JP5005734B2 - Image processing apparatus, image processing method, and image processing program - Google Patents

Description

  The present invention relates to, for example, an image processing apparatus such as a copier or a printer that identifies the type of an input image and performs image processing according to the identified image type, an image processing method, and an image processing program.

  2. Description of the Related Art Conventionally, some digital multi-function peripherals functioning as copiers or printers have a function of performing image processing according to the type of input image. For example, in order to improve copy image quality, the digital multi-function peripheral identifies whether the image read by the scanner is a character image, a line drawing, or a photographic image (image area identification), and performs filter processing and gradation processing according to the identification result. Alternatively, the image processing content such as inking processing is switched. For example, image processing for emphasizing characters is performed on a character image (character region), and image processing for smoothing is performed on a photographic image (photo region). In addition, for a character image (character region), an inking process may be performed in which black (a single black color) is printed on a black character portion.

  However, in the conventional image area identification process, a perfect identification result is not always obtained in practice. For example, in the image area identification processing, not only achromatic characters but also chromatic characters, and characters on a color background are identified. These characters are difficult to detect from single color signal values (signal components of each color). For this reason, conventional image area identification processing is often performed for each component (channel) in accordance with each color component (each color channel) of the input system or output system.

  In such an image area identification process for dealing with a chromatic character or a character on a color background, it is necessary to extract a feature amount for identifying an image in all channels of the input system or the output system. In particular, in order to distinguish a rough halftone dot and a character with high accuracy, it is necessary to perform identification processing using a partial image (operator) having a large size (image region) for one pixel of one channel. When such identification processing is executed for a plurality of channels, the load on the identification processing increases, and the load on the entire image processing increases.

  In order to solve such a problem, Japanese Patent Laid-Open No. 2001-245142 proposes a method of using only the G signal channel of the input signals. Japanese Laid-Open Patent Publication No. 2007-243330 proposes a method that uses the difference between luminance and color difference. However, the technique described in Japanese Patent Application Laid-Open No. 2001-245142 has a problem that, for example, red or yellow color characters on a white background with little variation in the G signal cannot be detected. In addition, the technique described in Japanese Patent Application Laid-Open No. 2007-243330 has a problem that, for example, it is difficult to detect a yellow character on a white background in which only the B signal is changed.

  An object of one aspect of the present invention is to provide an image processing apparatus, an image processing method, and an image processing program capable of efficiently and accurately identifying the type of an image, and capable of reliably performing appropriate image processing. .

An image processing apparatus according to an aspect of the present invention includes an input unit that inputs image data including pixels composed of a plurality of component values , and each component value of each pixel in the image data input by the input unit. a mixing ratio calculation means for calculating a mixing ratio of the components, the sum of a value obtained by multiplying the calculated mixture ratio by each pixel value of the components the mixing ratio calculating means in the input image data by said input means A calculation means for calculating the luminance equivalent value of each pixel; a character determination means for determining whether each pixel is a pixel belonging to a character image or a line drawing based on the luminance equivalent value calculated by the calculation means; and the character Image processing means for performing different image processing on pixels belonging to a character image or line drawing and pixels not belonging to the character image or line drawing according to the determination result by the determination means. That.

An image processing apparatus according to an aspect of the present invention includes an input unit that inputs image data including pixels composed of a plurality of component values , and each component value of each pixel in the image data input by the input unit. A mixture ratio calculating means for calculating a mixture ratio of components; a color determining means for determining whether each pixel in the image data input by the input means is chromatic or achromatic; and image data input by the input means Calculating means for calculating the sum of values obtained by multiplying the value of each component by the mixing ratio calculated by the mixing ratio calculating means for each pixel in the pixel as a luminance equivalent value of each pixel, and the luminance equivalent calculated by the calculating means Character determination means for determining whether each pixel is a pixel belonging to a character image or line drawing based on the value, a determination result by the character determination means, and the color Different image processing for pixels belonging to a chromatic character image or line drawing, pixels belonging to an achromatic character image or line drawing, and pixels not belonging to the character image or line drawing, depending on the determination result by the determination means Image processing means.

According to an image processing method as an aspect of the present invention, image data including pixels composed of a plurality of component values is input, and a mixing ratio of each component is calculated from each component value for each pixel in the input image data. Then, for each pixel in the input image data, a sum of values obtained by multiplying the value of each component and the calculated mixing ratio is calculated as a luminance equivalent value of each pixel, and based on the calculated luminance equivalent value It is determined whether each pixel is a pixel belonging to a character image or a line drawing, and different image processing is performed on pixels belonging to the character image or line drawing and pixels not belonging to the character image or line drawing according to the determination result. Do.

An image processing method as one aspect of the present invention inputs image data composed of pixels composed of a plurality of component values, and determines whether each pixel in the input image data is a chromatic color or an achromatic color. and calculates the mixing ratio of the components from the value of each component for each pixel in the image data the input, multiplied by the mixing ratio which is the calculated value of each component for each pixel in the image data the input The sum of the values is calculated as the luminance equivalent value of each pixel, and based on the calculated luminance equivalent value, it is determined whether or not each pixel is a pixel belonging to a character image or a line drawing. Depending on the achromatic color determination result, pixels belonging to a chromatic character image or line drawing, pixels belonging to an achromatic character image or line drawing, and pixels not belonging to the character image or line drawing are compared. Te, perform different image processing.

An image processing program according to an aspect of the present invention has a function of inputting image data composed of pixels composed of values of a plurality of components to a computer, and each component from the value of each component for each pixel in the input image data. a function of calculating a mixing ratio of the function of calculating the sum of values obtained by multiplying the mixing ratio which is the calculated value of each component for each pixel in the image data the input as the luminance equivalent value of each pixel, A function for determining whether each pixel is a pixel belonging to a character image or a line drawing based on the calculated luminance equivalent value, and a pixel belonging to the character image or line drawing and a pixel belonging to the character image or line drawing according to the determination result And a function of performing different image processing on each pixel that is not present.

An image processing program according to an aspect of the present invention includes a function of inputting image data including pixels composed of a plurality of component values to a computer, and whether each pixel in the input image data is chromatic or achromatic. a function of determining whether there are, the function of calculating the mixture ratio of the components for each pixel in the image data the input from the value of each component, the calculated value of each component for each pixel in the image data the input A function of calculating a sum of values obtained by multiplying the mixed ratio as a luminance equivalent value of each pixel, and whether each pixel is a pixel belonging to a character image or a line drawing based on the calculated luminance equivalent value. Depending on the determination function and the determination result and the determination result of the chromatic color or the achromatic color, there may be a pixel belonging to a chromatic character image or line image, and an achromatic character image. And pixels belonging to a line drawing, with respect to a pixel not belonging to the character image or line drawing, thereby realizing the function of performing different image processing.

  According to an aspect of the present invention, it is possible to provide an image processing apparatus, an image processing method, and an image processing program that can identify the type of image efficiently and with high accuracy and can reliably perform appropriate image processing.

FIG. 1 is a schematic diagram schematically illustrating an example of the overall configuration of a digital multifunction peripheral. FIG. 2 is a block diagram illustrating the configuration of the digital multifunction peripheral and the main control unit. FIG. 3 is a block diagram illustrating a configuration example of the image processing unit as the first embodiment. FIG. 4A is a diagram for explaining a method for calculating a difference between pixels in the vertical direction. FIG. 4B is a diagram for explaining a method for calculating a difference between pixels in the horizontal direction. FIG. 5A and FIG. 5B are diagrams for explaining a method for calculating a difference between pixels in an oblique direction. FIG. 6 is a block diagram illustrating a configuration example of an image processing unit according to the second embodiment. FIG. 7 is a block diagram illustrating a configuration example of an image processing unit as a third embodiment. FIG. 8 is a flowchart for explaining the flow of image processing according to the fourth embodiment. FIG. 9 is a flowchart for explaining the flow of image processing according to the fifth embodiment.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a schematic diagram schematically showing an example of the overall configuration of the digital multifunction machine 1.
A digital multifunction peripheral 1 shown in FIG. 1 functions as an image processing apparatus or an image forming apparatus. A digital multifunction device 1 shown in FIG. 1 has a function as a copier, a scanner, a printer, a facsimile, or a network communication device. In the configuration example illustrated in FIG. 1, the digital multifunction peripheral 1 includes a main control unit 10, a scanner 11, a printer 12, a facsimile communication unit (FAX unit) 13, a network communication unit (NW unit) 14, and an operation unit 15. .

  The main control unit 10 controls the entire digital multi-function peripheral 1. That is, the main control unit 10 receives an operation instruction from the user through the operation unit (control panel) 15 and controls the scanner 11, printer 12, facsimile communication unit 13, network communication unit 14, and operation unit 15. The main control unit 10 includes an image processing unit that processes image data.

  The scanner 11 reads an image on a recording medium (original). The scanner 11 has a reading unit (not shown) that optically scans an image of a document and converts it into image data. The reading unit supplies the read image data to the main control unit 10. For example, the reading unit includes a driving mechanism, a CCD line sensor, and a signal processing unit (all not shown). The reading unit reads an image of the document by the CCD line sensor while moving in the sub-scanning direction with respect to the document by the driving mechanism. The CCD line sensor is composed of a plurality of CCD sensors arranged in the main scanning direction with respect to the document. The CCD line sensor converts reflected light from the document into an analog image signal. The signal processing unit converts an analog image signal read by the CCD line sensor into a digital image signal.

  In this embodiment, the scanner 11 converts a document image into a color image composed of signal values (primary color system pixel values) of red (R), green (G), and blue (B) color components. It shall be read as data. In the present embodiment, each pixel (color of each pixel) of the image data read by the scanner 11 has a density value (hereinafter simply referred to as R) as a signal value of R component, and a signal of G component. It is expressed by a density value as a value (hereinafter simply referred to as G) and a density value as a B component signal value (hereinafter simply referred to as B).

  The printer 12 forms an image for printing on an image forming medium. For example, when performing copy processing, the main control unit 10 converts an image of a document read by the scanner 11 into image data for printing. The printer 12 prints image data of a document processed for printing by the main control unit 10 on a copy sheet. As the printer 12, a printer of any image forming method can be applied. For example, the printer 12 may be a laser printer or an inkjet printer. In the printer 12, image data composed of the signal values of the cyan (C), magenta (M), and yellow (Y) color components (complementary color pixel values) and the black (K) component are printed. Let it be image data.

  The facsimile communication unit (FAX unit) 13 is an interface for transmitting and receiving image data as facsimile data. The FAX unit 13 is connected to a telephone line. The FAX unit 13 transmits and receives image data via a telephone line by a facsimile transmission method. The network communication unit (NW unit) 14 is an interface for performing network communication such as a LAN. For example, when the digital multi-function peripheral 1 is used as a network scanner, the NW unit 14 sends image data processed by the main control unit 10 to a destination device on the network designated by the operation unit 15 (for example, To the user terminal.

  The operation unit (control panel) 15 is used by the user to input an operation instruction or display guidance for the user. The operation unit 15 includes a display device and operation keys. For example, the operation unit 15 includes a liquid crystal display device with a built-in touch panel and hard keys such as a numeric keypad.

Next, the configuration of the main control unit 10 will be described.
FIG. 2 is a block diagram illustrating a configuration example of the digital multifunction peripheral 1 and the main control unit 10.
As shown in FIG. 2, the main control unit 10 includes a CPU 21, a main memory 22, an HDD 23, an input image processing unit 24, a page memory 25, an output image processing unit 26, and the like.
The CPU 21 controls the entire digital multi-function peripheral 1. The CPU 21 implements various functions, for example, by executing a program stored in a program memory (not shown). The main memory 22 is a memory for storing work data and the like. The CPU 21 implements various processes by executing various programs using the main memory 22.

  For example, the CPU 21 realizes copy control by controlling the scanner 11 and the printer 12 in accordance with a copy control program. That is, the digital multi-function peripheral 1 functions as a copier when the CPU 21 executes a copy control program.

  Further, the CPU 21 realizes a facsimile function by controlling the scanner 11 and the facsimile communication unit 13 in accordance with a facsimile control program. Further, the CPU 21 realizes a network scan process by controlling the scanner 11 and the network communication unit 14 in accordance with a network scan control program.

  The HDD (hard disk drive) 23 is a nonvolatile large-capacity memory. For example, the HDD 23 stores image data. The HDD 23 stores setting values (default setting values) for various processes. Further, the HDD 23 may store a program executed by the CPU 21.

  The input image processing unit 24 processes an input image. The input image processing unit 24 processes input image data input from the scanner 11 or the like according to the operation mode of the digital multi-function peripheral. The CPU 21 instructs the input image processing unit 24 on the processing content corresponding to the operation mode. In the configuration example illustrated in FIG. 2, the input image processing unit 24 functions as a scanner-type image processing unit that processes an image read by the scanner 11 as an input image. In this case, the input image processing unit 24 performs shading correction processing, interline correction processing, filter processing, gradation conversion processing, compression processing, and the like on the image data read by the scanner 11.

  The shading correction process is a process for correcting the image data in accordance with the sensitivity variation of each photoelectric conversion element in the CCD or the light distribution characteristic of a lamp (not shown) for illuminating the document. The inter-line correction process is a process for correcting a physical positional shift of each of the RGB sensors in the CCD line sensor of the scanner 11. In the gradation conversion process, for example, the value of each pixel constituting the image data is converted according to a lookup table (not shown). The compression process is a process for compressing image data. The page memory 25 stores code data as compressed image data.

  The various image processes in the input image processing unit 24 may be realized by the CPU 21 executing a program for image processing. Further, the image processed by the input image processing unit 24 is not limited to the image data input from the scanner 11. For example, the input image processing unit 24 may process image data received by the NW unit 14 via a network or image data received by facsimile communication by the FAX unit 13 as an input image.

  The page memory 25 is a memory for storing image data to be processed. For example, the page memory 25 stores color image data for one page. The page memory 25 is controlled by a page memory control unit (not shown). In the configuration example shown in FIG. 2, the page memory 25 stores image data as a processing result processed by the input image processing unit 24.

  The output image processing unit 26 processes the output image. In the configuration example illustrated in FIG. 2, the output image processing unit 26 functions as a printer-type image processing unit that generates image data to be printed on paper by the printer 12. For example, the output image processing unit 26 converts the image data stored in the page memory 25 into image data for a printer. The various image processes as the output image processing unit 26 may be realized by the CPU 21 executing an image processing program.

Next, image processing in the input image processing unit 24 will be described.
As described above, the input image processing unit 24 performs various image processing on the image data input from the input system such as the scanner 11. For example, the input image processing unit 24 performs shading correction processing, interline correction processing, color conversion processing, scaling processing, filter processing, inking processing, gamma correction, gradation on image data input by the scanner 11. Various image processing such as processing and compression processing are performed.

  The shading correction process is a process for correcting the image data in accordance with the sensitivity variation of each photoelectric conversion element in the CCD or the light distribution characteristic of a lamp (not shown) for illuminating the document. The inter-line correction process is a process for correcting a physical positional shift of each of the RGB sensors in the CCD line sensor of the scanner 11.

  The color conversion process performs a pixel conversion process on input image data. For example, the scanner 11 often reads an image of a document as color image data composed of R (red), G (green), and B (blue) signals, and the printer 12 reads C (cyan), M (magenta), and Y Many print color image data composed of (yellow) and K (black) signals. In such a case, the pixel conversion process converts the color image composed of R, G, B signals input from the scanner 11 into image data for printing composed of C, M, Y, K signals.

The filter process is a process for correcting image data in accordance with the type of image. The filter process is, for example, an MTF correction process. The inking process is a process for detecting a pixel area such as a black character to be printed with a single black color in the image data. The inking process is a process for improving the reproducibility of a black monochrome part such as a black character. The gamma correction process is a process for correcting image data in accordance with the gamma characteristic of the printer 12. In the gradation processing, image data is screen-processed. In the gradation processing, for example, the value of each pixel constituting the image data is converted according to a lookup table (not shown). The compression process is a process for compressing image data.
The various image processes as described above are executed as an image process for converting the image data stored in the page memory 25 by the output image processing unit 26 into image data optimized as a print image. Anyway.

Hereinafter, first to fifth embodiments as image processing units applied as the input image processing unit 24 will be described.
First, the first embodiment will be described.
FIG. 3 is a block diagram illustrating a configuration example of the image processing unit 100 according to the first embodiment.
In the configuration example illustrated in FIG. 3, the image processing unit 100 includes an input interface (I / F) 101, a color conversion unit 102, a mixture ratio calculation unit 103, a calculation unit 104, a feature amount calculation unit 105, a character determination unit 106, a variable determination unit 106. A double processing unit 107, a filter processing unit 108, a gradation processing unit 109, and an output interface (I / F) 110 are configured.

  The input I / F 101 is an interface for acquiring image data from an input system such as the scanner 11 or various external interfaces. Here, it is assumed that the input I / F 101 acquires color image data composed of red (red, R), green (green, G), and blue (blue, B) signals read by the scanner 11. To do. The input I / F 101 supplies the input color image data to the color conversion unit 102, the mixture ratio calculation unit 103, and the calculation unit 104. Here, it is assumed that the input I / F 101 supplies color image data including pixel data having signal values of R, G, and B components (signals of three channels of R, G, and B) to each unit.

  The color conversion unit 102 converts color image data including R, G, and B component signal values from pixel data having cyan (C), magenta (M), yellow (Y), and black (K) signal values. To color image data. In other words, the color conversion unit 102 converts color image data composed of signal values of R, G, and B components from color image data composed of signal values of C, M, and Y components and a signal value of black (K). To monochrome image data.

The mixing ratio calculation unit 103 converts R, G, and B component signals (color separation signals) according to the chromaticity of the target pixel. For example, the mixture ratio calculation unit 103 calculates the mixture ratio Pi with respect to Si by the following equation (1), assuming that the signal input for each pixel is Si (i = r, g, b).

  In the above mathematical formula (1), j is r, g, b as in the case of i described above. In addition, the coefficient α in the formula (1) represents a minimum necessary value to be added in order to prevent the 0% exception process. The coefficient α is a minute value that does not affect the value (mixing ratio) obtained by dividing the sum of all components excluding the component for which the mixing ratio is calculated and the sum of all components including the component that produces the mixing ratio. .

According to the formula (1), for example, the mixing ratio of each component is calculated for each value of (R, G, B) as follows.
When R = 0, G = 0, and B = 255, the mixing ratio Pr of the R component is “0.5”, the mixing ratio of the G component is “0.5”, and the mixing ratio of the B component is “0”. Become.
When R = 51, G = 51, and B = 204, the R component mixing ratio Pr is “0.417”, the G component mixing ratio is “0.417”, and the B component mixing ratio is “0.167”. "
When R = 128, G = 128, and B = 128, the R component mixing ratio Pr is “0.333”, the G component mixing ratio is “0.333”, and the B component mixing ratio is “0.333”. "

  In the target pixel for which the mixture ratio Pi is calculated, even when only a specific signal does not change, it is possible to adjust the feature quantity for character identification by reflecting the change in the complementary color signal. The mixing ratio calculation unit 103 supplies the calculation unit 104 with the mixing ratio Pi of each component calculated as described above and the signal value Si of each component.

The calculation unit 104 calculates a value V used for calculating the feature amount from the signal value Si and the mixing ratio Pi by the following formula (2).

  The value V is the sum of values obtained by multiplying the signal value of each component by the mixing ratio of each component. This value V is a luminance equivalent value corresponding to the luminance in the pixel. Therefore, the calculation unit 104 calculates one luminance equivalent value V for each pixel.

  The calculation unit 104 supplies the feature value calculation unit 105 with a value V for calculating the feature value calculated by the mathematical formula (2). The feature amount calculation unit 105 calculates a feature amount indicating a state around the pixel to be identified. The feature amount calculation unit 105 calculates a feature amount for the target pixel using a partial image (operator) having a predetermined size including the pixel to be identified and its peripheral pixels. Here, it is assumed that the feature amount for a certain pixel is a value indicating the state of the difference value around the pixel.

An example of a feature amount calculation method by the feature amount calculation unit 105 will be described.
FIG. 4A and FIG. 4B are diagrams for explaining a feature amount calculation method when the size of the operator is 5 × 5 pixels, respectively. In FIG. 4A and FIG. 4B, the pixel for which the feature amount is obtained is a hatched pixel located at the center of these operators. 4A and 4B show the pixel directions for which the operator obtains the difference.

FIG. 4A shows that the difference between pixels is calculated for each column (vertical direction) of the operator. That is, as shown in FIG. 4A, the feature amount calculation unit 105 obtains an absolute value of a difference between pixels in the main scanning direction for each column. When the absolute value of the difference between pixels for each column is calculated, the feature amount calculation unit 105 obtains the maximum value of the absolute value of the difference in each column. The feature amount calculation unit 105 performs the above processing for all the columns of the operator. When the above processing is executed for all the columns, the feature amount calculation unit 105 obtains an average value of all the columns based on the maximum value of each column. The average value of all the columns is a value indicating a change in the pixel value in the vertical direction of the operator, that is, a value Φmain indicating a change in the pixel value in the main scanning direction. The change value Φmain in the main scanning direction obtained from the difference between the pixels in the vertical direction of the operator as described above can be expressed by the following formula (3).

Further, FIG. 4B shows that a difference between pixels is calculated for each row (horizontal direction) of the operator. That is, as shown in FIG. 4B, the feature amount calculation unit 105 obtains an absolute value of a difference between pixels in the main scanning direction for each row. When the absolute value of the difference between the pixels for each row is calculated, the feature amount calculation unit 105 obtains the maximum absolute value of the difference in each row. The feature amount calculation unit 105 performs the above process on all lines of the operator. When the above processing is executed for all the rows, the feature amount calculation unit 105 obtains an average value of all the rows based on the maximum value of each row. The average value of all the rows is a value indicating a change in the pixel value in the horizontal direction of the operator, that is, a value Φsub indicating a change in the pixel value in the sub-scanning direction. The change value Φsub in the sub-scanning direction obtained from the difference between pixels in the horizontal direction of the operator as described above can be expressed by the following formula (4).

  When the above Φmain and Φsub are calculated, the feature amount calculation unit 105 further detects a portion where the difference value is biased in either the main scanning direction or the sub-scanning direction. Therefore, the feature amount calculation unit 105 obtains the absolute value of the difference between Φmain and Φsub as the feature amount Φ1 of the target pixel.

  The character determination unit 106 compares the feature amount Φ1 calculated by the feature amount calculation unit 105 with a preset first character threshold Th1. That is, when the feature amount Φ1 is supplied from the feature amount calculation unit 105, the character determination unit 106 determines that the pixel is a character image or a line drawing (hereinafter referred to as a character image) if the feature amount Φ1 is equal to or greater than the first character threshold Th1. If the feature quantity Φ1 is less than the first character threshold Th1, it is determined that the pixel is not a character.

Further, the feature amount calculation unit 105 also performs a process of calculating a feature amount for detecting an image of an oblique line to be determined as a character in the input image.
This is because it is difficult to detect an image of an oblique line only by the difference between the vertical direction and the horizontal direction in the partial image (operator) centered on the pixel to be identified.
That is, the feature amount calculation unit 105 supplementarily calculates a feature amount Φ2 for separately detecting pixels constituting a line component around 45 degrees (45 degrees with respect to the vertical and horizontal directions described above). The feature quantity Φ2 used for detecting the pixels constituting the line component of about 45 degrees can be calculated by a method similar to the method for calculating the feature quantity Φ1 described above. However, the feature amount Φ2 is different from the calculation processing of the feature amount Φ1 in terms of the relative position between pixels when taking the difference.

  FIG. 5A and FIG. 5B are diagrams for explaining a method of calculating the feature amount Φ2 in the oblique direction when the size of the operator is 5 × 5 pixels, respectively. In FIG. 5A and FIG. 5B, the pixel for which the feature amount is obtained is a hatched pixel located at the center of the operator, as in FIGS. 4A and 4B.

  FIG. 5A shows that a difference between pixels in a diagonally lower left 45 ° direction (hereinafter also referred to as a dir1 direction) is calculated toward the paper surface. Further, FIG. 5B shows that the difference between pixels in the diagonally lower right 45 ° direction (hereinafter also referred to as the dir2 direction) toward the paper surface is calculated. That is, the feature quantity calculation unit 105 obtains a difference between pixels in the dir1 direction and the dir2 direction, as shown in FIGS.

  When the difference between the pixels is calculated for each arrangement in the dir1 direction illustrated in FIG. 5A, the feature amount calculation unit 105 obtains the maximum absolute value of the differences for each arrangement in the dir1 direction. The feature amount calculation unit 105 obtains the average value Φdir1 from the maximum value of each line in the dir1 direction. The average value Φdir1 is a value Φdir1 indicating a change in pixel value in the 45-degree direction of the operator.

Further, when the difference between the pixels is calculated for each arrangement in the dir2 direction illustrated in FIG. 5B, the feature amount calculation unit 105 obtains the maximum absolute value of the difference for each arrangement in the dir2 direction. The feature amount calculation unit 105 obtains an average value Φdir2 from the maximum value of each line in the dir2 direction. This average value Φdir2 is a value Φdir2 indicating a change in the pixel value in the 45-degree oblique direction of the operator.
When the average value Φdir1 and the average value Φdir2 are calculated, the feature amount calculation unit 105 calculates the absolute value of the difference between Φdir1 and Φdir2 as the target feature amount Φ2.

  The character determination unit 106 also compares the feature amount Φ2 calculated by the feature amount calculation unit 105 with a second character threshold Th2 set in advance. That is, when the feature amount Φ2 is supplied from the feature amount calculation unit 105, the character determination unit 106 determines that the pixel is a character pixel if the feature amount Φ2 is equal to or greater than the second character threshold Th2. If the feature amount Φ2 is less than the second character threshold Th2, it is determined that the pixel is not a character. Note that the second character threshold Th2 applied to the feature amount in the oblique direction and the first character threshold Th1 applied to the feature amount in the vertical and horizontal directions set in advance in the character determination unit 106 are set. .

That is, in the character determination unit 106, when the feature amount Φ1 calculated by the feature amount calculation unit 105 is equal to or larger than the first character threshold Th1, or the feature amount Φ2 calculated by the feature amount calculation unit 105 is the second value. When it is equal to or greater than the character threshold Th2, it is determined that the target pixel is a pixel belonging to a character or line drawing. Further, in the character determination unit 106, when the feature quantity Φ1 is less than the first character threshold value Th1 and the feature quantity Φ2 is less than the second character threshold value Th2, the target pixel belongs to the character or line drawing It is determined that it is not.
Note that the feature amount calculation unit 105 may calculate the feature amount using a method of obtaining a Laplacian other than the above-described method.

  The character determination unit 106 supplies the determination result as described above to the scaling processing unit 107, the filter processing unit 108, and the gradation processing unit 109. The character determination unit 106 outputs a signal (for example, “1”) indicating a character part when the target pixel is a character or a line drawing, and outputs a non-character when the target pixel is a non-character. A signal indicating the part (for example, “0”) is output.

The scaling processing unit 107, the filter processing unit 108, and the gradation processing unit 109, which have received the signal indicating the determination result from the character determination unit 106, switch image processing for each pixel and change the pixel attribute (character Or non-character) to obtain a preferable image.
For example, the scaling processing unit 107 applies linear interpolation that does not decrease the sharpness of characters to pixels determined to be characters (for example, linear interpolation in which weighting is changed for each pixel when enlarging), Simple linear interpolation is applied to pixels determined to be non-characters.
The filter processing unit 108 applies a filter that emphasizes a high frequency to pixels that are determined to be characters, and applies a filter that allows a low frequency to pass to pixels that are determined to be non-characters.
The gradation processing unit 109 applies gradation processing with high contrast that emphasizes sharpness, such as simple binarization, to pixels belonging to characters, and the number of gradations, such as dither or error diffusion, to pixels belonging to non-characters. Apply soft gradation processing with a lot of noise.

  As described above, in the image processing of the first embodiment, by adopting the configuration as described above, it is possible to perform the processing with only one channel for the feature amount calculation unit having a large circuit scale and a large processing load. . Further, in the image processing of the first embodiment, it is possible to use an operator having a larger size than the conventional one so that coarse halftone dots can be detected by reducing the number of channels.

  Furthermore, in the image processing according to the first embodiment having the above-described configuration, the fluctuation of the signal is relatively enlarged as compared with the image processing using one component of the luminance component or multi-channel with a uniform mixing ratio. Can be extracted. For this reason, even when the difference is large only in the signal value for one channel, such as a chromatic character on a white background or an achromatic character on a color background, the first implementation described above. In the image processing of the example, the difference value can be enlarged by adjusting the mixing ratio by the ratio of the complementary color without the difference value being reduced to 1/3. For this reason, in the image processing of the first embodiment, it is possible to easily detect a chromatic character or an achromatic character on a color background.

Next, a second embodiment will be described.
FIG. 6 is a block diagram illustrating a configuration example of the image processing unit 200 as the second embodiment.
In the configuration example illustrated in FIG. 6, the image processing unit 200 includes an input interface (I / F) 201, a color conversion unit 202, a mixture ratio calculation unit 203, a calculation unit 204, a feature amount calculation unit 205, a character determination unit 206, a black ink The printing unit 207, the filter processing unit 208, the gradation processing unit 209, the output interface (I / F) 210, the color determination unit 221 and the like are included.

  The input I / F 201, the color conversion unit 202, the mixture ratio calculation unit 203, the calculation unit 204, the feature amount calculation unit 205, the character determination unit 206, the filter processing unit 208, the gradation processing unit 209, and the output I / F 210 are respectively The input I / F 101, the color conversion unit 102, the mixing ratio calculation unit 103, the calculation unit 104, the feature amount calculation unit 105, the character determination unit 106, the filter processing unit 108, the gradation processing unit 109, and the like described in the first embodiment This can be realized with the same configuration as the output I / F 110. For this reason, detailed description thereof will be omitted.

The color determination unit 221 determines whether the target pixel is a chromatic color or an achromatic color. The color determination unit 221 calculates a value (saturation equivalent value) corresponding to the saturation of the target pixel. The color determination unit 221 determines whether the pixel is a chromatic color or an achromatic color based on the calculated saturation equivalent value. The saturation equivalent value C is obtained by, for example, the following formula (5).

  The color determination unit 221 compares the saturation equivalent value C calculated by Equation (5) with a preset color determination threshold ThC. When the saturation equivalent value C is equal to or greater than the color determination threshold ThC, the color determination unit 221 determines that the pixel is a chromatic color. If the saturation equivalent value C is less than the color determination threshold ThC, the color determination unit 221 determines that the pixel is an achromatic color.

  The character determination unit 206 determines whether the target pixel is a character based on the feature amounts Φ1 and Φ2 supplied from the feature amount calculation unit 205. Similar to the character determination unit 106 described in the first embodiment, the character determination unit 206 performs determination processing using the first character threshold Th1 and the second character threshold Th2 as preset fixed values. realizable.

  However, the character determination unit 206 may perform the determination process using a threshold value that reflects the determination result of the color determination unit 221. For example, for the pixel for which the pixel is determined to be achromatic by the color determination unit 221, the first character threshold Thm1 for achromatic color is set as the first character threshold, and the achromatic color is set as the second character threshold. A second character threshold value Thm2 is set. For the pixel for which the color determination unit 221 determines that the pixel is a chromatic color, the first character threshold value Thc1 for chromatic color is set as the first character threshold value, and the chromatic color is used as the second character threshold value. The second character threshold value Thc2 is set. Thereby, the character determination unit 206 can determine whether or not each pixel is a character with a threshold corresponding to whether each pixel is an achromatic color or a chromatic color.

  In addition to the information indicating whether the character is the result of the character determination as described above, the character determination unit 206 outputs information indicating whether the character is an achromatic character or a chromatic character as an attribute signal. That is, the character determination unit 206 sends an attribute signal indicating whether the target pixel belongs to a non-character, an achromatic character, or a chromatic character to the ink printing unit 207, the filter processing unit 208, and the gradation processing unit 209. Output.

  The black printing unit 207 generates pixels to be printed in monochrome black in order to improve black reproducibility. When the attribute information indicating that the character is an achromatic character is received from the character determination unit 206, the ink printing unit 207 prints the pixel as an achromatic character with good reproducibility. Replace with a value that will result in a black pixel (complete black single color). When the attribute information indicating that the character is a chromatic character is received from the character determination unit 206 or the attribute information indicating that the character is a non-character is received from the character determination unit 206, the ink printing unit 207 displays the pixel. In order to print as chromatic character or non-character with good reproducibility, the rate of converting the pixel into a complete black single color is lowered, or the GCR method is adopted.

Similarly to the filter processing unit 108 of the first embodiment, the filter processing unit 208 applies a filter that emphasizes the high frequency to pixels that are chromatic or achromatic characters. For pixels determined to be characters, a filter process is applied that applies a filter that passes low frequencies. In addition, the gradation processing unit 209 applies a gradation process that makes a hard tone with emphasis on sharpness, such as simple binarization, to pixels belonging to characters for both chromatic and achromatic colors, and applies to pixels belonging to non-characters. For example, soft gradation processing with a large number of gradations such as dither or error diffusion is applied.
Note that in order to adjust the image quality, the filter coefficient of the filter processing in the filter processing unit 208 or the parameter of the gradation processing in the gradation processing unit 209 is the pixel and the achromatic character that are determined to be chromatic characters. It may be different for the pixels determined as.

  In the second embodiment having the above-described configuration, similarly to the first embodiment, the feature amount calculation unit having a large circuit scale and a large processing load can be processed by only one channel. That is, in the second embodiment, since the number of channels is only one, even if a feature amount detection process using a large operator is performed to detect coarse halftone dots or characters with high accuracy, As a whole, the load can be reduced.

  Further, in the image processing of the second embodiment, the fluctuation of the signal can be relatively enlarged and extracted in comparison with the image processing in which the luminance component having a uniform mixture ratio or one signal of the multiple channels is extracted and used. it can. For this reason, in the image processing of the second embodiment, it is possible to detect a chromatic character on a white background or an achromatic character on a color background with high accuracy. Also, in the image processing of the second embodiment, the processing is different for chromatic characters and achromatic characters determined according to the saturation of each pixel, so that it is suitable for each of chromatic or achromatic characters. Can be performed.

Next, a third embodiment will be described.
FIG. 7 is a block diagram illustrating a configuration example of an image processing unit 300 according to the third embodiment.
In the configuration example illustrated in FIG. 7, the image processing unit 300 includes an input interface (I / F) 301, a mixture ratio calculation unit 303, a calculation unit 304, a feature amount calculation unit 305, a character determination unit 306, a filter processing unit 308, a floor. The tone processing unit 309, an output interface (I / F) 310, a color determination unit 321 and the like are included.

  An input interface (I / F) 301, a mixture ratio calculation unit 303, a calculation unit 304, a feature amount calculation unit 305, a character determination unit 306, a filter processing unit 308, a gradation processing unit 309, and an output interface (I / F) 310 , The input I / F 101, the color conversion unit 102, the mixture ratio calculation unit 103, the calculation unit 104, the feature amount calculation unit 105, the character determination unit 106, the filter processing unit 108, and the gradation processing unit described in the first embodiment, respectively. 109 and the output I / F 110. The color determination unit 321 can be realized with the same configuration as the color determination unit 221 described in the second embodiment. For this reason, detailed description on the configuration of these units will be omitted.

  The third embodiment is different from the first and second embodiments in that it is assumed that the image data input to the image processing unit 300 is color image data composed of CMYK components. For example, print data is used as the image data in the CMYK format. That is, the image processing unit 300 of the third embodiment is applied to, for example, an image processing unit that inputs print data and processes the input print data.

In the configuration example illustrated in FIG. 7, the input interface 301 supplies CMYK format image data provided from the input system to the filter processing unit 308, the mixture ratio calculation unit 303, and the color determination unit 321.
In the mixing ratio calculation unit 303, each component of C, M, and Y is set as a calculation target of the mixing ratio Pi, and a fixed value is applied to the K component. The mixing ratio calculation unit 303 replaces the variable “i” from “R, G, B” to “C, M, Y” in the mixing ratio calculation method described in the first embodiment, and applies the mixing ratio. Pi is calculated. That is, the mixture ratio calculation unit 303 calculates the mixture ratio Pi using the formula (1) described in the first embodiment.

The calculation unit 304 calculates the value V by the same method as that of the calculation unit 104 described in the first embodiment. The arithmetic unit 304 is characterized by considering the K component in addition to the “C, M, Y” components corresponding to the “R, G, B” components in the calculation method described in the first embodiment. A value V for calculating the amount is calculated. In other words, the arithmetic unit 304 calculates the value V for calculating the feature value by the following equation (6).

  In the above equation (6), S4 represents the K component of the signal value. The arithmetic unit 304 supplies a value (luminance equivalent value) V calculated using the mathematical formula (6) to the feature amount calculation unit 305. The feature quantity calculation unit 305 calculates the feature quantity Φ1 and the feature quantity Φ2 by using the value V by the same process as in the first embodiment.

In the color determination unit 321, similarly to the color determination unit 221 described in the second embodiment, after obtaining a saturation equivalent value C corresponding to the saturation of the target pixel, Discriminate between chromatic and achromatic colors. The color determination unit 321 calculates the saturation equivalent value C by the following formula (7) using each component of C, M, and Y instead of each component of R, G, and B.

  The color determination unit 321 determines whether the target pixel is an achromatic color or a chromatic color by comparing the saturation equivalent value C with a preset color determination threshold value. That is, the color determination unit 321 determines that the pixel is a chromatic color when the saturation equivalent value C is greater than or equal to the color determination threshold, and if the saturation equivalent value C is less than the color determination threshold, It is determined that the pixel is achromatic.

  The character determination unit 306 is based on the feature amounts Φ1 and Φ2 calculated by the feature amount calculation unit 305 and information indicating whether the target pixel is a chromatic color or an achromatic color. It is determined whether the character is an achromatic character or a chromatic character. The character determination unit 306 outputs an attribute signal indicating whether the target pixel is a non-character, an achromatic color character, or a chromatic color character to the filter processing unit 308 and the gradation processing unit 309 as the determination result.

For example, the filter processing unit 308 applies a filter that emphasizes the high frequency to pixels that are chromatic or achromatic characters as in the first embodiment or the second embodiment. For pixels determined to be non-characters, a filtering process is applied to which a filter that passes low frequencies is applied. In addition, the gradation processing unit 309 applies a gradation process that makes a hard tone with emphasis on sharpness, such as simple binarization, to pixels that are chromatic or achromatic characters, and applies them to pixels belonging to non-characters. On the other hand, soft gradation processing with a large number of gradations such as dither or error diffusion is applied.
In order to adjust the image quality, the filter coefficient of the filter processing unit 308 or the processing parameter of the gradation processing unit 309 includes a pixel determined to be a chromatic character and a character determined to be an achromatic character. Then it may be different.

  By adopting the above-described configuration, in the third embodiment, even if the input image data is a color image in the CMYK format, the circuit scale is large and processing is performed as in the first and second embodiments. The feature amount calculation unit with a large load can be processed by only one channel. Therefore, in the image processing unit of the third embodiment, by reducing the number of channels, it is possible to use an operator having a larger size than the conventional one so as to be able to detect a rough halftone dot. In addition, since it is possible to extract the fluctuation of the signal relatively, rather than extracting and using one signal of luminance components or a multi-channel with a uniform mixing ratio, a chromatic character on a white background, Furthermore, it is possible to detect achromatic characters on the color base. In addition, it is possible to perform processing suitable for each of chromatic color characters and achromatic color characters according to saturation.

  As described above, in the third embodiment, even if the input image data is a color image in the CMYK format, the circuit scale is large and the processing load is large as in the first and second embodiments. The feature amount calculation unit can perform processing for only one channel. That is, in the third embodiment, since the number of channels is only one, even if a feature amount detection process using a large operator is performed to detect coarse halftone dots or characters with high accuracy, As a whole, the load can be reduced.

  Further, in the image processing of the third embodiment, the signal fluctuation can be relatively enlarged and extracted in comparison with the image processing in which the luminance component having a uniform mixing ratio or one signal of the multiple channels is extracted and used. It is also possible to detect a chromatic character on a white background or an achromatic character on a color background with high accuracy. In the image processing of the third embodiment, the processing is different for chromatic characters and achromatic characters that are discriminated according to the saturation of each pixel. Can be performed.

Next, a fourth embodiment will be described.
The fourth embodiment assumes that the image processing by the image processing unit 100 described in the first embodiment is provided as an application program executable by a computer or an extended function of a printer driver. That is, in the fourth embodiment, the flow of processing for realizing image processing similar to the image processing by the image processing unit 100 described in the first embodiment with software will be described.

FIG. 8 is a flowchart for explaining the flow of image processing according to the fourth embodiment.
Each processing shown in FIG. 8 is realized by executing an image processing program stored in a memory by an arithmetic processing unit such as a CPU in a computer, for example. Therefore, in the following description, it is assumed that image processing is realized by an arithmetic processing unit of a computer executing a program.

  The arithmetic processing unit of the computer inputs image data Si (x, y) to be processed through an input interface (not shown) (step S400). Here, x is an integer from an initial value (for example, “1”) to a maximum value (for example, “xw”), and y is an initial value (for example, “1”) to the maximum value (for example, “yw”). It is assumed to be an integer. In this case, the arithmetic processing unit first sets (1, 1) as the initial value of (x, y) (step S401). When (x, y) is initialized (1, 1), the arithmetic processing unit performs discrimination processing on the pixel Si (x, y) with (x, y) as (1, 1) (steps S402 to S408). ).

  That is, the arithmetic processing unit of the computer calculates the mixture ratio Pi (x, y) in the pixel Si (x, y) using the above mathematical formula (1) (step S402). When the mixture ratio Pi (x, y) is calculated, the arithmetic processing unit uses the calculated mixture ratio Pi (x, y) to calculate a feature value (luminance equivalent value) V according to the above equation (2). (X, y) is calculated (step S403).

  When the value V (x, y) is calculated, the arithmetic processing unit represents characteristics with respect to vertical and horizontal components in an image (operator) of a peripheral area having a predetermined size centered on the pixel Si (x, y). A feature quantity Φ1 (x, y) is calculated (step S404). At the same time, the arithmetic processing unit calculates a feature quantity Φ2 (x, y) representing the characteristic of the operator with respect to the oblique component (step S405). When these feature quantities Φ1 (x, y) and Φ2 (x, y) are calculated, the arithmetic processing unit calculates these feature quantities Φ1 (x, y) and Φ2 (x, y) and threshold values Th1 and Th2. Compare (step S406).

  When it is determined that the feature quantity Φ1 (x, y) is greater than or equal to the threshold Th1, or when it is determined that the feature quantity Φ2 (x, y) is greater than or equal to the threshold Th2 (step S406, YES), the arithmetic processing unit , It is determined that the target pixel is a character. In this case, for example, the arithmetic processing unit sets the determination signal value TI (x, y) as a signal indicating the attribute of the pixel to “1” (step S407).

When it is determined that the feature quantity Φ1 (x, y) is less than the threshold value Th1 and the feature quantity Φ2 (x, y) is less than the threshold value Th2 (NO in step S406), the arithmetic processing unit Is determined not to be a character. In this case, for example, the arithmetic processing unit sets a determination signal value TI (x, y) as a signal indicating the attribute of the pixel to “0” (step S408).
Note that the determination signal obtained in step S407 or S408 is stored in a memory (not shown).

  When the determination signal value TI (x, y) is set in step S407 or S408, the arithmetic processing unit determines whether x is the maximum value of the x coordinate (for example, “x = xw”) ( Step S409). When it is determined that x is not the maximum value of the x coordinate (step S409, NO), the arithmetic processing unit increments the value of x (x = x + 1) (step S410). In this case, by setting x to x + 1, the arithmetic processing unit executes the processes of steps S402 to S408 as the determination process for the pixel Si (x + 1, y).

  Further, when it is determined that x is the maximum value of the x coordinate (step S409, YES), the arithmetic processing unit further determines whether y is the maximum value of the y coordinate (for example, “y = yw”). Judgment is made (step S411). If it is determined that y is not the maximum value (step S411, NO), the arithmetic processing unit initializes the value of x (step S412) and increments the value of y (y = y + 1) (step S413). In this case, since x is an initial value (“1”) and y is y + 1, the arithmetic processing unit executes the processes of steps S402 to S408 as the determination process for the pixel Si (1, y + 1). .

  If it is determined that y is the maximum value of the y coordinate (step S411, YES), that is, the determination process for all the pixels from the pixel Si (1, 1) to the pixel Si (xw, yw) is completed. When the determination is made, the arithmetic processing unit outputs a determination signal TI (x, y) as a determination result for all the pixels Si (x, y).

  Image processing according to the above-described processing procedure can be realized by securing a memory area for one channel for use in the feature amount calculation processing. Further, in the image processing of the fourth embodiment, the use area on the memory can be reduced by reducing the number of channels. Therefore, in order to detect a rough halftone dot with high accuracy, an operator (attention for calculating feature values) is used. It is also possible to increase the size of the image area around the pixel. Further, in the image processing of the fourth embodiment, the fluctuation of the signal is relatively enlarged and extracted as compared with the image processing using and extracting the luminance component with a uniform mixing ratio or one signal of multiple channels. It is also possible to detect a chromatic character on a white background or an achromatic character on a color background.

Next, a fifth embodiment will be described.
The fifth embodiment assumes that the image processing by the image processing unit 200 described in the second embodiment is provided as an application program executable by a computer or an extended function of a printer driver. That is, in the fifth embodiment, a flow of processing for realizing image processing similar to the image processing by the image processing unit 200 described in the second embodiment with software will be described.

FIG. 9 is a flowchart for explaining the flow of image processing according to the fifth embodiment.
Each process shown in FIG. 9 is realized by executing an image processing program stored in a memory by an arithmetic processing unit such as a CPU in a computer, for example. Therefore, in the following description, it is assumed that image processing is realized by an arithmetic processing unit of a computer executing a program.

  The arithmetic processing unit of the computer inputs image data Si (x, y) to be processed through an input interface (not shown) (step S500). Here, x is an integer from an initial value (eg, “1”) to a maximum value (eg, “xw”), and y is an integer from an initial value (eg, “1”) to the maximum value (eg, “yw”). Suppose that The arithmetic processing unit first sets (x, y) as an initial value to (1, 1) (step S501). When (x, y) is initialized, the arithmetic processing unit performs a discrimination process on the pixel Si (x, y) (steps S502 to S512).

  That is, the arithmetic processing unit of the computer calculates the saturation equivalent value C (x, y) in the pixel Si (x, y) using the formula (5) described in the second embodiment (step S502). . When the saturation equivalent value C is calculated, the arithmetic processing unit calculates the mixture ratio Pi (x, y) in the pixel Si (x, y) using the above mathematical formula (1) (step S503). When the mixture ratio Pi (x, y) is calculated, the arithmetic processing unit uses the calculated mixture ratio Pi (x, y) to calculate a feature value (luminance equivalent value) V according to the above equation (2). (X, y) is calculated (step S504).

  When the value V (x, y) is calculated, the arithmetic processing unit represents characteristics with respect to vertical and horizontal components in an image (operator) of a peripheral area having a predetermined size centered on the pixel Si (x, y). A feature quantity Φ1 (x, y) is calculated (step S505). At the same time, the arithmetic processing unit calculates a feature quantity Φ2 (x, y) representing a feature with respect to the component in the oblique direction in the operator (step S506).

Here, the arithmetic processing unit determines whether or not the saturation equivalent value C is equal to or greater than the color determination threshold value ThC (step S507).
If it is determined by the above determination that the saturation equivalent value C is equal to or greater than the color determination threshold ThC (step S507, YES), the arithmetic processing unit determines that the pixel is a chromatic color. In this case, the arithmetic processing unit sets the color determination result CM (x, y) as “0” indicating a chromatic color as a signal indicating the attribute of the pixel. Further, when determining that the pixel is a chromatic color, the arithmetic processing unit sets the first character threshold Th1 to the first character threshold Thc1 for chromatic color, and sets the second character threshold Th2 to the first color threshold for chromatic color. 2 is set to the character threshold value Thc2 (step S508).

  If it is determined by the above determination that the saturation equivalent value C is less than the color determination threshold ThC (NO in step S507), the arithmetic processing unit determines that the pixel is an achromatic color. In this case, the arithmetic processing unit sets “1” indicating that the color determination result CM (x, y) is an achromatic color as a signal indicating the attribute of the pixel. Further, when determining that the pixel is an achromatic color, the arithmetic processing unit sets the first character threshold value Th1 to the first character threshold value Thm1 for the achromatic color, and sets the second character threshold value Th2 to the first color threshold value for the achromatic color. The character threshold value Thm2 is set to 2 (step S509).

  The processes in steps S507 to S509 are processes that can be executed after step S502. For example, when the first and second character threshold values are set according to the color determination result, the processes in steps S507 to S509 can be executed at any timing from step S502 to step S510. Moreover, you may make it perform the process of the said step S507-S509 in parallel with the process of step S503-S506.

When the feature quantities Φ1 (x, y) and Φ2 (x, y) are calculated, the arithmetic processing unit calculates these feature quantities Φ1 (x, y) and Φ2 (x, y) and the first character threshold Th1 and The second character threshold value Th2 is compared (step S510).
When it is determined that the feature quantity Φ1 (x, y) is greater than or equal to the first character threshold Th1, or when it is determined that the feature quantity Φ2 (x, y) is greater than or equal to the second character threshold Th2 (step S510). , YES), the arithmetic processing unit determines that the target pixel is a character. In this case, for example, the arithmetic processing unit sets the determination signal value TI (x, y) as a signal indicating the attribute of the pixel to “1” (step S511).

Further, when it is determined that the feature quantity Φ1 (x, y) is less than the first character threshold value Th1 and the feature quantity Φ2 (x, y) is less than the second character threshold value Th2 (step S510, NO). The arithmetic processing unit determines that the pixel is not a character. In this case, for example, the arithmetic processing unit sets the determination signal value TI (x, y) as a signal indicating the attribute of the pixel to “0” (step S512).
In addition, each signal which shows the attribute of the said pixel obtained by step S508, S509, S511, or S512 shall be accumulate | stored in the memory which is not shown in figure.

  When the character determination result for the pixel is obtained, the arithmetic processing unit determines whether x is the maximum value of the x coordinate (for example, “x = xw”) (step S513). When it is determined that x is not the maximum value of the x coordinate (step S513, NO), the arithmetic processing unit increments the value of x (x = x + 1) (step S514). In this case, by setting x to x + 1, the arithmetic processing unit executes the processes of steps S502 to S513 as the determination process for the pixel Si (x + 1, y).

  When x is determined to be the maximum value of the x coordinate (step S513, YES), the arithmetic processing unit further determines whether y is the maximum value of the y coordinate (for example, “y = yw”). Is determined (step S515). When it is determined that y is not the maximum value of the y coordinate (step S515, NO), the arithmetic processing unit initializes the value of x (step S516) and increments the value of y (y = y + 1) (step) S517). In this case, since x is an initial value (“1”) and y is y + 1, the arithmetic processing unit executes the processes of steps S502 to S512 as the determination process for the pixel Si (1, y + 1). .

  Further, when it is determined that y is the maximum value of the y-coordinate (step S515, YES), that is, the determination processing for all the pixels from the pixel Si (1, 1) to the pixel Si (xw, yw) is completed. When the determination is made, the arithmetic processing unit outputs a determination signal TI (x, y) as a determination result for all the pixels Si (x, y) (step S518).

  Image processing according to the above-described processing procedure can be realized by securing a memory area for one channel for use in the feature amount calculation processing. This means that the above-described image processing is suitable for execution by software. Further, in the image processing of the fifth embodiment, the use area on the memory can be reduced by reducing the number of channels. Therefore, an operator (attention for calculating feature values) is used to detect coarse halftone dots with high accuracy. It is also possible to increase the size of the image area around the pixel. Further, in the image processing of the fifth embodiment, the fluctuation of the signal is relatively enlarged and extracted as compared with the image processing in which a luminance component having a uniform mixing ratio or one signal of multiple channels is extracted and used. It is also possible to detect a chromatic character on a white background or an achromatic character on a color background.

  DESCRIPTION OF SYMBOLS 1 ... Digital multifunction device, 10 ... Main control part, 11 ... Scanner, 12 ... Printer, 13 ... Facsimile communication part (FAX part), 14 ... Network communication part, 15 ... Operation part (control panel), 21 ... CPU, 26 ... Output image processing unit, 100, 200, 300 ... Image processing unit, 101, 201, 301 ... Input interface, 102, 202 ... Color conversion unit, 103, 203, 303 ... Mixing ratio calculation unit, 104, 204, 304 ... Arithmetic unit 105, 205, 305 ... feature amount calculation unit 106, 206, 306 ... character determination unit 107, 307 ... scaling processing unit 108, 208, 308 ... filter processing unit 109, 209, 309 ... floor Tone processing unit, 110, 210, 310... Output interface, 207... Black printing unit, 221, 321.

JP 2001-245142 A JP 2007-243330 A

Claims (8)

Input means for inputting image data composed of pixels composed of a plurality of component values;
A mixing ratio calculating unit that calculates a mixing ratio of each component from the value of each component for each pixel in the image data input by the input unit;
Calculating means for calculating a sum of a value obtained by multiplying the calculated mixing ratio by the mixing ratio calculation means and the value of each component for each pixel in the input image data by the input unit as the luminance equivalent value of each pixel,
Character determining means for determining whether each pixel is a pixel belonging to a character image or a line drawing based on the luminance equivalent value calculated by the calculating means;
Image processing means for performing different image processing on the pixels belonging to the character image or line drawing and the pixels not belonging to the character image or line drawing according to the determination result by the character determination means;
An image processing apparatus comprising: The mixing ratio calculating means calculates a value obtained by dividing the sum of the values of all components excluding the component for calculating the mixing ratio by the sum of the values of all the components including the component for calculating the mixing ratio as a mixing ratio of each component. To
The image processing apparatus according to claim 1 , wherein: Input means for inputting image data composed of pixels composed of a plurality of component values;
A mixing ratio calculating unit that calculates a mixing ratio of each component from the value of each component for each pixel in the image data input by the input unit;
And determining color determination means for determining each pixel in the input image data is a chromatic color or some achromatic by said input means,
Arithmetic means for calculating a sum of values obtained by multiplying the value of each component and the mixing ratio calculated by the mixing ratio calculating means for each pixel in the image data input by the input means as a luminance equivalent value of each pixel;
Character determining means for determining whether each pixel is a pixel belonging to a character image or a line drawing based on the luminance equivalent value calculated by the calculating means;
Depending on the determination result by the character determination means and the determination result by the color determination means, the pixels belonging to the chromatic color character image or line drawing, the pixels belonging to the achromatic color character image or line drawing, and the characters belonging to the character image or line drawing. Image processing means for performing different image processing on non-pixels;
An image processing apparatus comprising: Whether the character determination means belongs to a character image or a line drawing based on the luminance equivalent value calculated by the calculation means and the character determination criterion for chromatic color for the image determined to be chromatic by the color determination means And determines whether the image determined to be achromatic by the color determination means belongs to the character image or line drawing based on the luminance equivalent value calculated by the calculation means and the character determination standard for achromatic color To
The image processing apparatus according to claim 3 , wherein: Input image data consisting of pixels consisting of multiple component values,
Calculate the mixing ratio of each component from the value of each component for each pixel in this input image data,
Calculating a sum of a value obtained by multiplying the mixing ratio which is the calculated value of each component for each pixel in the image data the input as the luminance equivalent value of each pixel,
Based on the calculated luminance equivalent value, it is determined whether each pixel is a pixel belonging to a character image or a line drawing,
Depending on the determination result, different image processing is performed on pixels belonging to the character image or line drawing and pixels not belonging to the character image or line drawing.
An image processing method. Input image data consisting of pixels consisting of multiple component values,
Determine whether each pixel in this input image data is chromatic or achromatic,
Calculate the mixing ratio of each component from the value of each component for each pixel in the input image data,
For each pixel in the input image data, a sum of values obtained by multiplying the value of each component and the calculated mixing ratio is calculated as a luminance equivalent value of each pixel,
It is determined whether each pixel is a pixel belonging to a character image or a line drawing based on the calculated luminance equivalent value,
According to this determination result and the determination result of the chromatic or achromatic color, pixels belonging to a chromatic character image or line drawing, pixels belonging to an achromatic character image or line drawing, and not belonging to a character image or line drawing Different image processing is performed for each pixel.
An image processing method. On the computer,
A function of inputting image data composed of pixels composed of multiple component values;
A function of calculating the mixing ratio of each component from the value of each component for each pixel in the input image data;
A function of calculating the sum of values obtained by multiplying the mixing ratio which is the calculated value of each component for each pixel in the image data the input as the luminance equivalent value of each pixel,
A function for determining whether each pixel is a pixel belonging to a character image or a line drawing based on the calculated luminance equivalent value;
A function of performing different image processing on pixels belonging to the character image or line drawing and pixels not belonging to the character image or line drawing according to the determination result;
An image processing program for realizing On the computer,
A function of inputting image data composed of pixels composed of multiple component values;
A function of determining whether each pixel in the input image data is a chromatic color or an achromatic color;
A function of calculating the mixing ratio of each component from the value of each component for each pixel in the input image data;
A function of calculating a sum of values obtained by multiplying the value of each component and the calculated mixing ratio for each pixel in the input image data as a luminance equivalent value of each pixel;
A function of determining whether each pixel is a pixel belonging to a character image or a line drawing based on the calculated luminance equivalent value;
According to this determination result and the determination result of the chromatic or achromatic color, pixels belonging to a chromatic character image or line drawing, pixels belonging to an achromatic character image or line drawing, and not belonging to a character image or line drawing A function of performing different image processing for each pixel;
An image processing program for realizing

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