JP2010021628A - Image processor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the following problem: an image processor having a color scan function also has a black character processing function of converting black characters/thin lines to pure black signals and an ACS (Auto Color Select) function of determining whether a read original is color or monochrome and switching a color mode of scan, however a single determination threshold is not enough for a variation in a reader. <P>SOLUTION: In each of the time of pressure plate read and the time of ADF (Auto Document Feeder) read, the sensitivity of black character processing and the sensitivity of ACS determination are set independently of each other. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention reads a document, performs chromatic / achromatic color determination of pixels in the document, and based on this, converts a pixel signal corresponding to a black character / thin line in the document to a pure black signal, The present invention relates to an image processing apparatus that performs color / monochrome determination.

In a conventional image processing apparatus having a color scan function, a black character is determined when a black character / thin line (hereinafter referred to as a black character) is color-scanned to determine a black character portion and convert the black character portion into a pure black signal. There is a processing function.

  Also, chromatic / achromatic colors are determined for each pixel of the scanned image obtained by digitally reading the document, and the color / monochrome determination of the document is performed based on the ratio of the pixels in the document (the entire document). There is an ACS function for switching the scanning color mode. ACS is an abbreviation for Auto Color Select.

  The former increases the sharpness of the black character portion during color scanning, and provides a high-quality color scan image.

  The latter provides a scan image in an optimal color mode without requiring the user to perform complicated color mode settings.

  These functions realize black character portion determination and chromatic / achromatic color determination by image processing for color scanned image data.

  However, although these determinations are made based on specific threshold values, the results may not always match the results desired by the user. This is caused by variations in device characteristics such as optical characteristics and mechanical blur of a scanner that reads a document, and the threshold value itself deviates from the user's sense.

  In order to eliminate such a difference between the result desired by the user and the image processing result, a proposal as in Patent Document 1 has been made.

In this proposal, a desired attribute result is input from an operation unit to an image processing apparatus that determines image attributes such as a character area, a photograph area, and a halftone dot area on a document. Then, the determination parameter is gradually changed until the result of the attribute determination by reading the document becomes the desired attribute result, and this is repeated. Thus, an image on which an image processing result desired by the user is applied is provided.
JP 10-271327 A

  However, in the conventional technique, it is necessary to repeat the determination process until the result desired by the user is obtained. If there is a large difference between the determination result based on the initial parameters and the desired determination result, a long processing time is required. Further, when the result provided by the image processing apparatus is not sufficient, there is a problem that there is no means for correction and it is difficult to obtain the result desired by the user.

In order to solve the above-described problem, the image processing apparatus of the present invention includes a first achromatic / chromatic determining unit and a second chromatic determining unit that determine whether the operation unit and the target pixel are chromatic or achromatic. For a pixel determined to be a character part / line drawing part by the image area separating means and the image area separating means for separating the character / line drawing part and the non-character part / non-line drawing part on the original / achromatic determination means A black character processing unit that performs black character processing based on a determination result of the first chromatic / achromatic determination unit and a color document or a monochrome document based on the determination result of the second chromatic / achromatic determination unit Color determining means for determining whether or not the first threshold value of the first chromatic / achromatic determining means and the second threshold value of the second chromatic / achromatic determining means are determined from the operation unit. It has a setting means to set according to each input.

  An image processing apparatus can be realized in which the sensitivity of the ACS function and the sensitivity of the black character processing function can be set optimally when reading the ADF and when reading the pressure plate. By realizing these, it is possible to provide the image processing result desired by the user.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

  As shown in FIG. 1, the proposed image processing apparatus includes a scanner 102, an image processing unit 101, and an operation unit 111.

  A scanner 102 that acquires digital image data by optically reading an image on a document outputs three channel signals R1, G1, and B1 (red, green, and blue) for each pixel as digital image data. FIG. 4 illustrates the scanner 102 in more detail. This is composed of a pressure plate glass 401, a reading unit 402, and an ADF (Auto Document Feeder).

  When the original 404 is placed on the pressure plate glass 401, the reading unit performs pressure plate reading in which an image on the original is scanned and read while moving from the position B to the position C.

  When the original 404 is placed on the ADF, the original 404 is conveyed inside the ADF. The reading unit 402 moves to the position A to fix the position, and performs ADF reading in which an image on the original is scanned and read.

  The image area separation unit 103 scans the digital image data in a raster shape, determines whether the pixel of interest is an edge portion, and checks whether the pixel is a pixel constituting a halftone image on the document. A pixel that is an edge and is not a halftone dot pixel is determined as an edge portion of the line drawing. By doing so, it is possible to separate an edge portion that may be a character (character portion) / line drawing (line drawing portion) and a portion that is a non-character (non-character portion) / non-line drawing (non-line drawing portion) on the document. The output of the image area separation unit 103 is an image area signal indicating a pixel determined to be an edge portion of a character / line drawing.

  The first color conversion unit 104 performs a function operation on the R1, G1, and B1 signals from the scanner 102, and converts them into a lightness signal L1 representing brightness and chromaticity signals (Ca1, Cb1). The lightness signal L1 and the chromaticity signals (Ca1, Cb1) are measured in terms of CIE 1976 (L *, a *, b *) color space three variables L *, a *, b * and CIE 1976 (L *, u *). , V *) The color space may be three variables L *, u *, v *, or any color space determined in a simplified manner.

The following equation (1) shows an example of a conversion equation for simply color-converting the R1, G1, and B1 signals to the lightness and chromaticity signals L1, Ca1, and Cb1. This is used in the example.
L1 = (R1 + 2 * G1 + B1) / 4
Ca1 = (R1-G1) / 2
Cb1 = (R1 + G1-2 * B1) / 4 (1)

  These L1, Ca1, and Cb1 signals are input to the black character processing unit 107, the first chromatic / achromatic determination unit 105, and the second chromatic / achromatic determination unit 106. In the present specification, the chromatic / achromatic determination unit may be referred to as an achromatic / chromatic determination unit.

  The absolute value of the vector formed by the chromaticity signals Ca1 and Cb1 of the target pixel represents the saturation, and the direction represents the hue.

  The first chromatic / achromatic determination unit 105 compares the absolute value of the vector formed by Ca1 and Cb1 with the first threshold value and evaluates it to determine whether the pixel of interest is a chromatic color or an achromatic color. Output chromatic / achromatic signal. In addition, the first threshold value may be provided for each quadrant depending on where in the first quadrant to the fourth quadrant of the Ca1 and Cb1 planes, that is, the hue.

  The second chromatic / achromatic determination unit 105 compares the absolute value of the vector formed by Ca1 and Cb1 with the second threshold value and evaluates to determine whether the pixel of interest is a chromatic color or an achromatic color. Output chromatic / achromatic signal. Further, a second threshold value may be provided for each quadrant depending on where in the first quadrant to the fourth quadrant of the Ca1 and Cb1 planes, that is, the hue.

  The black character processing unit 107 includes an image area signal that is an output of the image area separation unit 103, a first chromatic / achromatic determination signal that is an output of the first chromatic / achromatic determination unit 105, and a first color. Based on the L1, Ca1, and Cb1 signals from the conversion unit 104, black character processing is performed on the target pixel. If the pixel of interest is an edge portion of a character / line drawing and has an achromatic color, it is determined that the pixel of interest is a black character / line drawing. Then, the Ca1 and Cb1 signals of the target pixel are suppressed to zero. As a result, the saturation of the pixel of interest becomes 0, and it can be seen from Equation (2) described later that the RGB value represents an achromatic color of R = G = B. If the target pixel is a non-character / non-line image or a chromatic color, no processing is applied to the Ca and Cb signals. Such processing is performed, and L2, Ca2, and Cb2 are output.

The second color conversion unit 108 performs color conversion of L2, Ca2, and Cb2 into R2, G2, and B2 signals. The following equation (2) shows an example of a conversion equation calculated by the second color conversion unit, and is obtained from the above-described equation (1).
R2 = (4 * L2 + 5 * Ca2 + 2 * Cb2) / 4
G2 = (4 * L2-3 * Ca2 + 2 * Cb2) / 4
B2 = (4 * L2 + Ca2-6 * Cb2) / 4 Formula (2)

  The ACS determination unit 110 counts the amount of the second chromatic / achromatic determination signal present in the read digital image data and compares it with a threshold value, so that the read original is a color original or a monochrome original. Determine if there is.

  If there is a chromatic color determination result equal to or greater than the threshold value, the document is determined to be a color document, and if the threshold value is not satisfied, the document is determined to be a monochrome document. Then, an ACS determination signal is output.

The color / monochrome conversion unit 109 receives the ACS determination signal from the ACS determination unit 110 and the R2, G2, and B2 signals from the second color conversion unit 108, and colors the R2, G2, and B2 signals based on the ACS determination signal. The R3, G3, and B3 signals are output after conversion. When the ACS determination signal indicates a color original, an output signal is generated by the following equation (3).
R3 = R2
G3 = G2
B3 = B2... Formula (3)

  When the ACS determination signal indicates a monochrome document, the color image signal is converted into a monochrome image signal.

The following equation (4) is an example of a conversion equation for performing color / monochrome conversion.
R3 = G3 = B3 = (3 * R2 + 4 * G2 + B2) / 8 (8)
The monochrome image signal is a one-channel signal, but the monochrome image signal may be placed on the three signal lines R3, G3, and B3 as shown in Equation (4), or the monochrome image signal may be placed on any one of the channels. Also good.

  The operation unit 111 includes at least a display unit 201, a start key 204, and a stop key 203 as shown in FIG.

  The display unit 201 is a display device such as an LCD (Liquid Crystal Display), and may further have a touch panel function.

A start key 202 is a hard key for designating operation start of the image processing apparatus 101.
A stop key 203 is a hard key for designating operation stop of the image processing apparatus 101.

  In this embodiment, the operation unit 111 is connected to the first chromatic / achromatic determination unit 105, the second chromatic / achromatic determination unit 106, and the ACS determination unit.

  FIG. 3 is a flowchart showing an embodiment of the present proposal. The operation of the proposed image processing apparatus will be described with reference to FIG. 3 and other drawings.

  The operation unit 111 is capable of setting input for ACS determination and setting input for black character processing at the time of reading the pressure plate and at the time of reading the ADF. FIG. 5 shows an ACS determination setting screen when reading the pressure plate. FIG. 6 shows a setting screen for ACS determination at the time of ADF reading. FIG. 7 shows a setting screen for black character processing when the pressure plate is read. FIG. 8 shows a setting screen for black character processing during ADF reading. These four may be displayed on independent screens or may be displayed together on one screen.

  When scanning the ADF, color deviation and blurring occur on the digital image data due to the impact of the flapping of the document that occurs when transporting the paper, the entry of the document into components such as the transport roller (not shown), and the escape shock. Resulting in.

  Therefore, it is desirable to set optimum threshold values used for various determinations for ADF reading and pressure plate reading.

  In the ACS setting screens of FIGS. 5 and 6, color determination priority is given to the left of the pointer 501 and pointer 601 and monochrome judgment is given to the right. FIG. 5 and FIG. 6 show examples in which ± 3 steps can be set with respect to the center value.

  The position of the pointer may be instructed directly by a touch panel method, or a direction key may be separately provided on the operation unit 111 with a hard key, and an instruction may be received from this.

  In the black character processing setting screens of FIGS. 7 and 8, the color character determination priority is given to the left of the pointer 701 and pointer 801, and the black character judgment is given to the right. FIG. 7 and FIG. 6 show examples in which ± 3 steps can be set with respect to the center value.

  The position of the pointer may be instructed directly by a touch panel method, or a direction key may be separately provided on the operation unit 111 with a hard key, and an instruction may be received from this.

  Here, the color determination priority on the ACS setting screen is obtained by setting the second threshold value of the second chromatic / achromatic determination unit 106 described above to a value that facilitates color determination. That is, the threshold value becomes smaller when viewed on the Ca and Cb planes. On the other hand, the monochrome determination priority is that the threshold value is increased.

  Seven levels of these threshold values including the central value are prepared and associated with the positions indicated by the pointer 501 and the pointer 601.

  Further, the color determination priority of the ACS setting screen is a value that makes the threshold value of the ACS determination unit 110 easy to perform color determination. That is, the threshold value becomes smaller. On the other hand, the monochrome determination priority is that the threshold value is increased.

  Seven levels of these threshold values including the central value may be prepared and associated with the positions indicated by the pointer 501 and the pointer 601 together with the threshold value of the second achromatic color determination unit 106.

  Further, the color character determination priority on the black character processing setting screen is obtained by setting the first threshold value of the first chromatic / achromatic determination unit 105 to a value that facilitates color determination. That is, the threshold value becomes smaller when viewed on the Ca and Cb planes. On the other hand, the black character determination priority is that the threshold value is increased.

  Seven levels of these threshold values including the central value are prepared, and are associated with the positions indicated by the pointer 701 and the pointer 801.

  In step 302, input from the user on the various setting screens shown in FIGS. 5 to 8 is accepted.

  In step 302, it is determined whether the document is loaded on the pressure plate glass 401 of the scanner 102 or the ADF.

If a document is loaded on the ADF 403 in step 302, a threshold corresponding to the setting value received on the ACS setting screen at the time of ADF reading shown in FIG. At the same time, the ACS determination unit 110 is set. (Step 303)
Further, a threshold value corresponding to the set value received on the black character processing setting screen at the time of ADF reading shown in FIG. 8 is set in the first chromatic / achromatic determination unit 105. (Step 304)
When the operation unit 111 receives an input for starting an image processing operation, the scanner 102 starts reading a document. (Step 305)
The image processing unit 101 shown in FIG. 1 performs image processing using the threshold values set in steps 303 and 304. (Step 306)
When an original is stacked on the pressure plate glass 401 in step 302, a threshold corresponding to the setting value received on the ACS setting screen at the time of reading the pressure plate shown in FIG. 5 is set in the second chromatic / achromatic determination unit 106. To do. At the same time, the ACS determination unit 110 is set. (Step 307)
Further, a threshold corresponding to the setting value received on the black character processing setting screen at the time of reading the pressure plate shown in FIG. 7 is set in the first chromatic / achromatic determination unit 105. (Step 308)
When the operation unit 111 receives an input for starting an image processing operation, the scanner 102 starts reading a document. (Step 309)
The image processing unit 101 shown in FIG. 1 performs image processing using the threshold values set in steps 307 and 308. (Step 310)
According to the embodiment of the present invention described above, it is possible to realize an image processing apparatus capable of setting the optimum sensitivity of the ACS function and the sensitivity of the black character processing function at the time of ADF reading and pressure plate reading. By realizing these, it is possible to provide the image processing result desired by the user.

Image processing device Configuration diagram of the operation unit flowchart Scanner configuration diagram ACS setting screen when reading pressure plate ACS setting screen when reading ADF Black character processing setting screen when reading pressure plate Black character processing setting screen when reading ADF

Claims (3)

A first image for converting an image on a document optically read by a reading device into digital image data and determining whether the operation unit and the target pixel are chromatic or achromatic in the image processing device that performs image processing Achromatic / chromatic determining means, second chromatic / achromatic determining means, image area separating means for separating a character / line drawing part and a non-character / non-line drawing part on a document, and characters by the image area separating means A black character processing unit that performs black character processing on a pixel determined to be a part / line drawing unit based on a determination result of the first chromatic / achromatic determination unit, and a second chromatic / achromatic determination unit Color determination means for determining whether the document is a color document or a monochrome document based on the determination result, and the first threshold value of the first chromatic / achromatic determination means and the second chromatic / no color According to the input from the operation unit An image processing apparatus comprising setting means for setting each. The color determination means counts the amount of pixels determined to be chromatic or achromatic by the second chromatic / achromatic determination means over the entire document, and results of comparison between the count value and a third threshold value The color of the document based on the
The third threshold value of the color determination unit is also set based on the set value when the threshold value of the second chromatic / achromatic determination unit is set according to the input from the operation unit. An image processing apparatus according to 1.   The reading apparatus includes a pressure plate reading method and an ADF reading method. When setting from the operation unit, the first threshold value of the first chromatic / achromatic determining means at the time of reading the pressure plate and the first value at the time of ADF reading. The image processing apparatus according to claim 1, wherein the second threshold value of the second chromatic / achromatic determination can be set independently.

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