JP2015211238A - Image processing apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image processing apparatus requiring a small buffer capacity at the pre-stage of compression processing, when a compression system is selected depending on the determination results of automatic color determination.SOLUTION: A band color determination unit 3 determined whether each band in a page image is a color band or a monochromatic band, a compression unit 7 executes compression processing of compression system for color band for a color band, and executes compression processing of compression system for monochromatic band for a monochromatic band, based on the determination results in the band color determination unit 3. An extension unit 8 extends a band compressed by the compression system for color band by an extension system corresponding to the compression system for color band, and extends a band compressed by the compression system for monochromatic band by an extension system corresponding to the compression system for monochromatic band.

Description

  The present invention relates to an image processing apparatus.

  An image processing apparatus determines whether a document image is a color image or a monochrome image based on whether or not a color portion is present in the document image, and depending on the determination result, the image data of the document image is used for a color image. Compression is performed using a compression method or a compression method for monochrome images (see, for example, Patent Document 1).

JP 2007-28408 A

  In the image processing apparatus described above, when a color portion exists in the entire document image (that is, the entire page), the document image is determined to be a color image, and there is no color portion in the entire document image (that is, the entire page). The document image is determined to be a monochrome image. For this reason, when the document image is a monochrome image, the compression process cannot be started until the color / monochrome determination for the entire document image is completed. Therefore, the start of the compression process is delayed, and the image data of the entire original image (that is, the entire page) needs to be buffered before the compression process is started.

  The present invention has been made in view of the above problems, and an image processing apparatus that requires a small buffer capacity before compression processing when a compression method is selected according to the determination result of automatic color determination is obtained. With the goal.

  An image processing apparatus according to the present invention includes a band color determination unit that determines whether each band in a page image is a color band or a monochrome band, and a color band based on a determination result by the band color determination unit. A compression unit that executes compression processing of a color band compression method for a certain band and performs compression processing of a monochrome band compression method for the band that is a monochrome band, and compression using the color band compression method The expanded band is expanded by an expansion method corresponding to the color band compression method, and the band compressed by the monochrome band compression method is expanded by an expansion method corresponding to the monochrome band compression method. A part.

  According to the present invention, when the image processing apparatus selects a compression method according to the determination result of the automatic color determination, the buffer capacity before the compression process can be small.

FIG. 1 is a block diagram showing a configuration of an image processing apparatus according to an embodiment of the present invention. FIG. 2 is a flowchart for explaining the operation of the band color determination unit in the image processing apparatus shown in FIG. FIG. 3 is a flowchart for explaining processing after expansion in the image processing apparatus shown in FIG. FIG. 4 is a diagram illustrating an example of a page image that has a background color that is a chromatic color with a very small saturation, and that includes both color bands and monochrome bands. FIG. 5 is a diagram illustrating an example of a page image in which the end portion of the color object is positioned near the band boundary.

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

  FIG. 1 is a block diagram showing a configuration of an image processing apparatus according to an embodiment of the present invention.

  In FIG. 1, an image reading unit 1 includes an image sensor such as a CCD (Charge Coupled Device) and an AFE (Analog Front End) circuit, reads a document image from a document, and outputs image data of the document image.

  The calibration unit 2 performs calibration processing (shading correction, MTF (Modulation Transfer Function) correction, chromatic aberration correction, etc.) on the image data output from the image reading unit 1.

  The band color determination unit 3 determines whether each band in the page image is a color band or a monochrome band for the page image based on the image data after the calibration process. One band is composed of a plurality of predetermined lines.

  In this embodiment, when the number of color lines in the band is equal to or greater than a predetermined threshold value, the band color determination unit 3 determines that the band is a color band, and the number of color lines in the band. Is less than a predetermined threshold, the band is determined to be a monochrome band, and (b) at least one color in at least one of a predetermined number of lines at the beginning of the band and a predetermined number of lines at the end of the band. When there is a line, even if the number of color lines in the band is less than a predetermined threshold, it is determined that the band is a color band.

  A color line is a line in which a predetermined number or more of color pixels are included in one line, and the color pixels have a predetermined saturation condition (for example, a condition that the saturation is equal to or higher than a predetermined threshold). It is a pixel having a color. Lines that are not color lines are monochrome lines.

  The page color determination unit 4 determines whether the page image is a color image or a monochrome image. For example, the page color determination unit 4 determines that the page image is a color image when the number of color lines in the page image is greater than or equal to a predetermined value, and otherwise the page image is a monochrome image. Judge that there is. Alternatively, the page color determination unit 4 determines that the page image is a color image if there is even one color band in the page image. If there is no color band in the page image, the page image is a monochrome image. You may make it determine with there.

  The background color determination unit 5 determines the background color of the page image (that is, the background color in the page image). Specifically, the background color determination unit 5 detects the color of the leading end portion (for example, several millimeters of the leading end) of the page image as the background color.

  The main memory 6 is a volatile memory. The main memory 6 includes a band memory 21 arranged before the compression processing for each band, a page memory 22 for storing image data of the page image for compression processing, and a band arranged after the expansion processing for each band. Memory 23 is secured.

  Based on the determination result by the band color determination unit 3, the compression unit 7 executes the compression process of the color band compression method for the band that is a color band, and the monochrome band compression method for the band that is a monochrome band The compression process is executed.

  For example, the compression unit 7 executes a compression process of a 4: 2: 0 format JPEG (Joint Photographic Experts Group) method for a band that is a color band, and 4: 0 for a band that is a monochrome band. : Executes 0 format JPEG compression processing.

  The expansion unit 8 expands a band compressed by the color band compression method using a decompression method corresponding to the color band compression method, and supports a band compressed by the monochrome band compression method corresponding to the monochrome band compression method. It expands with the expansion method.

  The color image processing unit 9 performs image processing for a color image on the band that has been decompressed by the decompressing unit 8 for the page image that has been determined to be a color image by the page color determining unit 4. The monochrome image processing unit 10 executes image processing for a monochrome image on the band that has been expanded by the expansion unit 8 for the page image determined to be a monochrome image by the page color determination unit 4. The control unit 11 causes the color image processing unit 9 to process the page image determined to be a color image based on the determination result by the page color determination unit 4, and causes the monochrome image processing unit 10 to process the page image determined to be a monochrome image. Let it be processed.

  For example, image processing for color images is image processing (color conversion, screen processing, etc.) necessary for color printing, and image processing for monochrome images is image processing (screen processing, etc.) required for monochrome printing. is there.

  In this embodiment, the band color determination unit 3 determines whether the band is a color band or a monochrome band based on a predetermined saturation condition, and the color image processing unit 9 uses the saturation condition. Based on the band determined to be a monochrome band based on the background color, the background color is synthesized after the expansion by the expansion unit 8.

  Specifically, the color image processing unit 9 expands the band determined to be a monochrome band based on the saturation condition in the page image determined to be a color image by the page color determination unit 4. The background color is synthesized after the extension by the unit 8. On the other hand, for the page image determined to be a monochrome image by the page color determination unit 4, the monochrome image processing unit 10 combines the background color with the band determined to be a monochrome band based on the saturation condition. Do not do.

  In this embodiment, the color image processing unit 9 specifies the background portion in the band when the background color is combined with the band determined to be a monochrome band based on the saturation condition, and the background. The color of the part is changed to the background color, and the background color is not combined with the object (foreground) part in the band. In addition, when the JPEG compression process of the 4: 0: 0 format is executed for a band that is a monochrome band, the background color in the band is added to the background color because the saturation is zero. That's fine.

  For example, the calibration unit 2, the band color determination unit 3, the page color determination unit 4, and the background color determination unit 5 described above are realized by an ASIC (Application Specific Integrated Circuit), the compression unit 7, the expansion unit 8, The color image processing unit 9, the monochrome image processing unit 10, and the control unit 11 may be realized by executing a program with a computer.

  Next, the operation of the image processing apparatus will be described. FIG. 2 is a flowchart for explaining the operation of the band color determination unit in the image processing apparatus shown in FIG. FIG. 3 is a flowchart for explaining processing after expansion in the image processing apparatus shown in FIG.

  A document image is read from the document by the image reading unit 1, and image data of the document image (page image) after the calibration process is output from the calibration unit 2 in band units.

  The band image data is supplied to the band color determination unit 3, page color determination unit 4, and background determination unit 5, and is written into the band memory 21 by a DMA (Direct Memory Access) controller (not shown).

  Then, the band color determination unit 3 determines whether the band is a color band or a monochrome band, and notifies the compression unit 7 and the color image processing unit 9 of the determination result. The determination result for each band may be stored in the main memory 6, and the band compression unit 7 and the color image processing unit 9 may read out from the main memory 6 as necessary.

  At this time, as shown in FIG. 2, first, the band color determination unit 3 performs at least one of a predetermined number of lines at the beginning of the band (for example, 3 lines) and a predetermined number of lines at the end of the band (for example, 3 lines) Then, it is determined whether or not at least one color line exists (step S1). When there is no color line in any of the predetermined number of lines at the beginning of the band and the predetermined number of lines at the end of the band, the band color determination unit 3 has the number of color lines in the band equal to or greater than a predetermined threshold. (Step S2), and if the number of color lines in the band is not greater than or equal to a predetermined threshold, it is determined that this band is a monochrome band (step S3). In other cases, the band color determination unit 3 determines that this band is a color band (step S4).

  The compression unit 7 reads the image data of this band from the band memory 21, selects a compression method based on the determination result of the band color determination unit 3, compresses the image data of this band with the selected compression method, and performs compression The subsequent image data is stored in the page memory 22.

  In this way, the image data of the page image is compressed for each band and stored in the page memory 22.

  In parallel with this process, the page color determination unit 4 and the background color determination unit 5 operate. Then, the page color determination unit 4 notifies the control unit 11 of a determination result indicating whether the page image is a color image. The background color determination unit 5 notifies the color image processing unit 9 of the color data of the background color. The determination result by the page color determination unit 4 and the background color data by the background color determination unit 5 are stored in the main memory 6, and the control unit 11 and the color image processing unit 9 read out from the main memory 6 as necessary. It may be.

  After that, the decompression unit 8 sequentially reads the compressed band image data, decompresses the decompressed image data in a decompression method corresponding to the compression method of the read compressed image data, and decompresses the compressed image data. The image data obtained in this way is stored in the band memory 23 (step S21).

  At this time, the control unit 11 determines whether or not the page image is a color image based on the determination result by the page color determination unit 4 (step S22), and the page image is not a color image (that is, a monochrome image). If there is, the control unit 11 causes the monochrome image processing unit 10 to process the image data obtained by decompression (step S23).

  On the other hand, when the page image is a color image, the control unit 11 causes the color image processing unit 9 to process the image data obtained by the expansion (steps S24 to S26).

  First, the color image processing unit 9 determines whether or not this band is a monochrome band based on the determination result by the band color determination unit 3 (step S24).

  If this band is a monochrome band, the color image processing unit 9 combines the background color with this band (step S25), and executes image processing on the combined band (step S26). On the other hand, if this band is not a monochrome band (that is, a color band), the color image processing unit 9 performs image processing on this band without synthesizing the background color (step S26).

  If this band is not the last band of the page image, the processing from step S21 is executed on the next band. If this band is the last band of the page image, the processing ends (step S27). ).

  As described above, according to the above embodiment, the band color determination unit 3 determines whether each band in the page image is a color band or a monochrome band, and the compression unit 7 includes the band color determination unit. Based on the determination result of No. 3, the compression process of the color band compression method is executed for the band that is a color band, and the compression process of the compression method for the monochrome band is executed for the band that is a monochrome band. The expansion unit 8 expands a band compressed by the color band compression method using a decompression method corresponding to the color band compression method, and supports a band compressed by the monochrome band compression method corresponding to the monochrome band compression method. It expands with the expansion method.

  As a result, when the compression method is selected according to the determination result of the automatic color determination, the buffer capacity before the compression process can be reduced. For example, when the image processing apparatus is a color image forming apparatus such as a color printer or a color multifunction peripheral, for example, the main memory 6 is caused by a shortage of the main memory 6 even if the capacity of the main memory 6 is small. This makes it difficult to cause a problem that the scanning operation of the document image is interrupted until the free space is secured.

  In addition, since the compression process can be started for each band without waiting for the determination whether the page image is a color image or a monochrome image, the waiting time due to the automatic color determination can be shortened.

  FIG. 4 is a diagram illustrating an example of a page image that has a background color that is a chromatic color with a very small saturation, and that includes both color bands and monochrome bands. In the case of the page image as shown in FIG. 4, since the saturation of the background color is very small, it is determined that the band having no color object is a monochrome band. However, as described above, the background color is synthesized after being expanded with respect to the monochrome bands 101 to 103, so even if the background color information is lost during compression, a uniform background color background is restored over the entire area of the page image. Is done.

  FIG. 5 is a diagram illustrating an example of a page image in which the end portion of the color object is positioned near the band boundary. As shown in FIG. 5, when the end of the color object 111 is in a small band 112, the band 112 is not determined as a monochrome band, and all the bands including the color object 111 are determined as color bands. .

  The above-described embodiments are preferred examples of the present invention, but the present invention is not limited to these, and various modifications and changes can be made without departing from the scope of the present invention. is there.

  For example, in the above-described embodiment, the color image processing unit 9 combines the background color with the monochrome band only when the background color is chromatic, and when the background color is an achromatic color, The background color may not be synthesized.

  The present invention is applicable to a color image forming apparatus such as a color printer or a color multifunction peripheral.

3 Band color determination unit 4 Page color determination unit 5 Background color determination unit 7 Compression unit 8 Expansion unit 9 Color image processing unit (an example of an image processing unit)

Claims (5)

A band color determination unit for determining whether each band in the page image is a color band or a monochrome band;
Based on the determination result by the band color determination unit, the compression process of the color band compression method is performed on the band that is a color band, and the compression process of the monochrome band compression method is performed on the band that is a monochrome band A compression unit for executing
The band compressed by the color band compression method is expanded by an expansion method corresponding to the color band compression method, and the band compressed by the monochrome band compression method is changed to the monochrome band compression method. An expansion section that expands with a corresponding expansion method;
An image processing apparatus comprising: A background color determination unit for determining the background color of the page image;
An image processing unit that performs image processing on a band that has been expanded by the expansion unit;
The band color determination unit determines whether the band is a color band or a monochrome band based on a predetermined saturation condition,
The image processing unit, for the band determined to be a monochrome band based on the saturation condition, synthesizing the background color after expansion by the expansion unit;
The image processing apparatus according to claim 1. A page color determination unit for determining whether the page image is a color image or a monochrome image;
In the page image determined to be a color image by the page color determination unit, the image processing unit performs the expansion unit on the band determined to be a monochrome band based on the saturation condition. In the page image determined to be a monochrome image by the page color determination unit after combining the background color after expansion, for the band determined to be a monochrome band based on the saturation condition, Do not combine the background color,
The image processing apparatus according to claim 2.   The image processing unit, when combining the background color after expansion by the expansion unit to the band determined to be a monochrome band based on the saturation condition, the color of the background portion in the band The image processing apparatus according to claim 2, wherein the image processing apparatus is changed to a background color.   The band color determination unit (a) determines that the band is a color band when the number of color lines in the band is equal to or greater than a predetermined threshold, and the number of color lines in the band is a predetermined threshold. The band is determined to be a monochrome band, and (b) at least one color line is present in at least one of the predetermined number of lines at the beginning of the band and the predetermined number of lines at the end of the band. 5. If present, the band is determined to be a color band even if the number of color lines in the band is less than a predetermined threshold value. The image processing apparatus according to item.

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