JP4306841B2 - Image processing apparatus and method, and computer-readable memory - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image processing apparatus and method for processing and outputting input image data, and a computer-readable memory.
[0002]
[Prior art]
Conventionally, an image processing system as shown in FIG. 12 is known.
[0003]
This is an image processing system that uses a host computer 101 to create a page layout document such as DTP, a word processor, a graphic document, and the like, and outputs a hard copy by a laser beam printer, an inkjet printer, or the like.
[0004]
Reference numeral 102 denotes an application that runs on the host computer 101. Typical examples include word processor software such as Microsoft Word (Microsoft Word: registered trademark) of Microsoft Corporation and page maker (PageMaker: registered trademark) of Adobe Corporation. Page layout software is famous. Digital document data created by these software is transmitted to the printer driver 103 via an operating system (OS) (not shown).
[0005]
Digital document data is usually represented as a set of command data representing figures, characters, etc. constituting one page, and these command data are transmitted to the printer driver 103. A series of commands is expressed as a language system called PDL (page description language), and typical examples of PDL are GDI (registered trademark) and Postscript (registered trademark).
[0006]
The printer driver 103 transfers the transmitted PDL command to the rasterizer 105 in the raster image processor 104. The rasterizer 105 develops characters, graphics, and the like expressed by the PDL command into a two-dimensional bitmap image for actual printer output. A bitmap image is referred to in this way because it is an image configured by repeating a two-dimensional plane as a one-dimensional raster (line). The developed bitmap image is temporarily stored in the image memory 106. The bitmap image stored in the image memory 106 is transmitted to the color printer 108, and an image based on the bitmap image is formed on the recording medium by the image forming unit 108.
[0007]
FIG. 11 schematically shows the operation executed by the above configuration. A document image 111 displayed on the host computer 101 is transmitted as a PDL command string 112 to the rasterizer 105 via the printer driver 103. Next, the rasterizer 105 expands the two-dimensional bitmap image 113 on the image memory 106.
[0008]
The developed bitmap image 113 is transmitted to the color printer 107. The color printer 107 is equipped with a known electrophotographic system or ink jet recording system image forming unit 108. Using this image forming unit 108, a visible image is formed on a recording medium and printed out. Note that the bitmap image 113 in the image memory 107 is transferred in synchronization with a synchronization signal, a clock signal, or a transfer request for a specific color component signal necessary for operating the image forming unit 108.
[0009]
[Problems to be solved by the invention]
However, in the conventional image processing system, it is clear that various problems arise when considering an image forming unit used for outputting a bitmap image.
[0010]
For example, normally, a color printer uses a four-color toner or ink of cyan (C), magenta (M), yellow (Y), and black (K) to form a color image on a print output. Colors in image formation are expressed based on the principle of so-called subtractive color mixing.
[0011]
On the other hand, when an application of a host computer displays an image, a color monitor is usually used. The color monitor uses three additive primary colors of red (R), green (G), and blue (B). Express color.
[0012]
Accordingly, the colors of characters and figures constituting the document, or the color of the image obtained by laying out a photograph or the like read by a scanner are all expressed as a color in which R, G, and B are mixed at a certain ratio.
[0013]
That is, the rasterizer 105 converts the color information defined by R, G, and B as PDL and transferred from the host computer 101 into C, M, Y, and K, then generates a bitmap image and transmits it to the printer. There is a need.
[0014]
However, the method for converting RGB signals into CMYK signals is not uniquely determined, and the optimum conversion method differs depending on the graphic attributes defined in PDL. For example, referring to the example of FIG. 13, the image 114 is a natural image read by a scanner or the like, the image 115 is an electronically generated graphic image such as a circle or a rectangle, and the image 116 is a different attribute such as a character (TEXT) image. have. Here, when the color of the image 116 is defined as black with R = G = B = 0, the optimum CMYK signal for this is expressed as C = M = Y = 0 and K = K. = 255. That is, it is preferable to reproduce black characters using only black toner among the four colors of toner of the printer. On the other hand, when the pixel value of the specific pixel of the natural image of the image 114 is R = G = B = 0, if it is converted into C = M = Y = 0 and K = 255 like the image 116, Originally, what should express the highest density portion in a natural image is reproduced with only black toner, so that the absolute density is insufficient. Therefore, in this case, it is preferable that the absolute density is increased by converting into values such as C = M = Y = 100 and K = 255.
[0015]
In order to solve such a problem, the rasterizer 105 develops a bitmap image using the RGB signal values without performing conversion to the CMYK signal, and the bits of the RGB signal transmitted on the image forming unit 108 side. A character image area is detected from a map image using a known image area separation process, and a conversion method from RGB signals to CMYK signals is switched between the detected character image area and other areas to generate a CMYK signal. It is also considered to output the output.
[0016]
However, in this case, it is not always possible to detect 100% of the character image area by the image area separation process, and it may be erroneously detected as a character area in the natural image area, so that it is not reliable. There is a bug.
[0017]
As another example, a case where the image forming unit 108 can reproduce only binary dots can be considered. In this case, the rasterizer 105 develops a multivalued bitmap image of the CMYK signal in the image memory 106, and the image forming unit 108 that has received the image performs a known binarization process such as an error diffusion method or a dither process. After the value image signal is converted into a binary image signal, it is printed out.
[0018]
At this time, the optimum binarization method also changes depending on the attribute of the image. That is, for graphics such as characters and figures, it is preferable to binarize the image by reducing the size of the dither matrix used for the dither processing, and for natural images such as photographs, the size of the dither matrix is increased. It is preferable to emphasize tone reproducibility.
[0019]
In this case as well, a method of adaptively switching the dither matrix size by performing image area separation processing on the multi-valued bitmap image transferred from the image memory 106 is considered. It cannot be prevented.
[0020]
The present invention has been made in view of the above problems, and provides an image processing apparatus and method, and a computer-readable memory capable of outputting a high-quality image in which images of a plurality of types of attributes are mixed. Objective.
[0021]
[Means for Solving the Problems]
In order to achieve the above object, an image processing apparatus according to the present invention comprises the following arrangement. That is,
An image processing apparatus that processes and outputs input image data,
Input means for inputting image data composed of a plurality of objects;
Expansion means for expanding the object into bitmap image data;
Generating means for generating attribute map information including at least an edge boundary flag indicating the configuration of the bitmap image data based on the bitmap image data expanded by the expansion means and the attribute of the object;
Image processing means for performing a plurality of image processing on the bitmap image data expanded by the expansion means based on the attribute map information generated by the generation means,
Said generating means, if the smoothing process is included in the plurality of image processing, the edge boundary flag, generated outside the region of the edge of an object, smoothing processing by not generated inside the region of the edge Controls whether to enable or not .
[0022]
Preferably, the method for generating attribute map information is changed for an area where a bitmap image with a specific attribute has already been developed.
Preferably, the attribute map information is generated in association with a two-dimensional coordinate position of the bitmap image data, and the bitmap image data and the attribute map information having the same coordinates as the bitmap image data are synchronized. And transferred to the image forming unit.
[0025]
Preferably, the attribute map information includes at least a vector flag, a character flag, an edge flag, and an edge boundary flag.
[0026]
Also, preferably, the plurality of image processing comprises at least dithering.
[0027]
In order to achieve the above object, an image processing method according to the present invention comprises the following arrangement. That is,
An image processing method for processing and outputting input image data,
An input process for inputting image data composed of a plurality of objects;
A development step of developing the object into bitmap image data;
A generation step of generating attribute map information including at least an edge boundary flag indicating the configuration of the bitmap image data based on the bitmap image data expanded in the expansion step and the attribute of the object;
An image processing step of performing a plurality of image processing on the bitmap image data expanded in the expansion step based on the attribute map information generated in the generation step;
Said generating step, when the smoothing process is included in the plurality of image processing, the edge boundary flag, generated outside the region of the edge of an object, smoothing processing by not generated inside the region of the edge Controls whether to enable or not .
[0028]
In order to achieve the above object, a computer readable memory according to the present invention comprises the following arrangement. That is,
A computer-readable memory storing a program for causing a computer to execute image processing for processing and outputting input image data,
An input process for inputting image data composed of a plurality of objects;
A development step of developing the object into bitmap image data;
A generation step of generating attribute map information including at least an edge boundary flag indicating the configuration of the bitmap image data based on the bitmap image data expanded in the expansion step and the attribute of the object;
Based on the attribute map information generated in the generation step, an image processing step of performing a plurality of image processing on the bitmap image data expanded in the expansion step;
Program for executing a computer is stored,
Said generating step, when the smoothing process is included in the plurality of image processing, the edge boundary flag, generated outside the region of the edge of an object, smoothing processing by not generated inside the region of the edge Controls whether to enable or not .
[0029]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.
[0030]
FIG. 1 is a block diagram showing a configuration of an image processing system according to an embodiment of the present invention.
In the figure, reference numerals 10 to 15 are the same as reference numerals 101 to 106 in FIG. 12, and reference numerals 18 and 19 are the same as reference numerals 107 and 108 in FIG.
[0031]
The feature of the present invention is the attribute map memory 16 and the image processing unit 17. Here, the image processing unit 17 is shown to exist independently, but the image processing unit 17 may be included in the raster image processor 13 or the color printer 18.
[0032]
The rasterizer 14 generates a bitmap image on the image memory 15 on the basis of commands associated with individual parts (hereinafter referred to as objects) constituting the image. At this time, the attribute of the object and the generated bitmap are generated. Based on the image, attribute map information is generated by a method described later and written to the attribute map memory 16.
[0033]
That is, the rasterizer 14 generates attribute map information based on the attribute of the command representing the object and the bitmap image data generated for writing to the image memory 15. At this time, it is naturally possible to refer to the contents of the already developed image memory 15 as bitmap image data.
[0034]
The image processing unit 17 performs various image processing on the bitmap image data in the image memory 15 and outputs the data to the color printer 18. At this time, the image processing method is appropriately switched with reference to the attribute map information in the attribute map memory 16.
[0035]
First, a method for generating attribute map information will be described in detail.
[0036]
When the bitmap image data developed in the image memory 15 is as shown in FIG. 2, enlarged views of the area (a) and the area (b) are shown in FIGS. 3 and 4, respectively.
[0037]
FIG. 3 shows a case where a bitmap image of a circle is generated based on a command for drawing a circular object. Reference numeral 21a represents bitmap image data written to the image memory 15, and pixel values in units of minute pixels are arranged in a two-dimensional array, for example, as 8-bit integer values.
[0038]
Reference numerals 22 a to 25 a indicate bit map image data, attribute map information divided for each attribute, and attribute information flags thereof. The attribute map information is written in the attribute map memory 16. Attribute information flags (in this embodiment, four types of vector flag, character flag, edge flag, and edge boundary flag) are each the same pixel as the bitmap image data in the image memory 15 by 1 bit (0 or 1). Generated in an array. In FIG. 3, 0 is expressed as a white rectangle and 1 is expressed as a black rectangle.
[0039]
The vector flag is a flag that is 1 in a vector image area such as a character or graphic, and 0 in other background parts or continuous tone photograph parts (area (c) in FIG. 2). Accordingly, in this case, the data 22a which is the entire inside of the circular object has 1 as a vector flag. The data 22a can usually be generated based on a command for drawing a circular object. In the present invention, since the contents of the bitmap image 21a are referred to, the newly painted area is detected in the bitmap image 21a, and the data 22a is obtained with 1 as the whole area as a vector flag. Can be.
[0040]
The character flag is a flag which is 1 in the character image area and 0 in other cases. Therefore, in this case, since the circular object is not a character, the data 23a is all zero.
[0041]
The edge flag is a flag that is 1 at the boundary portion of the object and 0 at other times. Therefore, in this case, the data 24a that is the boundary of the circular object has 1 as an edge flag. This can be generated by detecting a pixel that changes from 0 to 1 in the data 22a and setting 1 to the detected pixel position.
[0042]
The edge boundary flag is a flag that becomes 1 at a pixel adjacent to the edge flag. In this case, by detecting pixels adjacent to four neighborhoods of the pixel that becomes 1 in the data 24a, 1 is set as the edge boundary flag in the data 25a that is located both inside and outside the data 24a that is the edge. However, depending on the contents of image processing to be described later, it may be better to set only the pixels outside the edge as the edge boundary flag. In this case, referring to the original image memory 21a simultaneously with the data 24a, it is possible to prevent the edge boundary flag from being generated in the halftone portion (region shown in gray) inside the circle.
[0043]
FIG. 4 is an example in which attribute map information is similarly generated for a character object. The meanings of 21b to 25b are the same as those of 21a to 25a and the generated attribute map information is almost the same, but only the data 23b is different from the data 23a, and 1 is set as the character flag. This is because the character flag is set to 1 throughout the character because 21b is a character object.
[0044]
The attribute map information is generated by the above procedure. Then, the generated bitmap image data and attribute map information are transferred to the image processing unit 17 together with the synchronization signal. At this time, the data of the predetermined pixel position in the image memory 15 and the attribute map information of the corresponding pixel must be transferred in association with each other. That is, when the pixel value of a specific pixel in the image memory 15 is transmitted to the image processing unit 17, the attribute map information (flag) of the same pixel must be transmitted almost simultaneously. Note that in the continuous tone image area shown in the area (c) of FIG. 2 and the background area where the image is not drawn, all the flags are 0 as apparent from the above description.
[0045]
The image processing unit 17 performs various image processing on the pixel values from the image memory 15, and the processing method is controlled by a flag from the attribute map memory 16.
[0046]
That is, the bitmap image data developed in the image memory 15 is switched according to the attribute map information, for example, dither matrix size switching, spatial filter processing such as edge enhancement, or so-called SST. Performs switching of smoothing processing.
[0047]
Here, a processing example in the case of switching the dither matrix size according to the attribute map information will be described with reference to FIGS.
[0048]
5-7 is a figure which shows an example of the dither matrix of embodiment of this invention. The bitmap image data used in this embodiment is an 8-bit integer value (0 to 255) for each pixel. Then, the ON / OFF of the output pixel is controlled by binarizing the value in each cell of the dither matrix as a threshold value. FIG. 5 shows a 3 × 3 dither matrix. If one pixel is 600 dpi, 10 gradations can be expressed with a resolution of 200 dpi. FIG. 6 shows a 5 × 5 size and can express 120 dpi / 26 gradations. Since FIG. 7 is an 8 × 8 size, 75 dpi / 65 gradations are obtained.
[0049]
Therefore, the attribute map information corresponding to the target pixel is referred to, and when the continuous tone region, that is, the vector flag is 0, binarization is performed with the dither matrix of FIG. If the graphic area, that is, the vector flag is 1 and the character flag is 0, binarization is performed using the dither matrix shown in FIG. When the character image area, that is, the character flag is 1, binarization is performed using the dither matrix shown in FIG. As a result, bitmap images of multiple types of attribute map information are mixed, such that photographs can be reproduced with high resolution while reproducing gradation with emphasis on gradation, and graphics can be reproduced between them. However, a high-quality output image can be obtained.
[0050]
Further, in the case of a pixel whose edge flag is 1 by referring to the edge flag prior to the dither processing, the sharpness of characters and graphics can be obtained by spatially convolving an edge enhancement filter as shown in FIG. Can be further improved.
[0051]
It is also possible to perform smoothing processing in which halftone pixels are added to the edge portions of characters and graphics to reduce edge portion jaggies. In this process, for example, halftone pixels are added to the outside of the edge portion of the image in FIG. A more effective result can be obtained by performing this process only for pixels having an edge boundary flag of 1.
[0052]
Here, in FIG. 10, only the pixels outside the edge boundary are processed, but this is because the inside of the figure is not white, and if the same processing is performed on the inner edge boundary, a problem occurs. is there. Therefore, the edge boundary flag is controlled according to the contents of the object so that the edge boundary flag becomes 1 only outside the edge, or the edge boundary flag is set to 0 when the background is not white.
[0053]
In the above embodiment, as the attribute map information of an image, four types of attributes, which are a vector image, a character image, an edge, and an edge boundary, have been described. It is not limited. For example, various flags such as whether the object is a chromatic color or an achromatic color, an edge portion on the background or an edge portion on a white background, or an edge portion in a photograph can be applied.
[0054]
Further, the switching of the image processing method based on the attribute map information is not limited to the above embodiment. In addition, the color conversion method is switched from the RGB signal to the YMCK signal, the bitmap image data is compressed, and the printer Various methods such as switching of the compression method when transferring to the unit are conceivable.
[0055]
Also, since the bitmap image data that has already been developed is referred to when the flag is generated, for example, when a character is overwritten on an area where a gradation image has already been developed, a character flag is set. It is also possible to prevent such a situation.
[0056]
Finally, the processing flow of the processing executed in this embodiment will be described with reference to FIG.
[0057]
FIG. 11 is a flowchart showing a processing flow of processing executed in the embodiment of the present invention.
[0058]
First, in step S101, each object of image data composed of a plurality of input objects is developed into bitmap image data by the rasterizer 14. The developed bitmap image data is stored in the image memory 15. In step S102, attribute map information of each bitmap image data is generated based on the developed bitmap image data and the attribute of the object. The generated attribute map information is stored in the attribute map memory 16. In step S103, based on the generated attribute map information, an image processing method for each bitmap image data is determined and executed by the image processing unit 17. Then, an image based on the image-processed bitmap image data is formed in the image forming unit 18.
[0059]
As described above, according to the present embodiment, image processing suitable for the attribute map information can be performed on a bitmap image in which bitmap images of a plurality of types of attribute map information are mixed. An output image based on the bitmap image can be output with higher quality.
[0060]
Note that the present invention can be applied to a system (for example, a copier, a facsimile machine, etc.) consisting of a single device even if it is applied to a system composed of a plurality of devices (for example, a host computer, interface device, reader, printer, etc.) You may apply.
[0061]
Another object of the present invention is to supply a storage medium storing software program codes for implementing the functions of the above-described embodiments to a system or apparatus, and the computer (or CPU or MPU) of the system or apparatus stores the storage medium. Needless to say, this can also be achieved by reading and executing the program code stored in the.
[0062]
In this case, the program code itself read from the storage medium realizes the functions of the above-described embodiments, and the storage medium storing the program code constitutes the present invention.
[0063]
As a storage medium for supplying the program code, for example, a floppy disk, a hard disk, an optical disk, a magneto-optical disk, a CD-ROM, a CD-R, a magnetic tape, a nonvolatile memory card, a ROM, or the like can be used.
[0064]
Further, by executing the program code read by the computer, not only the functions of the above-described embodiments are realized, but also an OS (operating system) operating on the computer based on the instruction of the program code. It goes without saying that a case where the function of the above-described embodiment is realized by performing part or all of the actual processing and the processing is included.
[0065]
Further, after the program code read from the storage medium is written into a memory provided in a function expansion board inserted into the computer or a function expansion unit connected to the computer, the function expansion is performed based on the instruction of the program code. It goes without saying that the CPU or the like provided in the board or the function expansion unit performs part or all of the actual processing, and the functions of the above-described embodiments are realized by the processing.
[0066]
【The invention's effect】
As described above, according to the present invention, it is possible to provide an image processing apparatus and method, and a computer-readable memory capable of outputting a high-quality image in which images of a plurality of types of attributes are mixed.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of an image processing system according to an embodiment of the present invention.
FIG. 2 is a diagram illustrating an example of a processing target bitmap image according to the embodiment of the present invention.
FIG. 3 is a diagram illustrating attribute map information according to the embodiment of this invention.
FIG. 4 is a diagram for describing attribute map information according to the embodiment of this invention.
FIG. 5 is a diagram illustrating an example of a dither matrix according to an embodiment of the present invention.
FIG. 6 is a diagram illustrating an example of a dither matrix according to the embodiment of the present invention.
FIG. 7 is a diagram showing an example of a dither matrix according to the embodiment of the present invention.
FIG. 8 is a diagram illustrating an example of an edge enhancement filter according to the embodiment of this invention.
FIG. 9 is a diagram for explaining smoothing processing according to the embodiment of the present invention.
FIG. 10 is a diagram for explaining smoothing processing according to the embodiment of the present invention.
FIG. 11 is a flowchart showing a processing flow of processing executed in the embodiment of the present invention.
FIG. 12 is a block diagram illustrating a configuration of a conventional image processing system.
FIG. 13 is a diagram for explaining a processing procedure executed in a conventional image processing system.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Host computer 11 Application 12 Printer driver 13 Raster image processor 14 Rasterizer 15 Image memory 16 Attribute map memory 17 Image processor 18 Color printer 19 Image forming unit

Claims (11)

An image processing apparatus that processes and outputs input image data,
Input means for inputting image data composed of a plurality of objects;
Expansion means for expanding the object into bitmap image data;
Generation means for generating attribute map information including at least an edge boundary flag indicating the configuration of the bitmap image data based on the bitmap image data expanded by the expansion means and the attribute of the object;
Image processing means for performing a plurality of image processing on the bitmap image data expanded by the expansion means based on the attribute map information generated by the generation means,
Said generating means, if the smoothing process is included in the plurality of image processing, the edge boundary flag, generated outside the region of the edge of an object, smoothing processing by not generated inside the region of the edge An image processing device that controls whether to enable or not . The image processing apparatus according to claim 1, wherein a method for generating attribute map information is changed for an area in which a bitmap image having a specific attribute has already been developed. The attribute map information is generated in association with the two-dimensional coordinate position of the bitmap image data, and the bitmap image data and the attribute map information having the same coordinates as the bitmap image data are synchronized with the image forming unit. The image processing apparatus according to claim 1, wherein the image processing apparatus is transferred to the image processing apparatus. The image processing apparatus according to claim 1, wherein the attribute map information includes at least a vector flag, a character flag, an edge flag, and the edge boundary flag. The image processing apparatus according to claim 1, wherein the plurality of image processes include at least a dither process. An image processing method for processing and outputting input image data,
An input process for inputting image data composed of a plurality of objects;
A development step of developing the object into bitmap image data;
A generation step of generating attribute map information including at least an edge boundary flag indicating the configuration of the bitmap image data based on the bitmap image data expanded in the expansion step and the attribute of the object;
An image processing step of performing a plurality of image processing on the bitmap image data expanded in the expansion step based on the attribute map information generated in the generation step;
Said generating step, when the smoothing process is included in the plurality of image processing, the edge boundary flag, generated outside the region of the edge of an object, smoothing processing by not generated inside the region of the edge An image processing method characterized by controlling whether to enable or not . The image processing method according to claim 6, wherein a method for generating attribute map information is changed for an area where a bitmap image having a specific attribute has already been developed. The attribute map information is generated in association with the two-dimensional coordinate position of the bitmap image data, and the bitmap image data and the attribute map information having the same coordinates as the bitmap image data are synchronized with the image forming unit. The image processing method according to claim 6, further comprising: The image processing method according to claim 6, wherein the attribute map information includes at least a vector flag, a character flag, an edge flag, and an edge boundary flag. The image processing method according to claim 6, wherein the plurality of image processes include at least a dither process. A computer-readable memory storing a program for causing a computer to execute image processing for processing and outputting input image data,
An input process for inputting image data composed of a plurality of objects;
A development step of developing the object into bitmap image data;
A generation step of generating attribute map information including at least an edge boundary flag indicating the configuration of the bitmap image data based on the bitmap image data expanded in the expansion step and the attribute of the object;
Based on the attribute map information generated in the generation step, an image processing step of performing a plurality of image processing on the bitmap image data expanded in the expansion step;
Program for executing a computer is stored,
Said generating step, when the smoothing process is included in the plurality of image processing, the edge boundary flag, generated outside the region of the edge of an object, smoothing processing by not generated inside the region of the edge A computer-readable memory for controlling whether to enable or not .

Images