Automatic contrast correction device and automatic contrast correction method
First Claim
1. An automatic contrast correction device for receiving an input image including two-dimensionally arranged luminance information, and automatically correcting a contrast of the input image to generate a corrected output image, comprising:
- a frequency distribution counter for obtaining a frequency distribution of the input image for each luminance value thereof;
a nonlinear converter for receiving a frequency distribution from the frequency distribution counter, and converting a frequency for each luminance based on one of a nonlinear function and a nonlinear table to generate a nonlinear frequency distribution;
an accumulation converter for accumulating the nonlinear frequency distribution from the nonlinear converter to generate a gradation conversion characteristic;
a gradation converter for converting the input image based on the gradation conversion characteristic from the accumulation converter; and
a controller for controlling entire status and timing.
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Abstract
Provided are an automatic contrast correction device and an automatic contrast correction method for a pictorial image constituted by luminance values for two-dimensionally arranged pixels capable of performing automatic correction to obtain a suitable contrast to human eyes corresponding to perception in a human brain. In order to obtain an optimized gradation characteristic for conversion, a frequency distribution is nonlinearly converted corresponding to a nonlinear perception of stimulus in a human brain to become flat. The conversion can generally keep an original characteristic of a picture having a good appearance to human eyes.
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Citations
14 Claims
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1. An automatic contrast correction device for receiving an input image including two-dimensionally arranged luminance information, and automatically correcting a contrast of the input image to generate a corrected output image, comprising:
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a frequency distribution counter for obtaining a frequency distribution of the input image for each luminance value thereof;
a nonlinear converter for receiving a frequency distribution from the frequency distribution counter, and converting a frequency for each luminance based on one of a nonlinear function and a nonlinear table to generate a nonlinear frequency distribution;
an accumulation converter for accumulating the nonlinear frequency distribution from the nonlinear converter to generate a gradation conversion characteristic;
a gradation converter for converting the input image based on the gradation conversion characteristic from the accumulation converter; and
a controller for controlling entire status and timing. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. An automatic contrast correction method for receiving an input image including two-dimensionally arranged luminance information, and automatically correcting a contrast of the input image to generate an corrected output image, comprising:
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generating a frequency distribution of the input image for each luminance value by counting a number of pixels having a same luminance value;
converting each frequency of the frequency distribution for each luminance based on one of a nonlinear function and a nonlinear table to generate a nonlinear frequency distribution;
accumulating the nonlinear frequency distribution to generate a gradation conversion characteristic; and
converting the input image according to the gradation conversion characteristic. - View Dependent Claims (9, 10, 11, 12, 13, 14)
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Specification