The present document incorporates by reference the entire contents of Japanese priority document, 2002-359424 filed in Japan on Dec. 11, 2002.
1) Field of the Invention
The present invention relates to a technology for image processing, and more particularly a method of, an apparatus for, and a computer program for an image processing in a digital color copier, a color printer, a color facsimile machine, and the like.
2) Description of the Related Art
A technology known as the image area separation is currently in use for image processing in digital a color copier, a color printer, a color facsimile machine, and the like. The image area separation is a process in which pixel areas of an image being scanned are recognized as a character area or an intermediate tone area of a picture, etc. and an image area separation data (attribute information) is created for each pixel. Appropriate processes for the character areas and the intermediate tone areas are carried out with a help of the image area separation data. For instance, based on the image area separation data, a space filtering process may be carried out to enhance a resolution of the character area, or an intermediate toning process may be carried out to enhance a contrast of the intermediate tone area.
A color image that is output from the digital color copier is obtained by superposing four color plates, K (black), C (cyan), M (magenta), and Y (yellow). In order to control a printing timing of the different color plates, the image needs to be stored once in memory. However, to avoid occupation of too much memory, a method is adopted by which image data is compressed before being storing in a memory. Recently, there has been a rising demand to not only be able to obtain an output of a scanned image output, but also to be able to store the image as a digital data, to be output whenever required, obviating a need for an original document for a subsequent copies, or to be used on a personal computer (PC), and the like. For these purposes as well, the image data needs to be compressed to an appropriate size. It has therefore become common in the image processing of the digital color copier to incorporate a step of compressing the image data and storing the data in the memory.
If scanned image data is to be transferred as a digital data to the personal computer (PC), instead of being output on a paper, any data at any stage of the processing can be transferred. However, it would be ideal if the image data that is transferred to the PC is the image data that is compressed and stored in the memory. The name of the image data thus transferred may be edited on the PC and may also be output on a paper. In order to be able to obtain an output on a paper, the edited data, which has been processed only up to the compression stage, must once again be entered in the memory so that the image quality is identical with that of a normal copier system. However, once an image that is transferred to another device and is read again loses its image area separation data (attribute information). Consequently, a process switching based on the image area is not possible, resulting in inferior image quality. Even if the image area separation data (attribute information) is created again for the image data that has been transferred to an outside device and scanned again, the separation accuracy would be low as compared to the image area separation data (attribute information) of the original image due to a fact that the image data has been compressed.
It is an object of the present invention to solve at least the problems in the conventional technology.
The apparatus for image processing according to one aspect of the present invention includes a first attribute creating unit that creates, from a first image data, a first attribute information that indicates image characteristics, a storing unit that stores the first attribute information, a processing unit that carries out different processing for different image area of the first image data based on the first attribute information, a transferring unit that transfers the first image data to outside, an input unit that inputs a second image data from the outside, and a determining unit that determines whether the first attribute of the second image data is stored in the storing unit, and specifies the first attribute information as an active attribute information upon determining that the first attribute information of the second image data is stored in the storing unit, wherein the processing unit carries out a processing of the second image data based on the active attribute information.
The method of image processing according to another aspect of the present invention includes creating, from a first image data, a first attribute information that indicates image characteristics, storing the first attribute information, performing different processing for different image area of the first image data based on the first attribute information, transferring the first image data to outside, inputting a second image data from the outside, determining unit whether the first attribute of the second image data is stored in the storing unit, specifying the first attribute information as an active attribute information upon determining that the first attribute information of the second image data is stored in the storing unit, and performing different processing for different image area of the first image data based on the active attribute information.
The computer program for image processing according to still another aspect of the present invention realizes the method according to the present invention on a computer.
The computer-readable recording medium according to still another aspect of the present invention stores a computer program for image processing according to the present invention.
The other objects, features and advantages of the present invention are specifically set forth in or will become apparent from the following detailed descriptions of the invention when read in conjunction with the accompanying drawings.
Exemplary embodiments of a method of, an apparatus for, and a computer program for image processing according to the present invention are explained in detail with reference to the accompanying drawings. However, it is to be noted that the invention is not limited by the embodiments described herein.
The scanner in
The image area separation process involves determining if each pixel area of the image data is a character area or a picture area and creating an image area separation data (attribute information) based on the result of the determination. Thus, with the help of the image area separation data, an image processing suited to each area can be carried out. The image area separation process carries out edge detection, halftone detection, etc., and if the area is a non-halftone or an edge, the area is taken to be a character area (a binary image area composed of a character or a line). If the area is not a non-halftone or an edge, the area is taken to be a picture area (an intermediate toner image area such as a picture or a halftone print).
The halftone detection may be carried out, for instance, by employing the peak pixel detection method disclosed in the article titled “Image area separating method for graphics containing characters and images (halftone, picture), Electronic Information Communication Society, vol. J75-D-II No. 1 pp. 39-47, January 1992”. In the peak pixel detection, it is determined from the concentration relation with the surrounding pixels whether the pixel of interest is a peak indicating the peak of the change in density. To be more specific, when the density level of the central pixel in a block formed from M×M pixels is higher or lower than the density level of the surrounding pixels, it is determined whether the central pixel is a peak pixel by the following method.
In other words, when the block is as shown in
When the block is as shown
In other words, when the absolute value obtained from the difference between the average value of the pixel levels of the pixels on either side of the central pixel and the density of the central pixel is greater than the threshold value ΔmTH, the central pixel is determined to be a peak. Based on the peak pixel data, it can be judged whether the peak pixel area is a halftone area or not. To explain in the simplest terms, this is done by counting the peak pixels for each block of a predetermined size and judging a block to be a halftone area if the number of peak pixels is not less than a predetermined number n.
Any other method may also be used in the halftone area detection. Also, the areas may be separated on the basis of character/halftone/picture areas or black and white character/color character/image area, etc. In the image area separation process, an image area separation method may be employed according to the method of separation of areas to be judged. Further, edge detection and halftone detection need not necessarily be a binary decision but can create multinary attribute information like the image area separation process. For instance, for edge detection, a multinary attribute information can be created by using a number of threshold values that binarize the edge value.
A scanner γ correction process converts an image signal that is read in proportion to the reflection coefficient to an image signal that is proportional to the density.
A filtering process carries out changes such as noise elimination, sharpening of characters, etc. in order to improve the image quality by smoothing or enhancing character edges. The filtering process carries out suitable processes for character areas/picture areas in accordance with the image area separation data (attribute information) created by the image area separation process. For instance, in the character area the filtering process would carry out a process that favors sharpness in order to enhance high frequency components, and in the picture area the filter process would carry out smoothing in order to emphasize contrast.
A compression process compresses the post-filtered image data. The compression method used is irreversible. For instance JPEG (Joint Photographic Experts Group) method among the existing methods may be used. Besides, compression methods using conventional technology may also be used. The image data compressed by the compression process is stored as a small sized data in memory, and is expanded by an expansion process according to a predetermined timing.
An image area separation data compression process is a process by which the image area separation data (attribute information) created by the image area separation process is compressed. It is preferable to use a reversible method for compressing the image area separation data, since it is vital to hold the entire data. JBIG (Joint bi-level Image Expert Group) method, for instance, can be employed. The image area separation data (attribute information) compressed by the image area separation data compression process is stored in the memory and is expanded by the image area separation data expansion process in time with the expansion with the image data.
The image data, image area separation data (attribute information) thus compressed in the way described above can be stored, apart from memory, in an auxiliary storage device, taking into account the fact that the image data may require to be transferred outside and saved or processed. The auxiliary storage device should preferably be able to store a large volume of data, such as a hard disk. This is because, unlike the memory which is used for temporary storage, the auxiliary storage device needs to store data for a certain length of duration. By storing the image area separation data (attribute information) in the auxiliary storage device, the image area separation data (attribute information) can be activated for an image, data that input from outside. This will be explained in detail in a later section.
A color correction process converts the image signals read as RGB signals into densities of toner components CMY (cyan, magenta, and yellow).
An under color removal/black generation process removes the amount below the least density from among the component density of CMY as under color and replaces it with K (black) toner density component. This process also switches according to the image area separation data (attribute information), thereby improving the image quality. To be more specific, if the degree of replacement with respect to the minimum density is represented in percentage, that is, if the character area is 100% replaced, the black characters can be reproduced in mostly black, thereby suppressing flaws such as tinting. On the other hand, in the case of the picture area, roughness of texture due to achromatic areas is suppressed as the ratio of replacement is low.
A printer γ correction process converts image signals in accordance with the output characteristics of an image output unit (printer) and gradation characteristics of an intermediate toning process explained later. When the intermediate toning process carries out switching in accordance with the area, the printer γ correction also needs to switch accordingly. In the character area, for instance, the printer γ correction process carries out a binary density change in order to enhance the contrast of the character, and conversely, in the picture area the printer γ correction process carries out a gentle density change.
An intermediate toning process employs a dither process or an error diffusion process, and expresses multinary input gradients by output gradients which are normally fewer. The intermediate toning process also switches between error diffusion process and dither process according to the area. That is, when a character area is encountered, the intermediate toning process employs the error diffusion process to emphasize the resolution, and when a picture area is encountered, the dither process is employed to emphasize the contrast.
A printer section forms an output image according to the input image signals and prints on a paper, etc. The printer section also has functions of reproducing a color image using a four-color toner containing CMYK (cyan, magenta, yellow, and black) and reproducing a black-and-white image using a single-color black toner.
In the example illustrated in
The processes described above, when carried out in the sequence in which they have been described, essentially are the processes of a copier.
It is generally preferable to compress the image data and decrease the data volume when transferring the image data to the outside. Accordingly, as shown in
When a compressed image data is input from outside in order to be output on paper, etc., the image data is first input into the memory and the subsequent processes are the same as those of the copier. This image data is also input in the ID recognizing process. The ID recognizing process involves extraction of the ID data appended to the image data, and based on the ID data, invoking the image area separation data (attribute information) corresponding to the image data from the auxiliary storage device. If the ID data is appended as a header, the extraction method of the ID data may be simply to read the header. If the ID data is embedded as a digital watermark, a method appropriate for the embedding method used may be employed to extract the ID data.
The course of action in the case in which the ID data is not included in the input image data or in the case in which even if the ID data is present, there is no image area separation data (attribute information) having the same ID data is not described here. However, in such cases, a process suitable to the entire picture may be carried out without resorting to the image area separation data (attribute information). Alternatively, as disclosed in the conventional technology (Japanese Patent Laid-Open Publication No. 9-027905), a different image area separation process suitable to the external data may be provided, and the image area separation data (attribute information) may be created with the help of the image area separation process.
Thus, according to the present invention, the created image area separation data (attribute information) is stored. When an image data is input from outside, it is determined if an image area separation data (attribute information) corresponding to the input image data is present or not. If it is determined that the image area separation data (attribute information) corresponding to the input image data is present, processes suitable to each area are carried out.
In other words, according to the present invention, even if an image data is input again after it has been transferred outside can be processed by using an appropriate image area separation data (attribute information). Consequently, a high image quality comparable to that of a copier can be obtained.
Thus, the image processing apparatus according to the present invention includes a attribute information creating unit that creates attribute information that indicate the image characteristics from the image data, a storing unit that stores the attribute information created by the attribute information creating unit, a processing unit that carries out processing of the image data according to the area, a transferring unit that transfers to the outside the image data for which attribute information is created, an input unit that inputs the image data from outside, a specifying unit that determines whether or not the attribute information created from the image data input from outside is stored in the storing unit, and if present, specifies the attribute information, and a processing unit that, if the specifying unit specifies the attribute information for the image data input from outside, carries out the processing using the specified attribute information.
The attribute information creating unit can be made to include an image area separation processing function by which it can determine from the image characteristics whether an area is a character area or a picture area.
Alternatively, the attribute information creating unit can be made to include an image area separation processing function by which it can determine from the image characteristics whether an area is a black character area or a color character area or a picture area.
Alternatively, the attribute information creating unit can be made to include an image area separation processing function by which it can determine from the image characteristics whether an area is a character area or a halftone area or a picture area.
The image processing apparatus according to the present invention may also be provided with an appending unit that appends a specific data (such as an ID data) to the attribute information created from the image data input from outside so that the attribute information can be specified. The specifying unit in this case determines whether the specific data is included in the input image data. If the specific data is present in the image data, the specifying unit extracts the specific data and using the specific data specifies the attribute information.
The appending unit may append the specific data as a header or footer to the image data. Alternatively, the appending unit may embed the specific data in the image data itself.
In the structure illustrated in
The process of inputting from and outputting to outside the image data will be explained next with reference to the example shown in
When transferring the image data outside, unlike the process shown in
The separation accuracy of the second image area separation data (second attribute information) is generally inferior to that of the first image area separation data (first attribute information). This is because, the image data input from outside is irreversibly compressed and the image separation process is often carried out on a low-quality image. Consequently, the image processing yields better results with the first image area separation data (first attribute information) as compared to the second image area separation data (second attribute information). Therefore, the first image area separation data (first attribute information) is specified with the image area separation data comparison process using the method described below.
In other words, the specification method involves comparison of the second image area separation data (second attribute information) created by the second image area separation process with the first image area separation data (first attribute information) stored in the in the auxiliary storage device. If the two data are found to be similar, the first image separation data (first attribute information) is specified.
The subsequent process is carried out using the specified image area separation data (attribute information). If a corresponding first image area separation data (first attribute information) is not found, the process may be carried out using the second image area separation data (second attribute information). Alternatively, without using the image area separation data (attribute information), image processing may be carried out on the entire image without switching processes according to the area.
The second image area separation process or the second image area separation data (second attribute information) may be different from the first image area separation process or the first image area separation data (second attribute information). For instance, only edge detection may be carried out in the second image area separation process, and the first image area separation data (first attribute information) may be specified by confirming that all the pixels that are determined to be character areas in the first image area separation data (first attribute information) have large edge amounts.
Thus, there is provided in the image processing apparatus according to the structure illustrated in
If no attribute information is specified by the specifying unit, then the processing unit carries out the process using the second attribute information.
Alternatively, if no attribute information is specified by the specifying unit, no attribute information is used and the processing unit carries out a uniform process on the image area without discriminating between character areas and picture areas.
Thus, by providing a second image area separation process that accommodates the specifications of the first image area separation, or the image data that is transferred out and edited, the image area separation data (attribute information) can be specified more accurately.
Thus, there is provided in the image processing apparatus according to the structure illustrated in
If no attribute information is specified by the specifying unit, then the processing unit carries out the correction using the second attribute information. Alternatively, if no attribute information is specified by the specifying unit, the processing unit carries out a uniform correction, without using the attribute information, on the entire image area without discriminating between character areas and picture areas.
The central processing unit 21 includes the functions required for the processes and the functions of the units of the present invention as described above.
In other words, the present invention can be offered in the form of programs that make the computer (the central processing unit 21) realize the following functions. Namely, creation of attribute information that indicate the characteristics of an image from the image data, storing of the created attribute information, determining, when an image data is input from outside, if the attribute information created from the input data exist among the stored attribute information, and if present, specifying the attribute information, and processing the image data input from outside using the specified attribute information.
The present invention can further be offered in the form of programs that make a computer (central processing unit 21) realize the following functions by packaging them as a software package (more specifically, in the form of a storage medium such as a CD-ROM and the like), the function being, creation of attribute information that indicate the characteristics of an image from the image data, storing of the created attribute information, determining, when an image data is input from outside, if the attribute information created from the input data exist among the stored attribute information, and if present, specifying the attribute information, and processing the image data input from outside using the specified attribute information.
In other words, the image processing apparatus according to the present invention can be realized by making a general computer system provided with a scanner, printer, etc. read the programs recorded on the recording medium such as a CD-ROM and the like, and by the processing by the microprocessor of the computer system. Thus, the programs required for executing the processes of the present invention (in other words, the programs required by the hardware) are recorded on a storage medium. The storage medium need not necessarily be a CD-ROM and may be read-only memory, random access memory, flexible disk, memory card, etc. The programs recorded on the medium can also be installed on a storage medium built into the hardware system (such as the hard disk 26) and accessed and launched from there. Thus, the processes of the present invention can be realized from the CD-ROM on which the programs required for executing processes are recorded or by installing the programs on the hard disk and launching the programs from the hard disk.
According to the present invention, attribute information (image area separation data) of an image data to be transferred out are stored. When the image data is input again from outside, the attribute information (image area separation data) corresponding to that image data are specified and used. Thus the image data that has once been transferred out can be processed exactly like an image that has never been transferred out. Consequently, a high image quality can be obtained.
A specific data is embedded in the image data itself. Consequently, the versatility of the image data that is transferred out can be preserved. The image data is not tampered with in any way. Consequently, the image quality can be preserved.
Image area separation data can be specified more accurately based on a rigid specification method. Even if attribute information are not stored, appropriate processes according to the image area can be carried out.
Although the invention has been described with respect to a specific embodiment for a complete and clear disclosure, the appended claims are not to be thus limited but are to be construed as embodying all modifications and alternative constructions that may occur to one skilled in the art which fairly fall within the basic teaching herein set forth.
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