if the image data is extremely compressed, it becomes difficult for the user to read. Therefore, it is required to perform data compression that ensures the user's readability while appropriately reducing the data amount.

Under such a background, in the technique described in Patent Document 1, the character area and the other area are separated, and a suitable color reduction process (that is, a compression process) is performed on each area, so that the legibility is improved. We are trying to improve. In the technique described in Patent Document 2, whether the image data is a document or a photograph is identified, and each of them is reduced (that is, compressed) by a different method.
JP 2003-224734 A Japanese Patent Laid-Open No. 2004-32078

  However, since the technique described in Patent Document 1 performs image area determination of image data and performs a plurality of compression processes on the same image data, the process is complicated. In copying machines and facsimile machines, the main processing is copy processing and facsimile transmission / reception processing, and the processing for accumulating image logs is only a secondary processing. Therefore, it cannot be said that it is preferable to allocate a lot of resources to the process of accumulating image logs. In addition, the technique described in Patent Document 2 may reduce legibility in image data in which characters and photographs are mixed.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a technique for generating an image log that enables easy reading of both characters and pictures using a simple configuration. There is to do.

In order to achieve the above object, the present invention provides an extraction means for extracting a text area representing a character and an image area representing a picture from input image data, and the text area and the image area extracted by the extraction means. When the ratio of the image area to the text area is equal to or greater than a predetermined threshold, the input image data is compressed by the first compression method, while the ratio is less than the threshold. In some cases, the input image data is compressed by a second compression method having a compression rate lower than that of the first compression method, and the image data compressed by the compression means is output to a storage device. An image log generation device comprising output means for performing the operation is provided.
According to this image log generation device, since compression processing can be performed with a compression method according to the ratio of the text area to the image area, compression processing suitable for each image data can be performed without using a complicated configuration. Can do.

  In the image log generation device, the extraction unit includes a conversion unit that converts the input image data into image data having only a luminance component, and uses the luminance component of the image data converted by the conversion unit. It is more preferable to extract the text area and the image area. In this way, the data size can be further reduced without degrading the legibility of the image data.

  The present invention also provides the above-described image log generation apparatus, image forming means for forming an image representing input image data on a recording material, and image data representing an image formed by the image forming means to the image log. The image forming apparatus may include an input unit that inputs to the extraction unit of the generation device. Examples of the image forming apparatus include a printer, a copier, and a multifunction machine.

  Further, the present invention provides an extraction step of extracting a text region representing characters and an image region representing a pattern from the input image data, and extracting in the extraction step when compared with the text region extracted in the extraction step. The input image data is compressed by the first compression method when the ratio of the image area is equal to or greater than a predetermined threshold, and when the ratio is less than the threshold, the input A compression step of compressing the image data by a second compression method having a compression rate lower than that of the first compression method; and an output step of outputting the image data compressed in the compression step to a storage device. As an image log generation method.

  Further, the present invention provides the computer with an extraction process for extracting a text area representing characters and an image area representing a pattern from input image data, and the extraction when compared with the text area extracted in the extraction process When the ratio of the image area extracted in the process is equal to or greater than a predetermined threshold, the input image data is compressed by the first compression method, while when the ratio is less than the threshold, A compression process for compressing input image data by a second compression method having a compression rate lower than that of the first compression method, and an output process for outputting the image data compressed in the compression process to a storage device are executed. It can also be specified as a program to be executed.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Here, as an embodiment of the present invention, a copying machine including an image log generation device will be described. However, the following description is not intended to limit the implementation of the present invention to such an embodiment.

[1. Constitution]
FIG. 1 is a block diagram showing a configuration of a copying machine CP according to an embodiment of the present invention. As shown in the figure, the copier CP includes a control unit 10, an operation unit 20, a communication unit 30, an image input unit 40, an image output unit 50, and a log storage unit 60.

  The control unit 10 includes a CPU (Central Processing Unit), an ASIC (Application Specific Integrated Circuit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like, and the CPU executes a program stored in the ROM. To control the operation of each part of the copier CP. Note that the ASIC performs various image processing on the input image data. The operation unit 20 is an input device including a touch panel display and various buttons, and receives an input instruction from a user. This input instruction is supplied to the control unit 10. The communication unit 30 is an input / output interface for exchanging data via an external device or a network.

  The image input unit 40 has a scanner function, and generates image data indicating a document by optically reading the document. This image data is image data composed of 8-bit color components of red (R), green (G), and blue (B), that is, RGB color system image data. 10 is supplied. The image output unit 50 is an electrophotographic printer, and forms a toner image corresponding to image data on a recording sheet. The log storage unit 60 is a large-capacity storage device having an HDD (Hard Disk Drive), and stores and stores image data used by the image output unit 50 for image formation as a log. Note that the image data stored in the log storage unit 60 is not the image data itself used for image formation, but image data that has been subjected to compression processing described later.

  With this configuration, the copying machine CP forms an image on a recording sheet based on the image data generated by the image input unit 40. At the same time as the image formation, the control unit 10 performs compression processing on the image data used at this time and stores it in the log storage unit 60. That is, the control unit 10 also has a function as an image log generation device.

  Here, FIG. 2 is a functional block diagram showing functions realized by the control unit 10. As shown in the figure, the functional configuration of the control unit 10 includes a color conversion unit 101, a color determination unit 102, a data conversion unit 103, a region extraction unit 104, a region determination unit 105, and a JPEG compression unit 106. And the run-length compression unit 107 and the output unit 108.

  The color conversion unit 101 performs an operation for converting the color system of image data. Specifically, the color conversion unit 101 converts RGB color system image data (8 bits) into YCrCb color system image data (8 bits). Here, the YCrCb color system image data is image data including a luminance component (Y) and color difference components (Cr, Cb), and color conversion from the RGB color system to the YCrCb color system is well known. Done by an algorithm.

  The color determination unit 102 determines whether the image data is color image data. Specifically, the color determination unit 102 determines whether or not the color image data is based on the absolute value of the color difference component included in the YCrCb color system image data. If the absolute value of the color difference component is approximately “0”, the color determination unit 102 determines that the image data is monochrome image data (monochrome image data), and otherwise, color image data ( Color image data).

  The data conversion unit 103 performs an operation for converting color image data into monochrome image data. Specifically, the data conversion unit 103 obtains monochrome image data by converting the color difference component of the image data to 0. The area extraction unit 104 analyzes the monochrome image data and extracts a “text area” representing characters and an “image area” representing pictures. This extraction process is performed using a known edge determination process or spatial frequency analysis.

  The area determination unit 105 calculates the ratio of the text area to the image area in the entire image data, and determines whether the image data is character-based image data or design-based image data. Specifically, the area determination unit 105 determines that the image data is mainly a pattern when the ratio of the image area to the text area is equal to or greater than a predetermined threshold, and the ratio is less than the above-described threshold. The image data is determined to be mainly text. Note that the threshold value is arbitrary, but the simplest method is that the image is mainly composed if the image area is larger than the text area, and the text is mainly composed if the text area is larger than the image area. It is.

  The JPEG compression unit 106 performs compression processing on image data by a well-known JPEG (Joint Photographic Experts Group) method. The image data that is compressed by the JPEG compression unit 106 is image data that has been determined by the region determination unit 105 to be mainly a pattern. The run length compression unit 107 performs a compression process based on a known run length method on the image data. The image data that is compressed by the run-length compression unit 107 is image data that has been determined by the region determination unit 105 to be mainly a character. The compression rate of the compression process in the JPEG compression unit 106 is configured to be higher than the compression rate of the compression process in the run-length compression unit 107. The compression processing by the JPEG method is suitable for use with multi-gradation image data, and image data mainly composed of a pattern can be favorably compressed. On the other hand, the compression process based on the run length method is suitable for use on image data containing a large number of characters, line drawings, and the like, and can compress image data mainly composed of characters.

  The output unit 108 writes the image data compressed by the JPEG compression unit 106 or the run length compression unit 107 into the log storage unit 60 as an image log. The output unit 108 also has a function of sequentially deleting the image data stored in the log storage unit 60 from the first stored when the log storage unit 60 has no free space and image data cannot be written. Have.

[2. Operation]
With the above configuration, the copying machine CP performs processing for storing image data used for image formation as an image log while reading a document and forming an image. At this time, the copying machine CP analyzes the image data and performs processing according to the attribute of each image data. Hereinafter, specific operations executed by the copying machine CP will be described.

  FIG. 3 is a flowchart showing processing executed by the copying machine CP when creating an image log. Describing along the drawing, first, the control unit 10 of the copier CP converts the RGB color system image data used for image formation into YCbCr color system image data (step S1). Thereafter, the control unit 10 determines whether the image data is color image data or monochrome image data by referring to the color difference component of the image data (step S2). When the image data is color image data (step S2; YES), the control unit 10 converts the image data into monochrome image data by setting the color difference component of the image data to “0” (step S2; YES). Step S3). On the other hand, if the image data is monochrome image data (step S2; NO), the control unit 10 does not need to perform the process of step S3, so this process is skipped. In the subsequent processing, the control unit 10 handles the image data as data of only the luminance component. That is, at this time, the data amount per pixel decreases from 24 bits (3 × 8 bits) to 8 bits (1 × 8 bits).

  Subsequently, the control unit 10 extracts a text area from the image data including only the luminance component (step S4), and then extracts an image area (step S5). After extracting these areas, the control unit 10 compares the area ratio between the text area and the image area to determine whether the image data is character-oriented image data or design-oriented image data. (Step S6). If it is determined that the image data is mainly a pattern (step S6; YES), the control unit 10 compresses the image data using the JPEG method (step S7). On the other hand, when it is determined that the image data is mainly text (step S6; NO), the control unit 10 compresses the image data using the run-length method (step S8).

  When the image data compression processing is performed, the control unit 10 calculates the data capacity of the image data (step S9). Subsequently, the control unit 10 refers to the free capacity of the log storage unit 60 and compares the free capacity with the data capacity calculated in step S9 to determine whether or not compressed image data can be written. (Step S10). If the free capacity of the log storage unit 60 is greater than or equal to the data capacity calculated in step S9 (step S10; YES), the control unit 10 writes the compressed image data to the log storage unit 60 (step S12), while the log If the free capacity of the storage unit 60 is smaller than the data capacity calculated in step S9 (step S10; NO), the control unit 10 deletes the image data stored in the log storage unit 60 from the oldest one (step S11). The determination process in step S10 is repeated until the image data can be written.

  The process in which the copying machine CP stores the image log is as described above. By performing such processing, the copying machine CP can maintain the legibility of the image data stored in the log storage unit 60 while maintaining a high compression rate. Further, as described above, the image data stored in the log storage unit 60 is image data having only a luminance component. For this reason, the image data can be reduced in data capacity while having good visibility by human eyes.

[3. Modified example]
In addition, this invention is not limited only to embodiment mentioned above, It is possible to implement in a various aspect. In the present invention, for example, the following modifications can be applied to the above-described embodiment. These modifications can be combined as appropriate.

  In the above-described embodiment, in order to easily understand the contents of the present invention, it has been described that the control unit 10 performs the process of determining whether the image data is color image data (step S2). Processing is not always necessary. For example, if the control unit 10 performs a process of removing the color difference component from the image data, it is not necessary to determine whether the image data is color image data or monochrome image data in the first place. Therefore, such a process may be performed instead of the processes in steps S2 and S3 described above.

  In the above-described embodiment, the JPEG method and the run length method are shown as the compression method. However, the compression method is not limited to these, and an appropriate method may be used. In the above-described embodiment, only two types of compression processing can be performed on image data. However, the compression method can be appropriately selected from three or more types of compression according to the ratio of the text area to the image area. It may be.

  Further, the above embodiment has been described with reference to the copying machine CP. However, the present invention is not limited to the copying machine. For example, the image forming apparatus (printer), the image reading apparatus (scanner), the facsimile apparatus, and the like. It is also possible to implement by a so-called multi-function machine having some of the functions. In short, the present invention can be applied to all apparatuses that perform some processing using image data.

1 is a block diagram illustrating a configuration of a copier that is an embodiment of the present invention. FIG. 3 is a functional block diagram illustrating functions realized by a control unit of the copier. FIG. 3 is a flowchart showing processing executed by the copying machine when creating an image log.

Explanation of symbols

CP: MFP, 10: control unit, 101: color conversion unit, 102 ... color determination unit, 103 ... data conversion unit, 104 ... area extraction unit, 105 ... area determination unit, 106 ... JPEG compression unit, 107 ... run length Compression unit 108 ... Output unit 20 ... Operation unit 30 ... Communication unit 40 ... Image input unit 50 ... Image output unit 60 ... Log storage unit

Claims (5)

Extraction means for extracting a text area representing characters and an image area representing a pattern from the input image data;
The areas of the text region and the image region extracted by the extracting unit are compared, and if the ratio of the image region to the text region is equal to or greater than a predetermined threshold, the input image data is converted to the first compression method. On the other hand, if the ratio is less than the threshold value, the compression means for compressing the input image data with a second compression method having a compression rate lower than that of the first compression method;
An image log generation apparatus comprising: output means for outputting the image data compressed by the compression means to a storage device. The extraction means includes
Conversion means for converting the input image data into image data having only a luminance component;
The image log generation device according to claim 1, wherein the text region and the image region are extracted using a luminance component of the image data converted by the conversion unit. An image log generation device according to claim 1;
Image forming means for forming an image representing the input image data on a recording material;
An image forming apparatus comprising: input means for inputting image data representing an image formed by the image forming means to the extracting means of the image log generating apparatus. An extraction step for extracting a text area representing characters and an image area representing a pattern from the input image data;
When the ratio of the image area extracted in the extraction step when compared with the text area extracted in the extraction step is equal to or greater than a predetermined threshold, the input image data is compressed by the first compression method. On the other hand, if the ratio is less than the threshold value, a compression step of compressing the input image data with a second compression method having a compression rate lower than that of the first compression method;
An image log generation method comprising: an output step of outputting the image data compressed in the compression step to a storage device. On the computer,
An extraction process for extracting a text area representing characters and an image area representing a pattern from input image data;
When the ratio of the image area extracted in the extraction process when compared with the text area extracted in the extraction process is equal to or greater than a predetermined threshold, the input image data is compressed by the first compression method. On the other hand, if the ratio is less than the threshold, the input image data is compressed by a second compression method having a compression rate lower than that of the first compression method;
A program for executing an output process for outputting the image data compressed in the compression process to a storage device.

Images