Patent ID: 8089560

Claim:
An image processing apparatus for performing a luminance correction process of an input image by performing a luminance conversion process on input luminance data; the image processing apparatus comprising: a correction interval setting unit for setting a correction interval which is a range of luminance level for performing the luminance correction process; a correction interval dividing unit for dividing the correction interval into two intervals of a black side interval having low luminance level and a white side interval having high luminance level; histogram calculating units for calculating a total number of luminance histograms of the black side interval and a total number of luminance histograms of the white side interval, respectively; gain setting units for setting a gain of a gamma curve for raising the luminance based on the calculated total number of luminance histograms of the black side interval and a gain of a gamma curve for lowering the luminance based on the calculated total number of luminance histograms of the white side interval, respectively; gamma curve generating units for generating a gamma curve for raising the luminance based on the gain of the curve for raising the luminance, and generating a gamma curve for lowering the luminance based on the gain of the curve for lowering the luminance, respectively; wherein the gamma curve for raising the luminance is expressed with Equation (1) where X is an input luminance value and gam_upper [X] is an output luminance value after luminance conversion; the gamma curve for lowering the luminance is expressed with Equation (2) where X is the input luminance value, and gam_lower[X] is an output luminance value after luminance conversion; and gam_upper ⁡ [ X ] = gain_upper × ( X - end ) × ( start - X ) 256 × ( start - end ) ( 1 ) gam_lower ⁡ [ X ] = - gain_lower × ( X - end ) × ( start - X ) 256 × ( start - end ) ( 2 ) in Equations (1) and (2), gain_upper: gain of the gamma curve for raising the luminance gain_lower: gain of the gamma curve for lowering the luminance start: input luminance value for starting the luminance conversion process end: input luminance value for terminating the luminance conversion process; a gamma curve combining unit for combining the gamma curve for raising the luminance and the gamma curve for lowering the luminance; and a luminance conversion unit for performing the luminance conversion process on the input luminance data in the correction interval using the combined gamma curve.