JP4673920B2 - Image processing apparatus and image processing method - Google Patents

Description

  The present invention relates to an image processing apparatus and an image processing method, and more particularly to an image processing apparatus and an image processing method for outputting a high-quality image from page description information created by an image creation apparatus such as a personal computer.

  Printing of image information created by an application executed on a personal computer or the like is performed by describing output text, graphics, images, etc. in page units, and outputting page description information to an image output device such as a printer. Done. At this time, the page description information is output data to a printer or MFP via a printer controller that develops image data composed of information such as pixel color and shading, and identification data indicating attributes of each pixel of the image data. Transmission to an image output device such as (multi-function peripheral) is generally performed.

  In the image processing of the printer controller, filter processing and gradation processing may be switched for each object depending on the identification signal. However, when focusing attention particularly on the filter processing, it has a natural image attribute to improve the sharpness of the natural image. Edge enhancement may be performed for pixels.

  However, when there is a character on a natural image and the contrast between the character and the background is large, the density around the character decreases due to the adverse effect of edge emphasis. In order to prevent this, white spots are prevented by switching the filter process at the inflection point of the attribute of the identification data generated by the image development unit (see, for example, Patent Document 1).

JP 2002-358516 A

  However, since the identification signal generated from the page description information in the conventional printer controller is common to all color plates, image quality may be deteriorated if the same image processing is performed on all color plates.

  In particular, when the technique described in Patent Document 1 is used, since the processing is switched in common for all color plates, there is a disadvantage that sharpness is reduced around the character.

  For example, when considering a pixel of a black character on the color ground, there is a case where gradation processing is performed with emphasis on resolution in a character portion, and gradation processing is performed with emphasis on gradation in a natural image portion or a drawing portion. In this case, when attention is paid to each of the color plates of cyan, magenta, and yellow, there is a problem in that a portion where gradation processing is switched is seen around the character, and image quality is deteriorated.

  The present invention has been made to solve such a problem, and an object thereof is to provide an image processing apparatus and an image processing method capable of obtaining a high-quality image from page description information.

In order to achieve the above object, an image processing apparatus according to an embodiment includes a plurality of pixels in which an original image represented by the image information includes a text attribute and a graphic attribute from image information described in a page description language. Generating first identification data indicating which of the attributes of the color image and first image data indicating pixels of each color plate obtained by dividing the pixel into a plurality of color plates including a black plate One of the first image data of a color plate other than the black plate among the plurality of color plates related to the image development unit and the pixel indicates a density equal to or higher than a first value for each color plate. When the first image data of the black plate is greater than or equal to a second value, and the first identification data corresponding to the first image data represents the text attribute, other than the black plate as the graphics attribute the color version of the, each color plate An identification signal output unit that outputs second identification data representing the attribute of each pixel, and second image data for each color plate by performing predetermined processing on the first image data based on the second identification data The gist of the present invention is to provide an image processing unit for outputting

  With the above configuration, the image quality of the output image can be improved. In particular, since the optimum image processing can be performed for each color plate in the pixels constituting the character, the image quality of the output image of the character on the background is improved.

  Further, since it is possible to prevent the filtering process from being performed at a location where the density difference is large, white-out image quality degradation does not occur, and the image quality can be improved.

1 is a block diagram illustrating a configuration example of an image output apparatus including an image processing apparatus according to a first embodiment of the present invention. It is a block diagram which shows the structure of the identification signal output part in FIG. 3 is a chart showing the operation of a binarizer 21 in the configuration shown in FIG. 3 is a chart showing an operation of a converter 27 in the configuration shown in FIG. It is a chart which shows an example of the block data of the image signal which line buffer 22a outputs. It is a graph which shows an example of the block data of the binarized identification signal which the line buffer 22b outputs. It is a graph which shows the output of the multiplier 23a. It is a graph which shows the output of the multiplier 23b. It is a block diagram which shows the structure of the identification signal output part in the image processing apparatus concerning the 2nd Embodiment of this invention. 10 is a chart showing the operation of the converter in the identification signal output unit shown in FIG. 9. It is explanatory drawing which illustrates the 1st image data processed by the image processing apparatus concerning 2nd Embodiment, 1st identification data, and 2nd identification data.

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

  FIG. 1 is a block diagram showing a configuration of a first embodiment of an image output apparatus 200 including an image processing apparatus 100 according to the present invention.

  The image processing output device 200 includes an image processing unit 100 including an image development unit 1, an identification signal output unit 2, and an image processing unit 3, and an image output unit 4.

  Output data described in a page description language that is output via the printer driver 302 by application software executed by the CPU 301 in the external personal computer 300 or the like is input to the image development unit 1. Then, the image development unit 1 expands the input page description data, the first image data as bitmap data, and the attributes of each pixel (characters, graphics drawn with lines and surfaces, bitmaps such as natural images) First identification data representing an image) is taken out and output separately. The image developing unit 1 can be an external unit as well as an internal unit as shown here.

  Next, the identification signal output unit 2 receives the first image data and the first identification data, and outputs the second identification data for each color plate based on these.

  Further, the image processing unit 3 performs processing for enhancing an image at the time of printer output. The image processing unit 3 receives the first image data output from the image development unit 1 and the second identification data output from the identification signal output unit 2. For example, the filter coefficient for filter processing Alternatively, processing is performed by switching the gamma correction table for gamma correction according to the second identification data, and the result is output as second image data.

  The image output unit 4 is a print engine that receives the second image data generated by the image processing unit 3 and transfers ink onto paper or the like.

  FIG. 2 is a block diagram showing a configuration of an identification signal output unit used in the image processing apparatus according to the first embodiment of the present invention. In this embodiment, although the technique disclosed in Japanese Patent Laid-Open No. 2002-358516 described above prevents white spots by switching the filter process at the inflection point of the attribute, the process is switched in common for all color versions. Therefore, it solves the problem that sharpness is reduced around the character. The density difference between the character and the background is calculated for each color plate, and the filter processing is switched only for the color plate with the large density difference. This prevents sharpness from decreasing and prevents white spots around characters.

  Referring to FIG. 2, any one of cyan, magenta, yellow, and black image data is input to the line buffer 22a, where several lines are accumulated to form block data. The output is supplied to multipliers 23a and 23b.

  On the other hand, the identification signal is binarized by the binarizer 21, and the output signal is given to the line buffer 22b where it is accumulated for several lines to become block data.

  FIG. 3 is a chart showing the relationship between the input identification signal and the binarized output value A in the binarizer 21. The text and graphic are the output value “0”, and the image is the output value “1”. I understand. This is because the output value is set to “1” only when the identification signal is an image representing a natural image in order to extract the boundary between the image region and other regions.

  The output of the binarizer 21 passes through the line buffer 22b and is then supplied to the multipliers 23b and 23c, and is also inverted and supplied to the multiplier 23a.

  The multiplier 23a multiplies the matrix data between the block data output from the line buffer 22a and the inverted data of the block data output from the line buffer 22b. The adder 24a receives the block data output from the multiplier 23a and calculates the sum of the signal values of the block data. This value represents the sum of the density values of the text area and graphic area.

  The adder 24b receives the inverted data of the block data output from the line buffer 22b and calculates the sum. This value represents the sum of the number of pixels in the text area and the graphic area.

  The output of the adder 24a and the output of the adder 24b are input to the divider 25a, and a quotient obtained by dividing the output value of the adder 24a by the output value of the adder 24b is obtained. This quotient represents the average density value of the text area and graphic area.

  Similarly, the multiplier 23b multiplies the block data output from the line buffer 22a and the block data output from the line buffer 22b by matrix elements. The adder 24c receives the block data output from the multiplier 23b, and calculates the sum of the signal values of the block data. This value represents the sum of the density values of the image area. The adder 24d receives the block data output from the line buffer 22b and calculates the sum. This value represents the sum of the number of pixels in the image area.

  The output of the adder 24c and the output of the adder 24d are input to the divider 25b, and a quotient obtained by dividing the output value of the adder 24c by the output value of the adder 24d is obtained. This quotient represents the average density value of the image area.

  The output of the divider 25a and the output of the divider 25b are input to the subtractor 26, the output of the divider 25b is subtracted from the output of the divider 25a, and the subtraction result is supplied to the converter 27 as the output B.

  The multiplier 23c receives the block data output from the line buffer 22b, and supplies the product of the first identification data corresponding to all the elements of the block data to the converter 27 as an output C. When the output value of the multiplier 23c is “1”, it indicates that the attributes of all the pixels are natural images and there is no switching of the attribute of the identification signal.

  The threshold value Th and the identification signal are further input to the converter 27.

  An output operation example in the converter 27 is shown in FIG. Here, when the relationship between the absolute value | B | of the output value B of the subtractor 26 and the threshold Th is | B |> Th and the output value of the multiplier 23c is “0”, the attribute of the color plate is Since there is an inflection point, if the identification signal is an image, it is converted into a graphic.

  On the other hand, when the relationship between the absolute value | B | of the output value B of the subtractor 26 and the threshold Th is | B | ≦ Th, or the output value of the multiplier 23c is “1”, the color plate Since there is no inflection point of the attribute, the first identification signal is output as it is as the second identification signal. The above processing is similarly performed for each color plate.

  An example of specific processing is shown below. Here, for simplification, the block data is assumed to form a 3 × 3 matrix.

  The block data of the image signal output from the line buffer 22a is as shown in FIG. On the other hand, the binarized identification signal block data output from the line buffer 22b is as shown in FIG.

  The output of the multiplier 23a is shown in FIG. 7 because the data in FIG. 5 is multiplied by the data obtained by exchanging “0” and “1” in the data in FIG. Similarly, the output of the multiplier 23b is shown in FIG. 8 because the data of FIG. 5 is multiplied by the data of FIG.

Therefore, the output of the adder 24a is 220 + 180 + 200 = 600
And the output of the adder 24b is 1 + 1 + 1 = 3
The output of the adder 24c is 32 + 10 + 45 + 20 + 25 + 30 = 162
And the output of the adder 24d is 1 + 1 + 1 + 1 + 1 + 1 = 6
It becomes. Therefore, the output value of the divider 25a is 600 ÷ 3 = 200.
This value represents the density average value in the non-image area. Similarly, the output value of the divider 25b is 162 ÷ 6 = 27.
It becomes. The output value of the subtractor 26 is 200−27 = 173
This value becomes the input B to the converter 27.

  The output of the multiplier 23 c becomes “0” because there is even one “0” data in the output of the line buffer 22 b, and this becomes the input C to the converter 27.

  The threshold value Th can be freely determined. However, for example, if the threshold value Th is 100, the upper condition in FIG. 4 is met and the same signal as the first identification signal is output as the second identification signal. .

  In the present embodiment, filter processing is performed in the image area to improve sharpness. However, the filtering process is not limited to the image area. For example, in order to improve the character reproducibility, the adverse effect of the filtering process can be reduced in the same manner when the filtering process is performed on the text area.

  Next, a second embodiment will be described. The overall configuration of the image processing apparatus according to this embodiment is the same as that in FIG. 1, but only the configuration of the identification signal output unit is different.

FIG. 9 is a block diagram of a configuration example of the identification signal output unit 2 according to the second embodiment of the present invention. Cyan, magenta, yellow, binarizer 1 1a of the image signal of each color of black is input to one end, 11b, 11c, the threshold value T1, T2, T3, T4, respectively are inputted to the other end of 11d ing. Here, threshold values T1, T2, and T3 used for binarization are set to T1≈0, T2≈0, and T3≈0, respectively. The threshold value T4 for black binarization is set to T4≈100%. That is, when the output of the binarizer 11d is “1”, it indicates a black object.

Binarizing unit 1 1a, 11b, the output of 11c are input to the OR circuit 12, outputs of the binarizing unit 11d of the OR circuit 12 is inputted to the AND circuit 13

Here, when the output of the OR circuit 12 is “1”, it indicates a color background, and when it is 0, it indicates a white background. Further, when the output of the AND circuit 13 is “1”, it indicates a black object on the color ground, and when it is “0”, it indicates that it is not.

  The converter 14 outputs second identification data indicating the attribute of each pixel for each color plate. This second identification data represents the content of gradation processing to be performed in the subsequent image processing unit. In the case of text, gradation processing is performed with emphasis on resolution, and in the case of graphics and images, emphasis is placed on gradation. Gradation processing is performed.

Figure 10 is a table showing the state of conversion in the converter 1 4, output the identification data text of the AND circuit 13, graphics, by whether it is a image, output color plates is the second identification data Shows how it is set. According to FIG. 10, when the output of the AND circuit 13 is “0”, that is, when it is not a black object on the color ground, the second identification data is exactly the same as the first identification data for each color plate. A pixel whose first identification signal is “text” performs gradation processing with emphasis on resolution, and a pixel of “graphic” or “image” performs gradation processing with emphasis on gradation.

  On the other hand, when the output of the AND circuit is “1”, that is, for black pixels on the color ground, when the first identification data is text, the second identification data is black only text and the other color versions are graphic. It has become. As a result, gradation processing with emphasis on gradation is performed for the cyan, magenta, and yellow color plates, and gradation processing with emphasis on resolution is performed on the black color plate.

  FIG. 11 is an explanatory diagram showing examples of first image data, first identification data, and second identification data. Here, the case where the black letter “A” is drawn on the magenta background, ie, the case where the output of the AND circuit 12 is 1 and the identification data is text in FIG. In the image data, it can be seen that the magenta color plate (FIG. 11 (b)) has the data in the portion of the character “A” in the black color plate (FIG. 11 (d)).

  The first identification data indicates the attribute of each pixel of the first image data in which black characters exist on such a drawing background. The white part of the first identification data indicates a non-text “drawing figure”, and the shaded part indicates a “character” of the text.

  The second identification data gives an attribute to each color plate. That is, cyan (FIG. 11 (f)), magenta (FIG. 11 (g)), and yellow (FIG. 11 (h)) are non-text graphics or images, and black (FIG. 11 (i)). This is similar to the first identification data in which text characters are present on a non-text background.

  As described above, according to this embodiment, the first identification data and the first image data are used to generate the second identification data indicating the attribute of each pixel for each color plate. Switching of gradation processing can be avoided as much as possible, and image quality can be improved.

  In particular, in the case of a character on the background, optimal image processing can be performed for each color plate in the pixels constituting the character, so that the image quality of the output image can be improved.

  In the image processing apparatus described above, the case of four-color printing has been illustrated, but the present invention can be similarly applied to an image forming apparatus that uses more ink, for example, six-color ink.

  In addition, in an output device capable of color printing, the present invention can be applied to various serial type image forming apparatuses such as ink jet and bubble jet (registered trademark).

  Furthermore, if the target device also has a serial image output device, it includes not only a printer but also a color fax machine, a multifunction machine, and the like.

  Further, the image developing unit is not limited to the one built in the image processing apparatus and the image output apparatus, but can be applied to an external printer controller.

DESCRIPTION OF SYMBOLS 1 Image expansion part 2 Identification signal output part 3 Image processing part 4 Image output part 21 Binarizer 22a, 22b Line buffer 23a, 23b, 23c Multiplier 24a, 24b, 24c, 24d Adder 25a, 25b Divider 26 Subtraction 27 Converter 100 Image processing device 200 Image output device 300 Computer 301 CPU
302 Printer driver

Claims (5)

A first identification indicating which attribute of a plurality of attributes including a text attribute and a graphic attribute is included in a pixel constituting the original image represented by the image information from the image information described in the page description language An image development unit for generating data and first image data representing pixels for each color plate obtained by dividing the pixels into a plurality of color plates including a black plate;
Among the plurality of color plates related to the pixel, any one of the first image data of a color plate other than the black plate indicates a density equal to or higher than a first value for each color plate, and the black plate related to the pixel When the first image data is greater than or equal to a second value and the first identification data corresponding to the first image data represents the text attribute, a color plate other than a black plate is selected as the color plate. An identification signal output unit that outputs second identification data representing an attribute of each pixel for each color plate as a graphic attribute;
An image processing apparatus comprising: an image processing unit that performs predetermined processing on the first image data based on the second identification data and outputs second image data for each color plate.   The image processing apparatus according to claim 1, wherein the image processing unit changes a filter coefficient for filter processing applied to the first image data based on the second identification data.   The image processing apparatus according to claim 1, wherein the image processing unit switches a gamma correction table for gamma correction to be applied to the first image data based on the second identification data.   The image processing unit performs gradation processing different when the second identification data indicates a text attribute and when the second identification data indicates a graphic attribute. Image processing apparatus. A first identification indicating which attribute of a plurality of attributes including a text attribute and a graphic attribute is included in a pixel constituting the original image represented by the image information from the image information described in the page description language Data and first image data representing a pixel for each color plate obtained by dividing the pixel into a plurality of color plates including a black plate,
Among the plurality of color plates related to the pixel, any one of the first image data of a color plate other than the black plate indicates a density equal to or higher than a first value for each color plate, and the black plate related to the pixel When the first image data is greater than or equal to a second value and the first identification data corresponding to the first image data represents the text attribute, a color plate other than a black plate is selected as the color plate. As the graphic attribute, generate second identification data representing the attribute of each pixel for each color plate,
An image processing method comprising: performing a predetermined process on the first image data based on the second identification data to generate second image data for each color plate.

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