Patent ID: 8339518

Claim:
A video signal processing method comprising the steps of: extracting low-frequency components of a luminance signal from an input video signal at frequencies equal to or lower than a reference frequency, for pixels contained in a specific area of an image carried by the input video signal; allocating the low-frequency components of the luminance signal to a plurality of gradation levels that range from maximum to minimum luminance levels exhibited by the luminance signal to produce luminance histogram data that indicates the distribution of the gradation levels for the pixels; allocating the gradation levels to the pixels based on the luminance signal to produce high-frequency component histogram data that indicates the distribution of the gradation levels for specific pixels among the pixels, the specific pixels carrying high frequency components of the luminance signal, the high-frequency components being equal to or higher than a reference high frequency; correcting the luminance histogram data in accordance with the distribution of the gradation levels in the high-frequency component histogram data to produce corrected luminance histogram data; producing a gradation correction curve for correcting the gradation exhibited by the input video signal using the corrected luminance histogram data; and correcting the low-frequency components of the luminance signal of the input video signal based on the gradation correction curve, with no correction of the high-frequency components of the luminance signal.