Image processing apparatus and method for binarizing a multilevel image
First Claim
Patent Images
1. An image processing apparatus, comprising:
- a background judgment device judging whether a target pixel is a background pixel using a gray level difference and a standard deviation of gray levels of pixels in a vicinity area of the target pixel on receipt of a multilevel image, whereinthe gray level difference is an amount which is calculated based on a difference between an average gray level of white pixels in the vicinity area of the target pixel and an average gray level of black pixels in the vicinity area of the target pixel; and
a local binarization device locally binarizing the target pixel and outputting a binary image if it is judged that the target pixel is not the background pixel.
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Abstract
It is judged for each pixel in an inputted multilevel image whether the pixel is a background pixel, and the pixel is locally binarized if it is judged not to be a background pixel. Then, it is judged whether the pixel belongs to a background or a stroke, such as of a character, ruled line, etc., and a binary image is generated.
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Citations
28 Claims
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1. An image processing apparatus, comprising:
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a background judgment device judging whether a target pixel is a background pixel using a gray level difference and a standard deviation of gray levels of pixels in a vicinity area of the target pixel on receipt of a multilevel image, wherein the gray level difference is an amount which is calculated based on a difference between an average gray level of white pixels in the vicinity area of the target pixel and an average gray level of black pixels in the vicinity area of the target pixel; and a local binarization device locally binarizing the target pixel and outputting a binary image if it is judged that the target pixel is not the background pixel. - View Dependent Claims (2, 3, 4, 5, 6, 7, 9, 10, 12, 13, 14, 15, 16, 17, 18, 19)
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8. An image processing apparatus, comprising:
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a background judgment device judging for each target pixel whether the target pixel is a background pixel on receipt of a multilevel image, and a local binarization device locally binarizing the target pixel, judging which of a background and a stroke the target pixel belongs to, and outputting a binary image if it is judged that the target pixel is not the background pixel, wherein said background judgment device judges whether the target pixel is the background pixel using standard deviation of gray levels and a gray level difference of pixels in a vicinity area of the target pixel, and wherein said background judgment device judges whether the target pixel is the background pixel under a background judgment condition of r=σ
/Δ
g<
r min with σ
as the standard deviation in the vicinity area of the target pixel, Δ
g as the gray level difference in the vicinity of the target pixel and rmin as a prescribed constant.
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11. An image processing apparatus, comprising:
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a background judgment device judging for each target pixel whether the target pixel is a background pixel on receipt of a multilevel image, and a local binarization device locally binarizing the target pixel, judging which of a background and a stroke the target pixel belongs to, and outputting a binary image if it is judged that the target pixel is not the background pixel, wherein said background judgment device judges whether the target pixel is the background pixel using standard deviation of gray levels and a gray level difference of pixels in a vicinity area of the target pixel, and wherein said background judgment device judges whether the target pixel is a background pixel using a combination of a background judgment conditions σ
<
σ
min, r=σ
/Δ
g<
rmin and Δ
g<
Δ
gmin with σ
as the standard deviation in the vicinity area of the target pixel, Δ
g as the gray level difference in the vicinity of the target pixel and σ
min, rmin and Δ
gmin as a prescribed constant.
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20. An image processing apparatus, comprising:
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judging for each target pixel whether a target pixel is a background pixel using a gray level difference and a standard deviation of gray levels of pixels in a vicinity area of the target pixel on receipt of a multilevel image, wherein the gray level difference is an amount which is calculated based on a difference between an average gray level of white pixels in the vicinity area of the target pixel and an average gray level of black pixels in the vicinity area of the target pixel; and locally binarizing the target pixel and outputting a binary image if it is judged that the target pixel is not the background pixel. - View Dependent Claims (21, 22)
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23. A computer-readable storage medium on which is recorded a program for enabling a computer extracting a stroke included in an inputted multilevel image to perform a process, said process comprising:
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judging for each target pixel whether a target pixel is a background pixel using a gray level difference and a standard deviation of gray levels of pixels in a vicinity area of the target pixel on receipt of a multilevel image, wherein the gray level difference is an amount which is calculated based on a difference between an average gray level of white pixels in the vicinity area of the target pixel and an average gray level of black pixels in the vicinity area of the target pixel; and locally binarizing the target pixel and outputting a binary image if it is judged that the target pixel is not the background pixel. - View Dependent Claims (24, 25)
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26. An image processing apparatus, comprising:
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input means for receiving a multilevel image; and background judgment means for judging whether a target pixel is a background pixel using a gray level difference and a standard deviation of gray levels of pixels in a vicinity area of the target pixel;
whereinthe gray level difference is an amount which is calculated based on a difference between an average gray level of white pixels in the vicinity area of the target pixel and an average gray level of black pixels in the vicinity area of the target pixel; and local binarizatiod means for locally binarizing the target pixel and outputting a binary image if it is judqed that the target pixel is not the background pixel.
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27. A transmission signal transmitting to a computer, which extracts a stroke included in an inputted multilevel image, a program for enabling the computer to perform a process, said process comprising:
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judging for each target pixel whether a target pixel is a background pixel using a gray level difference and a standard deviation of gray levels of pixels in a vicinity area of the target pixel on receipt of a multilevel image, wherein the gray level difference is an amount which is calculated based on a difference between an average gray level of white pixels in the vicinity area of the target pixel and an average gray level of black pixels in the vicinity area of the target pixel; and locally binarizing the target pixel and outputting a binary image if it is judged that the target pixel is not the background pixel.
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28. An image processing method, comprising:
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receiving a multilevel image; measuring an average gray level of white pixels in the vicinity area of the target pixel of the multilevel image; measuring an average gray level of black pixels in the vicinity area of the target pixel; calculating a gray level difference based on a difference between the average gray level of white pixels and the average gray level of black pixels in the vicinity area of the target pixel; and judging whether the target pixel is a background pixel using the gray level difference and a standard deviation of gray levels of pixels in the vicinity area of the target pixel.
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Specification