JP3830269B2 - Image correction processing method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image correction processing method used for a laser printer, a digital copying machine, and the like, and in particular, inputs bitmap image data including pixels having multi-value gradations and detects an edge portion of the image. The present invention relates to an image correction processing method for performing image correction processing such as smoothing processing if necessary.
[0002]
[Prior art]
In Japanese Patent Laid-Open No. 9-20550, when a composite image in which a monotone image and a multi-tone image are superimposed is printed by a laser printer, smoothing processing for the contour of the monotone character and faithfulness of the multi-tone image are disclosed. There has been proposed a technique that achieves a desired print result over the entire image while achieving both beautiful reproduction and the like.
[0003]
That is, in FIG. 6, when the composite image 2 is input, each pixel value of the composite image 2 is binarized by the binarization unit 4 to reproduce the monotone image 8, and on the other hand, the multi-tone from the composite image 2 is reproduced. The N double dense image 10 is reproduced.
[0004]
Next, a smoothing process is performed on the monotone image 8 to smoothly correct the outline of the character. Further, the pixel corresponding to the corrected portion 17 of the monotone image 8 of the N double dense image 10 is masked and converted to white data. Thereafter, the final image 22 is obtained by superimposing the smoothed monotone image 16 and the masked N-fold dense image 18. Reference numeral 6 denotes a double-density image processing unit, 12 denotes a smoothing processing unit, 13 denotes a correction signal, 14 denotes a mask processing unit, and 20 denotes a logical sum unit.
[0005]
[Problems to be solved by the invention]
In the above prior art, when the input image has 16 gradation levels from 0h to fh per dot, the pixel to be corrected has a high density (a value close to fh) and a low density (0h). As shown in FIG. 7, the binary data is converted into binary data such that pixels with an arbitrary density or higher are provided with image data, and density lower than that is provided with no data, as shown in FIG. The smoothing correction process is performed on the pixel, and the corrected pixel is output with priority over the pixel that has not been subjected to the correction process, thereby reflecting the correction output result.
[0006]
That is, with respect to a pixel that is a correction target by the smoothing process, the smoothing result is prioritized and the original multi-value data is converted into white data by masking. For this reason, a part of the information of the input image is lost at this point.
As a result, as shown in FIG. 6, a pixel similar to “00” appears as data at the lower right portion of the image where data “01” should be output at an intermediate density. A pixel that is not white in the input data is missing one dot or more.
[0007]
Image jaggies are conspicuous in areas where the pixel contrast is high, that is, the boundary between white dots and black dots, but are less noticeable in multi-valued gradation images. In many cases, reproduction is prioritized and the image looks better.
[0008]
The present invention reduces the processing that adversely affects the gradation reproducibility of a multi-value gradation image by stopping the correction processing function depending on the relationship with surrounding pixels even if the target pixel is subjected to smoothing correction. An object of the present invention is to provide an image correction processing method having functions and excellent multi-level gradation reproducibility.
[0009]
[Means for Solving the Problems]
To achieve the above object, the invention according to claim 1 inputs the image data having a gradation of multivalued, in the image correction processing method for performing image correction processing such Smoothing processing, the target pixel is a smoothing When there is a first processing step for determining whether or not there is a correction target pixel, a second processing step for determining whether or not there is a pixel having an intermediate density gradation around the correction target pixel, and an intermediate density pixel outputs input image data to, if there is no pixel in the intermediate concentration is characterized in that it has a, a third processing step of outputting the image data after the smoothing processing.
[0010]
To achieve the above object, an invention according to claim 2, wherein, inputting image data having gradation of multi-value, in the image correction processing method for performing image correction processing such Smoothing processing, the target pixel is smoothed a first processing step of determining whether the correction target pixel or not of the correction target pixel has a concentration of more than the white data, and binarization of the result is white dots for determining whether or not the second process step when, by the second process step, the correction target pixel Chi lifting a concentration of more than the white data, and, if the binarized result is determined to be a white dot, and outputs the input image data, it is characterized in further comprising a third step of outputting the image data after the smoothing processing, the in other cases [0011]
In order to achieve the above object, according to a third aspect of the present invention, in the image correction processing method according to the second aspect, in the second processing step, either the upper or lower side or the left or right side of the correction target pixel. It is determined whether other correction target pixels are arranged, and when the other correction target pixels are arranged, the input image data is output. The invention according to claim 4 is a computer-readable storage medium storing a program for executing the method according to any one of claims 1 to 3.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
First, a first embodiment will be described.
FIG. 1 is a diagram illustrating an example of a pixel of interest and an intermediate density detection region around it, and FIG. 2 is a flowchart illustrating a first image correction processing example.
In FIG. 1, reference numeral 101 denotes a target pixel, and 102 denotes an intermediate density detection area (reference area).
[0013]
In FIG. 2, it is first determined whether or not the target pixel 101 is a correction target pixel (S1). If the target pixel 101 is a correction target pixel (YES in S1), it is next determined whether or not there is an intermediate density pixel in the intermediate density detection region 102 around the target pixel 101 (S2).
[0014]
That is, it is determined whether or not there is a pixel having an intermediate density in the intermediate density detection area 102 that is greater than or equal to no density data (0h) and is determined to have no image data at the time of binarization (S2). If this low-level intermediate density pixel exists (YES in S2), the pre-smoothing correction data, that is, the density data of the input image is output prior to the corrected image data (S3).
[0015]
If there is no intermediate density pixel in the intermediate density detection area (NO in S2), the smoothing process is performed as before (S4).
[0016]
Next, a second embodiment will be described.
In the process of the first embodiment, the region for detecting the intermediate density pixel is expanded to a region other than the periphery of the target pixel 101, and it is determined whether or not the correction target pixel is in the collection of intermediate density pixels. If it exists in the intermediate density pixel, priority is given to the reproducibility of the density gradation expression, so that the input pixel data is output prior to the smoothing correction process or the smoothing function is not operated.
[0017]
Next, a third embodiment will be described.
FIG. 3 is a flowchart showing a second image correction processing example.
When the target pixel (target pixel) 101 is determined to be a correction target pixel (YES in S11), the density data of the target pixel 101 has a density equal to or higher than 0h (white data) that is a density detection threshold (YES in S12). In the case of an intermediate density that is determined to have no data (white dots) at the time of binarization (YES in S13), an input pixel that has not been subjected to smoothing processing regardless of the image density of surrounding pixels Pixel data is output at the data density (S14).
[0018]
In the case of N in S12 and N in S13, the smoothing process is performed as before (S15).
[0019]
Next, a fourth embodiment will be described. FIG. 4 is a diagram showing a first example of the correction target pixel and the surrounding intermediate density detection region, and FIG. 5 is a diagram showing a second example. When it is determined that the target pixel 101 is the correction target pixel 103, it is determined whether another correction target pixel ( correction processing data ) is arranged on the upper or lower side or the left or right side of the smoothing correction target pixel. As shown in FIG. 4, when correcting a vertical boundary line, the correction target pixels are arranged in the vertical direction. In this case, if there is an intermediate density pixel that has a density greater than or equal to white data in the vertical direction of the correction target pixel 103 and is determined to have no data at the time of binarization, smoothing processing is performed. Pixel data is output at a non-input pixel data density.
[0020]
Further, in the case of a border line close to the horizontal, as shown in FIG. 5, the input pixels arranged in the left-right direction of the correction target pixel 103 are referred to, and the same processing as in the vertical case is performed.
[0021]
【The invention's effect】
According to the first aspect of the present invention, when there is an intermediate density pixel around the correction target pixel, the input data is printed as it is, in other words, the edge smoothing processing of the image is not performed, so that the image image is displayed. Image correction processing giving priority to density gradation reproducibility can be performed while avoiding image correction processing that has an adverse effect.
[0023]
According to the second aspect of the present invention, when the correction target pixel is a low density image, the gradation of the low density pixel around the high density pixel is corrected data by not performing the smoothing process. It is possible to prevent the change and improve the gradation reproducibility of the image. Further, in this case, the area for determination is only one dot of the target pixel, and the circuit configuration can be simplified.
[0024]
According to the invention described in claim 3 , the same effect as that of the invention described in claim 2 can be obtained by referring to the intermediate density detection region only in a specific direction by the arrangement of the pixels around the correction target pixel, and at the same time, the circuit The configuration can be made feasible on a smaller scale.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating an example of a target pixel and an intermediate density detection region around it.
FIG. 2 is a flowchart illustrating a first image correction processing example.
FIG. 3 is a flowchart illustrating a second image correction processing example.
FIG. 4 is a diagram illustrating a first example of a correction target pixel and an intermediate density detection region around the correction target pixel.
FIG. 5 is a diagram illustrating a second example of a correction target pixel and an intermediate density detection region around the correction target pixel.
FIG. 6 is a block diagram of a conventional image correction process.
FIG. 7 is a diagram illustrating an example of a conventional image correction process.
[Explanation of symbols]
101 Target pixel 102 Intermediate density detection region 103 Correction target pixel

Claims (4)

In an image correction processing method for inputting image data having multi-value gradations and performing image correction processing such as smoothing processing,
A first processing step for determining whether the target pixel is a pixel to be corrected for smoothing;
A second processing step of determining whether or not there is a pixel having an intermediate density gradation around the correction target pixel;
A third processing step of outputting the input image data when there is an intermediate density pixel, and outputting the image data after the smoothing process when there is no intermediate density pixel;
An image correction processing method characterized by comprising: In an image correction processing method for inputting image data having multi-value gradations and performing image correction processing such as smoothing processing,
A first processing step for determining whether the target pixel is a pixel to be corrected for smoothing;
A second processing step of determining whether or not the correction target pixel has a density equal to or higher than white data and whether the binarization result is a white dot;
When it is determined by the second processing step that the correction target pixel has a density equal to or higher than white data and the binarization result is white dots, the input image data is output, And a third step of outputting the image data after the smoothing process in some cases. In the second processing step,
Further, it is determined whether another correction target pixel is arranged on the upper or lower side or the left or right side of the correction target pixel, and when the other correction target pixel is arranged, the input image data is output.
The image correction processing method according to claim 2. The computer-readable storage medium which memorize | stored the program for performing the method as described in any one of Claims 1-3 .

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