JP4946370B2 - Image processing apparatus, image forming apparatus, and program - Google Patents

Description

  The present invention relates to an image processing apparatus, an image forming apparatus, and a program for controlling them.

  2. Description of the Related Art Conventionally, a technique for forming / displaying an image obtained by combining a plurality of images in various modes in an image forming apparatus such as a printer is known. For example, it may be a case where a new image is synthesized with a partial area of the background image, or a character or symbol is superimposed on a normal image. In that case, image processing is performed in which the images are combined and displayed in accordance with a predetermined mixing ratio in the region to be combined or overlapped. Such image processing is generally called “alpha blend processing”. (For example, refer to Patent Document 1, Patent Document 2, and Patent Document 3).

In the image processing apparatus and the like disclosed in Patent Document 1, when a rendering engine receives a predetermined command and object information, the rendering engine determines object synthesis processing. If there is an instruction to synthesize an object, the composition is performed by an AND process by an alpha blend operation of the source and destination.
Further, in the image forming apparatus of Patent Document 2, it is determined whether or not there is an indefinite region of an attribute that occurs when objects having different attributes overlap on the print screen. If it exists, the entire attribute bitmap image is changed to a single attribute. If it is determined that there is no indefinite area, the attribute obtained by rendering is used as it is.
Furthermore, in the image forming apparatus of Patent Document 3, when the source pixel and the destination pixel are subjected to a drawing logical operation in the drawing plane, the attribute information of the source pixel is validated in the information plane. Then, when performing a drawing logical operation on the pattern pixel, the source pixel, and the destination pixel in the drawing plane, the attribute information of the source pixel is validated in the information plane. Further, when a mask pixel, a pattern pixel, a source pixel, and a destination pixel are drawn logically in the drawing plane, in the information plane, the attribute information of the source pixel is validated for the portion where the mask pixel is a black pixel, and the white pixel For the portion, the attribute information of the destination pixel is validated.

JP 2001-189841 A (page 3-5, FIG. 5) Japanese Patent Laid-Open No. 2002-312141 (page 7-9, FIG. 2) JP-A-2004-243568 (page 3-7, FIG. 2)

  The present invention has been made in order to cope with the above-described situation, and an object thereof is to form an image synthesized in accordance with a predetermined mixing ratio with high quality.

  For this purpose, in the image processing apparatus of the present invention, for each of a plurality of image elements having a predetermined attribute synthesized according to a predetermined mixing ratio, receiving means for receiving image information including information on the mixing ratio; Regarding a region where a plurality of image elements overlap, based on the pixel value information included in the image information, a calculation unit that calculates a value related to the density according to the mixing ratio of each of the plurality of image elements, and a density calculated by the calculation unit Setting means for setting an attribute of an image element in a region where a plurality of image elements overlap based on a value.

  In addition, as such an image processing apparatus, the image processing apparatus further includes storage means for storing coefficients set individually for the attributes of the image elements, and the calculation means stores the coefficients based on the attributes of the plurality of image elements to be combined. The value related to the density in the region where the plurality of image elements overlap is corrected by the coefficient read from the means, and the setting means sets the attribute of the image element in the area based on the value related to the density corrected by the calculation means, and the setting means The image processing according to the attribute of the image element set by is performed.

  Furthermore, as such an image processing apparatus, the setting means compares values relating to the density of each pixel in a region where a plurality of image elements overlap, and determines the attribute of the image element determined to have a large value as the image element for each pixel. And the image processing corresponding to the attribute of the image element set by the setting means is performed for each pixel.

  On the other hand, the present invention can also be understood as an image forming apparatus. In this case, in the image forming apparatus according to the present invention, for each of a plurality of image elements having a predetermined attribute synthesized according to a predetermined mixing ratio, receiving means for receiving image information including information on the mixing ratio, and the receiving means Image processing means for combining received image information, and image forming means for forming a plurality of image elements combined on a recording medium based on the image information combined by the image processing means. And a calculation unit that calculates a value related to the density according to the mixing ratio of each of the plurality of image elements based on the pixel value information included in the image information with respect to a region where the plurality of image elements overlap. A setting unit configured to set an attribute of an image element in an area where a plurality of image elements overlap based on a value related to density calculated by the calculation unit. Can.

  In addition, as such an image forming apparatus, the image processing unit further includes a storage unit that stores coefficients individually set for the attributes of each image element, and the calculation unit includes a plurality of image elements to be combined. The value related to the density in the region where the plurality of image elements overlap is corrected by the coefficient read from the storage unit based on the attribute, and the setting unit determines the attribute of the image element in the region based on the value related to the density corrected by the calculation unit. It is possible to set and perform image processing according to the attribute of the image element set by the setting unit.

  Further, as such an image forming apparatus, the image processing unit compares the value regarding the density for each pixel in the region where the setting unit overlaps the plurality of image elements, and determines the attribute of the image element determined to have a large value as the pixel. It can be set as an attribute of each image element, and image processing corresponding to the attribute of the image element set by the setting unit is performed for each pixel.

  On the other hand, the present invention can also be understood as a program for controlling the image processing apparatus and the image forming apparatus. In this case, with respect to each of a plurality of image elements having a predetermined attribute synthesized according to a predetermined mixing ratio, an acquisition function for acquiring image information including information on the mixing ratio, and a region where the plurality of image elements overlap A calculation function for calculating a value related to density according to a mixing ratio of each of a plurality of image elements based on pixel value information included in the image information, and a plurality of image elements based on values related to the density calculated by the calculation function And a setting function for setting the attribute of the image element in the region where the two overlap.

  Further, as such a program, the calculation function reads a coefficient based on attributes of a plurality of image elements to be combined from a storage unit in which coefficients individually set for the attributes of each image element are stored. The value related to the density in the region where a plurality of image elements are overlapped by the coefficient, and the setting function sets the attribute of the image element in that region based on the value related to the density corrected by the calculation function, and the image element set by the setting function It is possible to perform image processing according to the attribute of the image.

  Further, as such a program, the setting function compares the values related to the density for each pixel in the region where the plurality of image elements overlap, and determines the attribute of the image element determined to have a large value as the attribute of the image element for each pixel. The image processing according to the attribute of the image element set by the setting function is performed for each pixel.

According to the first aspect of the invention, compared with the case where the invention of the first aspect is not adopted, the composite image is processed so as to be a higher quality image in which the attribute is set based on the density information. can do.
According to the second aspect of the present invention, pixel attribute determination can be controlled in more detail and image quality deterioration due to attribute switching can be reduced as compared with the case where the invention of the second aspect is not adopted. .
According to the invention of claim 3, it is possible to process the representation of each pixel of the composite image so as to have a higher quality than when the invention of claim 3 is not adopted.

According to the invention of claim 4, compared with the case where the invention of claim 4 is not adopted, the synthesized image forms a higher quality image in which the attribute is set based on the information on the density. be able to.
Further, according to the invention of claim 5, as compared with the case where the invention of claim 5 is not adopted, pixel attribute determination can be controlled in more detail, and image quality deterioration due to attribute switching can be reduced. .
Furthermore, according to the invention of claim 6, compared with the case where the invention of claim 6 is not adopted, it is possible to form a composite image in which the expression for each pixel becomes higher quality.

According to the seventh aspect of the invention, compared to the case where the invention of the seventh aspect is not adopted, the synthesized image is a higher quality image in which the attribute is set based on the information on the density. Can be processed.
Further, according to the invention of claim 8, compared with the case where the invention of claim 8 is not adopted, pixel attribute determination can be controlled in more detail, and image quality deterioration due to attribute switching can be reduced. .
Furthermore, according to the ninth aspect of the present invention, it is possible to process the representation of each pixel of the composite image so as to have a higher quality than when the invention according to the ninth aspect is not adopted.

(Detailed description of the image forming apparatus)
DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention (hereinafter referred to as “embodiments”) will be described in detail with reference to the accompanying drawings.
FIG. 1 is a block diagram illustrating an example of a configuration of an image forming apparatus including an image processing apparatus to which the exemplary embodiment is applied. An image forming apparatus 1 illustrated in FIG. 1 is, for example, a digital color printer, and an image processing unit (image processing apparatus) 10 serving as an image processing unit that performs predetermined image processing on image information input from an external device. It has. A secondary storage unit 20 realized by, for example, a hard disk (Hard Disk Drive) in which a processing program or the like is recorded, and a control unit 30 that controls the operation of the entire image forming apparatus 1 are provided. In addition, an image forming unit 40 that forms an image corresponding to the image information of each color component is provided. The image forming unit 40 can use other image forming methods such as an electrophotographic method and an ink jet method.

Next, the image processing unit 10 includes a receiving unit 11 as an image information receiving unit that receives image information from an external device such as a personal computer (PC) 3 or an image reading device 4 such as a scanner. An input buffer 12 that temporarily stores image information received by the receiving unit 11 and a PDL analysis unit 13 that analyzes image information in a PDL (Page Description Language) format are provided. The image processing unit 10 also includes a rendering processing unit 14 that develops (renders) the image information analyzed by the PDL analysis unit 13 into raster image information. Here, the raster image information refers to image information for printing expressed by an array of pixels.
Further, the image processing unit 10 performs color conversion of raster image information into color system (for example, YMCK) image information suitable for printing processing, and an intermediate buffer 15 used as a work area in rendering processing by the rendering processing unit 14. And a color conversion processing unit 16 for performing the processing. A screen processing unit 17 that performs screen processing on the color-converted raster image information is provided.

The receiving unit 11 receives image information and a drawing command from an image reading device 4 such as a user's personal computer (PC) 3 or a scanner.
Then, the image information is output to the input buffer 12, and the drawing command is output to the PDL analysis unit 13. Here, the image information includes, for example, a pixel value, an attribute of the image element, and an alpha value. Here, the pixel value is, for example, a value for each pixel expressed in a predetermined color space, and is expressed by a predetermined gradation, for example. Specifically, for example, data belonging to the sRGB color space expressed by gradation of 8 bits (1 byte) for each RGB. RGB means three primary colors of light composed of R (red), G (green), and B (blue).
The attribute of the image element (hereinafter simply referred to as “attribute”) is information indicating the type of image such as “character”, “graphic”, “photo”, and the like. The alpha value represents the transparency of the corresponding pixel, and the ratio is expressed by, for example, 8 bits (1 byte).

The input buffer 12 temporarily holds the image information input from the reception unit 11 and outputs the image information to the PDL analysis unit 13. The PDL analysis unit 13 creates image information for one print page, for example, according to the analysis result of the image information acquired from the input buffer 12 according to the drawing command. Then, the PDL analysis unit 13 outputs the created image information to the rendering processing unit 14.
The rendering processing unit 14 performs a rendering process on the image information acquired from the PDL analysis unit 13 according to the drawing command. In this rendering process, the rendering processing unit 14 performs a process of synthesizing an image according to a predetermined mixing ratio with respect to the pixel value and the alpha value included in the image information of the synthesis target (source and destination), that is, an alpha blending process. .

Here, the source refers to an image on the side to be synthesized at the time of image formation, that is, an upper image when alpha blend processing is performed. In addition, the destination refers to a side image, that is, a base image, which is synthesized at the time of image formation when alpha blend processing is performed.
The alpha blending process is a process of translucent synthesis using a predetermined mixing ratio, that is, an alpha value in a region where a source and a destination overlap. The alpha value is a value used in an operation for performing the alpha blending process and indicates the transparency of the image, and is a value that each pixel has. When the alpha value is “0”, the case is completely transparent, and when the alpha value is “1”, the case is not transparent at all.

  In addition, in the rendering process, the rendering processing unit 14 acquires the pixel value, the attribute, and the alpha value included in the image information of the source when the source and the destination are alpha blended. Further, the coefficient corresponding to the attribute of the source is read from the secondary storage unit 20. Then, using the acquired alpha value and pixel value, a value relating to the density of the source and destination is calculated. Alternatively, a correction value related to the source and destination densities is calculated using the acquired pixel value, alpha value, and read coefficient. Then, the rendering processing unit 14 sets an attribute of an area where image elements subjected to alpha blend processing overlap based on the comparison result of the calculated density-related value or the density-related correction value, and adds the attribute to the image information. Therefore, the rendering processing unit 14 has both a function as a calculation unit (calculation unit) that calculates a value related to density and a function as a setting unit (setting unit) that sets an attribute. Further, as described above, the secondary storage unit 20 has a function as a coefficient storage unit (storage unit).

Here, the value relating to the density is a value expressing the darkness of the image displayed on the display or the density of the image printed on the medium, for example, a value obtained by calculating an alpha value and a pixel value. be able to. Specifically, for an RGB color space image that has been gamma corrected,
K =
0.299 × (1-R) + 0.587 × (1-G) + 0.114 × (1-B) (1)
It can be calculated with However, since it is not necessary to calculate strictly, for example, it can be simplified and calculated as DK = 3.0−R−B−G. On the other hand, if the color space is different, the calculation formula needs to be changed according to the color space. For this reason, hereinafter, an expression for calculating a value related to density from the pixel value is
K = Dk (pixel value) (2)
Is written.

Then, by multiplying the value related to the density by a coefficient (weighting) based on the attribute of the image, a correction value related to the density can be obtained.
As a result, the rendering processing unit 14 generates raster image information including, for example, pixel values and alpha values that have been subjected to alpha blending processing, and set attributes. Then, the rendering processing unit 14 outputs the raster image information to the color conversion processing unit 16.

  The color conversion processing unit 16 performs color conversion processing on the received raster image information into color information (for example, YMCK) image information suitable for printing processing in the image forming unit 40, and outputs it to the screen processing unit 17. . Here, the color conversion processing unit 16 performs color conversion processing using a different color conversion coefficient for each attribute. The plurality of color conversion coefficients are, for example, a plurality of conversion table data of a table lookup method, and are held in, for example, the secondary storage unit 20. Thereby, the color conversion processing unit 16 can recognize the attribute included in the raster image information from the rendering processing unit 14 and can perform optimum color conversion according to the attribute.

  The screen processing unit 17 performs screen processing on multi-value raster image information for each color component (YMCK) input from the color conversion processing unit 16. Thereby, based on raster image information which is multi-value image information having density gradation, binarized image information (1 bit) representing the density of a halftone image in a pseudo manner by the size of colored dots called halftone dots. Image information).

The screen processing unit 17 can recognize the attribute included in the raster image information from the rendering processing unit 14 and can perform optimal screen processing for each image using the screen parameter set for each attribute. The screen parameter is a parameter for creating a screen, and controls a screen pattern, a screen line width, a screen pitch, a screen angle, and the like. The screen parameters are held for each attribute in the secondary storage unit 20, for example.
Then, the screen processing unit 17 outputs the generated binarized image information to a laser exposure device (not shown) of the image forming unit 40.

(Detailed description of the image processing apparatus)
FIG. 2 is a block diagram illustrating the internal configuration of the image processing unit 10 of this embodiment. As shown in FIG. 2, the image processing unit 10 includes a CPU 101 that executes digital arithmetic processing according to a predetermined processing program when processing image information. A RAM 102 used as a working memory of the CPU 101 and a ROM 103 that stores processing programs executed by the CPU 101 are provided. When the CPU 101 reads this processing program when the image forming apparatus 1 is started up, each function in the image processing unit 10 of the present embodiment is realized. These functions include the above-described image information reception function, image information creation function, rendering processing function, color conversion processing function, gradation correction function, and screen processing function. In addition, a non-volatile memory 104 such as an SRAM or flash memory backed up by a battery, which can be rewritten and can retain data even when power supply is interrupted, is provided. Further, an interface unit 105 that controls input / output of signals to / from each unit such as the PC 3, the secondary storage unit 20, and the image forming unit 40 connected to the image processing unit 10 is provided. The secondary storage unit 20 (see FIG. 1) holds, for example, coefficients, color conversion coefficients, screen parameters, and the like.

(Description of image data to be combined)
FIG. 3A is a diagram illustrating an example of image information (pixel value, attribute, alpha value) of an image to be combined. FIG. 3C is a diagram illustrating an example of the relationship between attributes and coefficients included in image information.
In the example of FIG. 3A, the images synthesized by the alpha blending process are three images (image elements) A, B, and C. The pixel value of the image A is Da (n). Similarly, the pixel value of the image B is Db (n), and the pixel value of the image C is Dc (n). Here, n represents the nth pixel of each image, and indicates that the image is represented by a set of pixels. In the following description, the notation of (n) may be omitted. In this case, it is assumed that each pixel is subjected to arithmetic processing.
The attribute of the image A is “photograph” and the alpha value is “αa (n)”. The attribute of the image B is “graphic”, and the alpha value is “αb (n)”. The attribute of the image C is “character”, and the alpha value is “αc (n)”.

  Here, in the example of FIG. 3A, there are three images having different attributes. However, this is merely an example, and there may be two or four or more images to be combined.

  In addition, images having the same attribute may be combined. For example, in FIG. 3, the attributes of the image A and the image B may both be “photographs”. Furthermore, a composite image generated in the middle of image processing may be image data having different attributes for each pixel.

  The alpha value of each image is set for each pixel or image element. Therefore, in this example, the alpha value of the image C of the image A and the image B is different for each pixel and the transparency can be changed in the image. However, depending on the image, the alpha value is constant in the image and is constant for each pixel. May not have a value. In this case, processing is performed assuming that the alpha values of the images have the same value.

  FIG. 3B is a diagram illustrating an example of image information (pixel value, alpha value) for each pixel of the image A to be combined. In this example, an image to be synthesized is composed of N pixels, and each pixel is expressed in a gradation of 8 bits (1 byte) for each RGB in the sRGB color space. The alpha value is 8-bit data.

  Here, in the example of FIG. 3B, the image information for each pixel is composed of a pixel value and an alpha value, but this is only an example, even if only the pixel value, the pixel value, the alpha value, and the attribute value are used. Good. In addition, the pixel value, the alpha value, and the attribute value need not be arranged together. Further, the pixel values may be different color spaces. Also, the gradation value need not be 3 bytes.

  FIG. 3C shows an example of image element attributes and coefficients used in processing. When the attribute is “photo”, the coefficient is “Cp”. When the attribute is “graphic”, the coefficient is “Cg”. Further, when the attribute is “character”, the coefficient is “Ct”. The specific contents of the calculation will be described later.

(Example of rendering processing)
Next, processing for superimposing images (image elements) in the rendering processing in the rendering processing unit 14 (see FIG. 1) will be described.
FIG. 4 is a flowchart illustrating an example of a rendering process performed by the rendering processing unit 14 (see FIG. 1). Note that the operation example described below shows a rendering process procedure in the case of superimposing images A (see FIG. 3A) as a destination and images C (see FIG. 3A) as a source.

First, the rendering processing unit 14 acquires a drawing command from the PDL analysis unit 13 (see FIG. 1) (step 101). Further, the rendering processing unit 14 acquires image information (pixel value, attribute, and alpha value) about the image elements of the image A and the image C generated by the PDL analysis unit 13, and the intermediate buffer 15 (FIG. 1). (See step 102). Next, the rendering processing unit 14 reads the image information of the image C (source) from the intermediate buffer 15 based on the drawing command (step 103). Subsequently, the rendering processing unit 14 determines whether the drawing command is an alpha blend drawing command or an overwrite drawing command (step 104).
When it is determined in step 104 that the drawing command is an alpha blend drawing command, the rendering processing unit 14 reads out image information of the image A (destination) from the intermediate buffer 15 based on the drawing command (step 105).

Then, the rendering processing unit 14 performs alpha blend processing on the image information of the destination and the source (step 106). In this alpha blending process, an alpha blending operation is performed on the pixel values and alpha values included in each piece of image information (see FIG. 3). The specific contents of this alpha blend calculation will be described later.
Next, the rendering processing unit 14 compares the value of the source density for each pixel in the region where the source and the destination overlap with each other according to the result of comparing whether the value is higher than the value related to the destination density of the pixel. Are determined (step 107). A specific procedure for determining the attribute for each pixel in the region where the image elements (source and destination) overlap will be described later.
Then, the intermediate buffer 15 holds the raster image information obtained by adding the attribute determined in step 107 to the result of the alpha blend operation in step 106 (step 108). Then, it is determined whether or not all drawing commands have been completed (S110). If it is determined that the process has been completed, the process proceeds to step 111 (described later). If it is determined that the process has not been completed, the process returns to step 101 again.

On the other hand, when it is determined in step 104 that the drawing command is an overwrite drawing command, the rendering processing unit 14 uses the image C of the image C with respect to the image information of the image A that is the destination held in the intermediate buffer 15. The image information is overwritten (step 109). Specifically, the pixel value, the attribute, and the alpha value for the region where the ground and the ground overlap each other are determined as the pixel value, the attribute, and the alpha value of the image C. Then, it progresses to step 110.
Then, the rendering processing unit 14 sends the raster image information held in the intermediate buffer 15 to the color conversion processing unit 16 (see FIG. 1) (step 111), and ends the processing. The color conversion processing unit 16 sends the raster image information to the screen processing unit 17 (see FIG. 1) after color conversion.

  The color conversion processing unit 16 selects a color conversion coefficient to be used in the color conversion processing for each pixel (YMCK) according to the attribute determined in step 107 or step 109. Further, the screen processing unit 17 selects a screen parameter used in the screen processing for each pixel (YMCK) according to the attribute determined in step 107 or step 109.

(Example in which attributes of a region where a plurality of image elements overlap are set for each pixel)
Next, specific processing in step 107 (see FIG. 4) will be described.
FIG. 5 is an example of a flowchart showing a part (step 107) of the rendering process in the rendering processing unit 14 (see FIG. 1). First, the rendering processing unit 14 grasps each attribute from the source and destination image information read from the intermediate buffer 15 (see FIG. 1). Further, the rendering processing unit 14 grasps the pixel value and the alpha value for each pixel from the read image information of the source and the destination (Step 201).

Next, the rendering processing unit 14 calculates a value related to the source density for each pixel in a region where the ground and the background overlap, and a value related to the destination density in the pixel (step 202). A method for calculating values related to these densities will be described later. Subsequently, the rendering processing unit 14 determines whether the value related to the source density calculated in step 103 (see FIG. 4) is larger than the value related to the destination density calculated together with the value related to the source density (see FIG. 4). Step 203).
If it is determined in step 203 that the value related to the source density is larger than the value related to the destination density, the rendering processing unit 14 selects an attribute of the source (step 204). When it is determined in step 203 that the value related to the source density is smaller than the value related to the destination density, the rendering processing unit 14 selects a destination attribute (step 205).

  Subsequently, the rendering processing unit 14 adds the selected attribute to the result of the alpha blend operation performed in step 106 (see FIG. 4) (step 206). Then, the process ends.

(Another embodiment in which attributes of a region where a plurality of image elements overlap are set for each pixel)
Next, another example of specific processing in step 107 (see FIG. 4) will be described.
FIG. 6 is another example of a flowchart showing a part (step 107) of the rendering process in the rendering processing unit 14 (see FIG. 1). First, the rendering processing unit 14 grasps each attribute from the source and destination image information read from the intermediate buffer 15 (see FIG. 1). Further, the rendering processing unit 14 grasps the pixel value and the alpha value for each pixel from the read image information of the source and the destination (Step 301).

Next, the rendering processing unit 14 acquires a coefficient (see FIG. 3) corresponding to the attribute of the source (step 302). This coefficient is held in, for example, the secondary storage unit 20. Subsequently, the rendering processing unit 14 calculates a correction value related to the source density for each pixel in a region where the ground and the background overlap and a correction value related to the density of the destination in the pixel using coefficients ( Step 303). A method for calculating the correction values regarding these densities will be described later.
Steps 304 to 307 are the same as steps 203 (see FIG. 5) to step 206 (see FIG. 5), and a description thereof will be omitted. Then, the process ends.

(Setting example of attributes given to the area that has been alpha blended)
Next, attributes given to the area subjected to alpha blend processing will be described.
FIG. 7 is a diagram illustrating an example of a state in which an attribute is set by the image processing unit (image processing apparatus) 10. Here, a composite image in which three images of an image A in the shape of a rectangle 51, an image B in the shape of an ellipse 52, and an image C in the shape of a character A53 are overlapped and synthesized. Is shown. In the example of FIG. 7, the image A, the image B, and the image C are the images described in FIG. 3, and the pixel values, attributes, and alpha values described in FIG. Therefore, the image A is an image having an attribute “photo”, the image B is an image having an attribute “graphic”, and the image C is an image having an attribute “character”.

  The area 54 is an image area only for the image A, the area 55 is an image area only for the image B, and the area 56 is an image area only for the image C. An area 57 is an area where the image elements of the image A and the image C overlap, an area 58 is an area where the image elements of the image A and the image B overlap, and an area 59 is an image element of the image B and the image C. Is the area where. A region 60 is a region where the image elements of the image A, the image B, and the image C overlap. In the example of FIG. 7, the image A is the lowest layer, the image C is overlaid there, and finally the image B is overlaid.

  First, attributes in the region 54, the region 55, and the region 56 will be described. These image areas are areas where image elements do not overlap. Therefore, the alpha blend process is not performed, and the attribute of the region 54 is “photograph” (see FIG. 3). The attribute of the area 55 is “graphic” (see FIG. 3), and the attribute of the area 56 is “character” (see FIG. 3).

  Next, attributes in the region 57, the region 58, and the region 59 will be described. These regions are regions where two image elements (images) overlap and are subjected to alpha blend processing. Therefore, the attribute for each pixel in these areas is set by processing (see FIG. 5 or FIG. 6) for setting the attribute in the rendering processing unit 14 (see FIG. 1).

  A region 57 is a region where the image elements of the image A and the image C overlap. In this image area, the image A is the destination and the image C is the source. Accordingly, in step 103 (see FIG. 4), the rendering processing unit 14 (see FIG. 1) reads the pixel value and alpha value for each pixel included in the image information of the image C. If it is determined in step 104 (see FIG. 4) that the command is an alpha blend drawing command, in step 105 (see FIG. 4), the rendering processing unit 14 determines the pixel for each pixel included in the image information of the image A. Read value and alpha value.

Here, a specific method for calculating the value relating to the density of each source pixel in the region where the ground and the background overlap and the value relating to the density of the destination in the pixel will be described.
First, raster image information of each value is created using the pixel value and alpha value read in step 103, and a value related to the density of each source pixel in a region where the ground and the ground overlap each other is obtained. Here, in the region to be alpha-blended, the source pixel value is S, and the source alpha value is Sα (0 ≦ Sα ≦ 1). Then, a value Ks related to the processed density is generated by the calculation represented by the following expression (3).
Ks = Sα × Dk (S) (3)
Therefore, since the source is the image C in the example of FIG. 7, the value relating to the density for each pixel is αc × Dk (Dc) with reference to FIG.

Next, raster image information of each value is created using the source alpha value, the pixel value read in step 105, and the alpha value, and each destination pixel in the area where the ground and the ground overlap. Determine the value for the concentration. Here, in the area to be alpha blended, the destination pixel value is D, the source alpha value is Sα (0 ≦ Sα ≦ 1), and the destination alpha value is Dα (0 ≦ Dα ≦ 1). Then, a value Kd related to the processed density is generated by the calculation represented by the following equation (4).
Kd = (1-Sα) × Dα × Dk (D) (4)
Therefore, since the destination is the image A in the example of FIG. 7, the value relating to the density for each pixel is (1−αc) × αa × Dk (Da) with reference to FIG.

  If it is determined in step 203 (see FIG. 5) that the value related to the density of the source of a certain pixel is larger than the value related to the density of the destination, the attribute of the pixel in step 204 (see FIG. 5) is “Character” which is an attribute of the source (image C) is set. If it is determined in step 203 that the value related to the source density of a pixel is smaller than the value related to the destination density, the attribute of the pixel is set to the destination (image A) in step 205 (see FIG. 5). ) Attribute “photo”.

The area 58 is an area where the image elements of the image A and the image B overlap. In this image area, image A is the destination and image B is the source. When calculation is performed in the same manner as in the case of the region 57, the value relating to the density of each pixel of the source image B is αb × Dk (Db). A value related to the density of each pixel of the destination image A is (1−αb) × αa × Dk (Da).
If it is determined in step 203 (see FIG. 5) that the value related to the density of the source of a certain pixel is larger than the value related to the density of the destination, the attribute of the pixel in step 204 (see FIG. 5) is “Graphic” which is an attribute of the source (image B) is set. If it is determined in step 203 that the value related to the source density of a pixel is smaller than the value related to the destination density, the attribute of the pixel is set to the destination (image A) in step 205 (see FIG. 5). ) Attribute “photo”.

An area 59 is an area where the image elements of the image B and the image C overlap. In this image area, image C is the destination and image B is the source. When calculation is performed in the same manner as in the case of the region 57, the value relating to the density of each pixel of the source image B is αb × Dk (Db). A value related to the density of each pixel of the destination image C is (1−αb) × αc × Dk (Dc).
If it is determined in step 203 (see FIG. 5) that the value related to the density of the source of a certain pixel is larger than the value related to the density of the destination, the attribute of the pixel in step 204 (see FIG. 5) is “Graphic” which is an attribute of the source (image B) is set. If it is determined in step 203 that the value related to the source density of a pixel is smaller than the value related to the destination density, the attribute of the pixel is set to the destination (image C) in step 205 (see FIG. 5). ) Attribute “character”.

A region 60 is a region where the image elements of the image A, the image B, and the image C overlap. In this image area, the area 57 having the same attribute as the area where the image elements of the image A and the image C overlap is the destination, and the image B is the source. This is because the image B is overlaid last. Accordingly, the processing is performed in the same manner as in the case of the region 57. As a result, when it is determined that the value related to the source density of a certain pixel is larger than the value related to the destination density, the attribute of the pixel is the attribute of the source (image B). Is set to “Graphic”. When it is determined that the value related to the source density of a pixel is smaller than the value related to the destination density, the attribute of the pixel is set to the destination attribute (attribute of the region 57).
Here, the pixel value and the alpha value included in the image information of the region 57 are used to calculate the density-related value for each destination pixel, and these values are values processed by an alpha blending operation to be described later. .

In some cases, as in step 303 (see FIG. 6), a value related to the density of the source and the destination is corrected with a coefficient, and a correction value related to the density is calculated.
In this case, in step 302 (see FIG. 6), the rendering processing unit 14 acquires a coefficient corresponding to the attributes of the image C and the image A for the region 57. Here, since the source is the image C, the coefficient Ct (see FIG. 3C) is acquired. Since the destination is the image A, the coefficient Cp (see FIG. 3C) is acquired. And the correction value regarding the density | concentration for every pixel is calculated using the coefficient acquired in step 303 (refer FIG. 6).
Then, referring to FIG. 3, the correction value relating to the density of each source pixel is αc × Dk (Dc) × Ct. Similarly, referring to FIG. 3, the correction value related to the density of each destination pixel is (1−αc) × αa × Dk (Da) × Cp.

  If it is determined in step 304 (see FIG. 6) that the correction value related to the density of the source of a certain pixel is larger than the correction value related to the density of the destination, in step 305 (see FIG. 6), the attribute of the pixel is determined. Is set to “character” which is an attribute of the source (image C). If it is determined in step 304 that the correction value related to the source density of a pixel is smaller than the correction value related to the destination density, the attribute of the pixel is set to the destination (step 205 (see FIG. 5)). “Picture” which is an attribute of the image A) is set.

In step 302 (see FIG. 6), the rendering processing unit 14 acquires coefficients corresponding to the attributes of the image B and the image A for the region 58. Here, since the source is the image B, the coefficient Cg (see FIG. 3C) is acquired. Since the destination is the image A, the coefficient Cp (see FIG. 3C) is acquired. And the correction value regarding the density | concentration for every pixel is calculated using the coefficient acquired in step 303 (refer FIG. 6).
Then, referring to FIG. 3, the correction value relating to the density for each source pixel is αb × Dk (Db) × Cg. Similarly, referring to FIG. 3, the correction value related to the density of each destination pixel is (1−αb) × αa × Dk (Da) × Cp.

  If it is determined in step 304 (see FIG. 6) that the correction value related to the density of the source of a pixel is larger than the correction value related to the density of the destination, the attribute of the pixel is determined in step 305 (see FIG. 6). Is set to “graphic” which is an attribute of the source (image B). If it is determined in step 304 that the correction value related to the density of the source of a certain pixel is smaller than the correction value related to the density of the destination, in step 306 (see FIG. 6), the attribute of the pixel is the destination ( “Picture” which is an attribute of the image A) is set.

Further, in step 302 (see FIG. 6), the rendering processing unit 14 acquires coefficients corresponding to the attributes of the image B and the image C for the region 59. Here, since the source is the image B, the coefficient Cg (see FIG. 3C) is acquired. Since the destination is the image C, the coefficient Ct (see FIG. 3C) is acquired. And the correction value regarding the density | concentration for every pixel is calculated using the coefficient acquired in step 303 (refer FIG. 6).
Then, referring to FIG. 3, the correction value relating to the density for each source pixel is αb × Dk (Db) × Cg. Similarly, referring to FIG. 3, the correction value relating to the density of each destination pixel is (1−αb) × αc × Dk (Dc) × Ct.

  If it is determined in step 304 (see FIG. 6) that the correction value related to the density of the source of a pixel is larger than the correction value related to the density of the destination, the attribute of the pixel is determined in step 305 (see FIG. 6). Is set to “graphic” which is an attribute of the source (image B). If it is determined in step 304 that the correction value related to the density of the source of a certain pixel is smaller than the correction value related to the density of the destination, in step 306 (see FIG. 6), the attribute of the pixel is the destination ( “Character” which is an attribute of the image C) is set.

Furthermore, in the case of the region 60, the region 57 having the same attribute as the region where the image elements of the image A and the image C overlap is the destination, and the image B is the source. Accordingly, the processing is performed in the same manner as in the case of the region 57. As a result, when it is determined that the correction value related to the density of the source of a certain pixel is larger than the correction value related to the density of the destination, the attribute of the pixel is the source (image B). Is set to “graphic”. When it is determined that the correction value related to the density of the source of a certain pixel is smaller than the correction value related to the density of the destination, the attribute of the pixel is set to the attribute of the destination (attribute of the region 57).
Here, the pixel value and the alpha value included in the image information of the region 57 are used for calculating the correction value regarding the density for each pixel of the destination, and these values are values processed by the following alpha blend operation. is there.

(Specific contents of alpha blend calculation)
Next, an alpha blend process performed on pixel values and alpha values included in image information of an object (source and destination) to be combined will be described.
Here, in the region to be alpha-blended, for each color component for each RGB, the source pixel value is S, the destination pixel value is D, and the source alpha value is Sα (0 ≦ Sα ≦ 1). Then, a pixel value D ′ subjected to alpha blending processing for each RGB is generated by the alpha blending operation represented by the following expression (5).
D ′ = S × Sα + D × (1−Sα) (5)
The alpha value of the destination is Dα (0 ≦ Dα ≦ 1). Then, an alpha value D′ α subjected to alpha blending is generated by an alpha blending operation represented by the following expression (6).
D′ α = Sα + Dα × (1−Sα) (6)

FIG. 8 is a circuit diagram showing an example of an alpha blend operation circuit formed in the rendering processing unit 14.
The alpha blend operation circuit shown in FIG. 8A is a circuit for performing alpha blend processing on pixel values. This circuit includes a multiplier 141, a computing unit 142 that performs computation of (1−Sα), a multiplier 143, and an adder 144. The multiplier 141 multiplies the source pixel value (S) by the source alpha value (Sα) to obtain S × Sα. The multiplier 143 multiplies the destination pixel value (D) by (1-Sα) obtained by the computing unit 142 to obtain D × (1-Sα). The adder 144 adds the multiplication result of the multiplier 141 and the multiplication result of the multiplier 143 to obtain D ′ = S × Sα + D × (1−Sα).

  The alpha blend operation circuit shown in FIG. 8B is a circuit for performing alpha blend processing on the alpha value. This circuit includes an arithmetic unit 145, a multiplier 146, and an adder 147 that perform an operation of (1-Sα). The multiplier 146 multiplies the destination alpha value (Dα) by (1-Sα) obtained by the calculator 145 to obtain Dα × (1-Sα). Then, the adder 147 adds the source alpha value (Sα) and the multiplication result of the multiplier 146 to obtain D′ α = Sα + Dα × (1−Sα).

The flow of processing for creating an image of an area where image elements overlap by the alpha blend processing has been described above. However, these are only examples.
In the above embodiment, the attribute in the region where the ground and the ground overlap each other is determined by comparing the value related to the density of the source and the destination (or the correction value related to the density), but the present invention is not limited to this. For example, the CIE 1976 (L * a * b *) space or the CIE 1976 (L *) using a predetermined color conversion formula generally known based on the pixel values included in the image information (see FIG. 3A). Find the L value in u * v *) space. Then, by comparing the L value of the source and the destination for each pixel, the attribute in the region where the ground and the ground overlap each other may be determined. In this case, in order to reduce the image quality degradation due to attribute switching and obtain a higher quality output image, the pixel attribute in the area where the ground and the background overlap is changed to the attribute of the image with high density and inconspicuousness. It will be set.

  In FIG. 3C, the coefficient is set for each image element. However, as shown in FIG. 3D, the coefficient may be further divided into a source image coefficient and a destination coefficient. In this way, pixel attribute determination can be controlled in more detail from the above embodiment, and image quality deterioration due to attribute switching can be reduced.

  In FIG. 3C, the coefficients are stored in the secondary storage unit 20 (see FIG. 1), but the present invention is not limited to this. For example, the coefficient may be included in the image information. In this case, for example, the PDL analysis unit 13 reads out the coefficient stored in the secondary storage unit 20 (see FIG. 1) and adds it to the image information. In step 302 (see FIG. 6), the rendering processing unit 14 acquires a coefficient from the source image information. The image processing apparatus (image processing unit 10) (see FIG. 1) may include a coefficient setting unit that sets a coefficient for each attribute. Further, the printer driver held in the PC 3 (see FIG. 1) may have a function for setting this coefficient.

Furthermore, the arithmetic circuit that performs the alpha blending operation is not limited to that shown in FIG. 8, and any arithmetic circuit that can obtain the equations (5) and (6) as a result of the operation may be used.
In the present specification, a specific form for providing the program is not described. However, for example, the program may be provided by a bidirectional communication means such as the Internet, or may be recorded on a CD-ROM or the like. The embodiment may be provided by being held in a medium.

1 is a block diagram illustrating an example of a configuration of an image forming apparatus including an image processing apparatus of the present invention. It is a block diagram which shows the internal structure of an image process part. It is a figure which shows the example of the image information of the image used as the object of a synthetic | combination process, and the example of the coefficient linked | related for every attribute. It is a flowchart which shows an example of the procedure of the rendering process in a rendering process part. It is a flowchart which shows an example of the procedure of the process which sets the attribute of the area | region where a several image element overlaps for every pixel. It is a flowchart which shows the other example of the procedure of the process which sets the attribute of the area | region where a several image element overlaps for every pixel. It is the figure which showed an example of the attribute set to the area | region by which the alpha blend process was carried out. It is the circuit diagram which showed an example of the alpha blend operation circuit formed in the rendering process part.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus, 3 ... Personal computer (PC), 4 ... Image reading apparatus, 10 ... Image processing part (image forming apparatus), 11 ... Reception part, 12 ... Input buffer, 13 ... PDL analysis part, 14 ... Rendering Processing unit 15 ... Intermediate buffer 16 ... Color conversion processing unit 17 ... Screen processing unit 20 ... Secondary storage unit 30 ... Control unit 40 ... Image forming unit 101 ... CPU 104 Non-volatile memory 105 ... Interface part

Claims (9)

In an image processing apparatus that performs processing for combining images based on the transparency of each of the plurality of image elements in a region where a plurality of image elements overlap,
For each of the plurality of image elements, the transparency, and accepting means for accepting image information including information pixel values, and to attribute,
Storage means for storing coefficients individually set for the attributes included in the image information;
Information on the attribute included in the image information by calculating a value related to the density in the region based on the transparency included in the image information and the information on the pixel value included in the image information regarding the region where the plurality of image elements overlap. Calculation means for correcting a value related to the density in the area by the coefficient read from the storage means based on
Setting means for comparing values of the density calculated and corrected by the calculation means for each of the plurality of image elements, and setting an attribute of an image element having a large value of the density as an attribute of the image element of the region. An image processing apparatus. The storage means, for the attribute included in the image information of each image element, a coefficient when the image element is combined and becomes a ground, and a coefficient when the image element is combined and becomes a background, respectively. The image processing apparatus according to claim 1, wherein the image processing apparatus is stored. The setting means compares the value relating to the density for each pixel of the region, sets the attribute of the image element determined to be large as the attribute of the image element for each pixel,
The image processing apparatus according to claim 1, wherein image processing corresponding to an attribute of an image element set by the setting unit is performed for each pixel. In an image forming apparatus that forms an image by performing a process of synthesizing an image based on the transparency of each of the plurality of image elements in a region where the plurality of image elements overlap.
For each of the plurality of image elements, the transparency, and accepting means for accepting image information including information pixel values, and to attribute,
Storage means for storing coefficients individually set for the attributes included in the image information;
Image processing means for performing composition processing of the image information received by the receiving means;
Image forming means for forming the plurality of image elements synthesized on a recording medium based on the image information synthesized by the image processing means,
The image processing means includes
Information on the attribute included in the image information by calculating a value related to the density in the region based on the transparency included in the image information and the information on the pixel value included in the image information regarding the region where the plurality of image elements overlap. A calculation unit for correcting a value related to the density in the region by the coefficient read from the storage unit based on
A setting unit configured to compare the value related to the density calculated and corrected by the calculation unit for each of the plurality of image elements, and to set an attribute of an image element having a large value related to the density as an attribute of the image element of the region. An image forming apparatus. The storage means, for the attribute included in the image information of each image element, a coefficient when the image element is combined and becomes a ground, and a coefficient when the image element is combined and becomes a background, respectively. 5. The image forming apparatus according to claim 4, wherein the image forming apparatus stores the image.   The image processing means compares the value related to the density for each pixel of the region, and sets the attribute of the image element determined to be large as the attribute of the image element for each pixel. The image forming apparatus according to claim 4, wherein image processing corresponding to the attribute of the image element set by the setting unit is performed for each pixel. In a program for realizing a function of synthesizing an image based on the transparency of each of the plurality of image elements in a region where the plurality of image elements overlap,
On the computer,
For each of the plurality of image elements, the transparency, the acquisition function of acquiring image information including information pixel values, and to attribute,
Information on the attribute included in the image information by calculating a value related to the density in the region based on the transparency included in the image information and the information on the pixel value included in the image information regarding the region where the plurality of image elements overlap. A coefficient based on the image data is read from a storage unit storing coefficients set individually for the attributes of each image element, and a calculation function for correcting a value related to the density in the region by the coefficient ;
A setting function for comparing values of the density calculated and corrected by the calculation function for each of the plurality of image elements, and setting an attribute of an image element having a large value of the density as an attribute of the image element of the region; Program to let you. The calculation function includes a coefficient based on information about the attribute included in the image information, a coefficient when the image element is combined with the attribute of each image element to become the ground, and a base when the image element is combined 8. The program according to claim 7, wherein a coefficient at the time of reading is read from storage means storing each, and the value relating to the density in the region is corrected by the coefficient. The setting function compares the value related to the density for each pixel in the region, sets the attribute of the image element determined to be large as the attribute of the image element for each pixel,
8. The program according to claim 7, wherein image processing corresponding to the attribute of an image element set by the setting function is performed for each pixel.

Images