JP3863966B2 - Image processing apparatus and image processing method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image processing apparatus and an image processing method used for a facsimile or the like.
[0002]
[Prior art]
Conventionally, in this type of apparatus, when a color multi-valued image is expressed in a pseudo halftone in a recording system, an error diffusion process for diffusing binarization errors into a peripheral image is generally performed as in the case of a monochrome multi-valued image. Has been used. The error diffusion process is performed by diffusing error data, which is an error between input image data and output image data when the input image data is binarized, into image data of peripheral pixels, so that the input image data in the local region This is a process for making the total density equal to the total density of the output image. Here, in the display system of the pseudo halftone expression, the basic colors of the display system (for example, three colors of cyan (C), magenta (M), and yellow (Y)) are arranged so as not to overlap each other as much as possible. Is common. This arrangement is such that the ratio of error diffusion to surrounding image data during error diffusion (pattern of distribution ratio of errors to surrounding image data) differs for cyan, magenta, and yellow constituting the same pixel data. Realized by processing.
[0003]
For example, this processing is performed by randomizing the order of A, B, and C, assuming that the diffusion ratio of the peripheral image data for error diffusion is three patterns of A, B, and C.
[0004]
On the other hand, it is common that a monochrome image is included in a color image, and conventionally, an error diffusion pattern has been randomized for this monochrome image.
[0005]
[Problems to be solved by the invention]
However, if the error diffusion pattern is randomized for a monochrome image as in the above-described prior art, the dots of cyan, magenta, and yellow in the display system do not overlap so as to be highlighted. That is, the density of cyan, magenta, and yellow increases in the dark portion, and the rate of overlapping of each dot increases, but conversely, the density of cyan, magenta, and yellow decreases in the highlight portion, and each dot overlaps. Since the rate is low, there is a problem that an image region that is a monochrome image but does not become an achromatic color is generated, and the image quality is deteriorated.
[0006]
The present invention has been made in view of such problems, and an image processing apparatus and an image processing method capable of avoiding deterioration in image quality without causing a color tone in a monochrome image during error diffusion processing. The purpose is to provide.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, according to the first aspect of the present invention, there is provided image data determination means for determining whether multivalued image data displayed by a plurality of basic colors not including black is color or monochrome. When the multi-value image data is determined to be color by the image data determination means, the distribution of errors is changed for each basic color , and when the multi-value image data is determined to be monochrome, for each basic color which includes the error distribution means which do not alter the distribution of the error, the error diffusion processing means for converting the multivalued image data into binary image data by error diffusion processing by the distribution of the error from the error distribution means, the It is .
[0008]
For this configuration, the error distribution of the peripheral pixels when the binary, which changed to the basic colors in the case of a color image, it is possible to prevent change in the basic colors in the case of monochrome images, In a monochrome image, each pixel can be overlapped to eliminate the color, and deterioration of image quality can be avoided.
[0009]
According to a second aspect of the present invention, there is provided the image processing apparatus according to the first aspect, further comprising instruction input means for a user to input whether the multi-valued image data is color or monochrome, and the error distribution The means is characterized in that error distribution is performed by selectively selecting either the instruction input or the determination result by the image data determination means .
[0010]
With such a configuration, in the error diffusion process, the user can in advance indicate whether the multi-valued image data is a color image or a monochrome image, so there is no need to make this determination inside the apparatus. Thus, the error diffusion process can be performed quickly. It is also possible to cause the image processing apparatus to determine whether it is color or monochrome.
[0011]
The invention of claim 3, wherein the multi-value image data to determine whether a monochrome or a color displayed by the plurality of basic colors containing no black, this determination, multivalued image data is changing the error distribution of each basic color when it is determined that the color, for each basic color when multivalued image data is determined as a monochrome without changing the distribution of errors, the multi-valued image data of The data is converted into binary image data by error diffusion processing based on this error distribution.
[0012]
For this configuration, the error distribution of the peripheral pixels when the binary, which changed to the basic colors in the case of a color image, it is possible to prevent change in the basic colors in the case of monochrome images, In a monochrome image, each pixel can be overlapped to eliminate the color, and deterioration of image quality can be avoided.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be specifically described with reference to the drawings.
[0014]
(Embodiment 1)
FIG. 1 is a block configuration diagram of Embodiment 1 of an image processing apparatus of the present invention.
In FIG. 1, the image processing apparatus according to the present invention determines the input terminal 1 for color multivalued image data from a scanner or the like and whether the target image data for error diffusion processing is a monochrome image or a color image. And a random number generation unit 3 that determines a distribution pattern of errors to peripheral images, an error diffusion processing unit 4, and an output terminal 5 for binarized image data, which are connected to an image display system. ing.
[0015]
The operation of the image processing apparatus configured as described above will be described. Here, the image data input from the input terminal 1 is so-called dot-sequential data arranged in order of cyan, magenta, and yellow for each pixel.
[0016]
The determination unit 2 determines whether the image data input from the input terminal 1 is a color image or a monochrome image. In this determination, if all the image data of cyan, magenta, and yellow constituting one pixel are all the same value, it is determined to be monochrome. Otherwise, it is determined to be color image data. The flow of determination in the determination unit 2 will be described with reference to FIG.
[0017]
FIG. 2 is a flowchart showing a flow in which the determination unit 2 determines whether the target image data is color or monochrome.
Determination of whether the target image data is a color image or a monochrome image is started by an operation start signal (not shown) (step 1).
[0018]
Next, N = 0 is set for image data constituting one pixel (step 2). A strobe signal is output from the scanner unit together with the image data as a sample timing signal for the image data (step 3). The value of N at this time is stored in the memory as X (N) (step 4).
[0019]
Next, when N = N + 1 (step 5), it is determined whether N = 3 (step 6). If N = 3, the process returns to step 3, and X (N + 1) is stored in the memory. Store. If N = 3, go to Step 7. In step 7, the values of X (0), X (1), and X (2) are compared. If all of these values are equal, it is determined that the image data is monochrome. In this case, the process proceeds to the flowchart in FIG. On the other hand, if even one of the values of X (0), X (1), and X (2) is different, it is determined as a color image, and in this case, the process proceeds to the flowchart in FIG.
[0020]
Next, an error diffusion process when the determination result of the determination unit 2 in FIG. 1 is monochrome will be described with reference to FIG.
[0021]
In FIG. 3, first, N indicating target image data is set to N = 0 (step 8), and cyan image data is acquired (step 9). Next, it is determined whether or not N = 0 (step 10). If N = 0, random numbers are generated for the C image data which is the first image data of one pixel (step 11).
[0022]
The random number generated for the cyan image data is held for one pixel by the random number generator 3. The number of random numbers generated by the random number generator 3 is the same as the number of error distribution patterns. For example, if there are three error distribution patterns, 0, 1 or 2 is randomly generated.
[0023]
The error distribution rate is determined by the random number (step 13), and error diffusion processing is performed by the determined error distribution rate (step 14). Next, it is determined whether or not N = 2 (step 15). If N = 2, unprocessed image data remains. Therefore, 1 is added to the value at this time, and this is replaced with new N. (Step 16). As a result, N = 1 and magenta image data is acquired (step 9). In step 10, the current N is determined and N = 1, so that the process proceeds to step 12. If N = 2, the data is output to the outside (step 17), and the process ends (step 18).
[0024]
Next, the error diffusion process when the determination result of the determination unit 2 in FIG. 1 is color will be described with reference to FIG.
In FIG. 4, first, cyan is set to N = 0 (step 19), and the image data is acquired (step 20). In the case of color, random numbers are generated for all of cyan, magenta, and yellow (step 21). Next, the random number is output to the error diffusion processing unit 4, and error diffusion processing is performed by distributing errors corresponding to the random value (step 22). Steps 23 to 26 are the same as in the case of the monochrome described above, and thus description thereof is omitted.
[0025]
As described above, the error distribution pattern in the error diffusion processing unit 4 in FIG. 1 is randomized by random numbers newly generated for each of cyan, magenta, and yellow when the pixel to be processed is a color image. . On the other hand, in the case of a monochrome pixel, it is the same as cyan image data that is the first image data of one pixel.
[0026]
(Embodiment 2)
FIG. 5 is a block diagram showing the second embodiment and is an example of an apparatus having a reading / recording function including the image processing apparatus according to the present invention. The second embodiment includes an image processing unit 51, a scanner unit 52, a printer unit 53, a panel unit 54, and a main control unit 55. As described above, the image processing unit 51 determines whether the image data is a color image or a monochrome image. In the second embodiment, whether the target image data for error diffusion processing is a monochrome image or a color image. The panel unit 54 includes a switch (not shown) for selectively instructing whether the image is an image, and the main control unit 55 controls the input of this instruction. By this control, determination in the image processing unit 51 can be omitted, so that error diffusion processing can be performed promptly.
[0027]
【The invention's effect】
As is apparent from the above description, according to the present invention, in the error diffusion processing, the error distribution to the peripheral pixel data is performed in the case of a monochrome image, and a plurality of basic colors that do not include black constituting one pixel. In the case of a color image, each pixel data can be random for each image data of a plurality of basic colors that do not include black. The color can be eliminated by superimposing and deterioration of the image quality can be avoided.
[Brief description of the drawings]
FIG. 1 is a block diagram of an image processing apparatus according to Embodiment 1 of the present invention. FIG. 2 is a flowchart showing color determination processing according to the invention. FIG. 3 is a flowchart showing error diffusion processing in the case of a monochrome image. FIG. 4 is a flowchart showing error diffusion processing in the case of a color image. FIG. 5 is a block configuration diagram of an apparatus including an image processing apparatus according to Embodiment 2 of the present invention.
1 Input terminal 2 Judgment unit 3 Random number generation unit 4 Error diffusion processing unit 5 Output terminal

Claims (3)

Image data determination means for determining whether the multi-value image data displayed by a plurality of basic colors not including black is color or monochrome, and the multi-value image data is determined to be color by the image data determination means. If determined, error distribution is changed for each basic color, and if multi-value image data is determined to be monochrome, error distribution means that does not change error distribution for each basic color , and multi-value image data An error diffusion processing means for converting the image data into binary image data by error diffusion processing based on error distribution from the error distribution means . Whether multivalued image data is monochrome or a color has an instruction input means for users to input instruction said error distribution means-option one of the determination result by the instruction input or the image data determining means The image processing apparatus according to claim 1, wherein error distribution is performed by selecting one of them. It is determined whether the multi-value image data displayed with a plurality of basic colors not including black is color or monochrome, and if this determination determines that the multi-value image data is color, the basic color The error distribution is changed every time, and when the multi-value image data is determined to be monochrome, the error distribution is not changed for each basic color , and the multi-value image data is converted into 2 by error diffusion processing based on this error distribution. An image processing method for converting image data into values .

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