IMAGE PROCESSING DEVICE AND IMAGE PROCESSING METHOD

摘要

An image processing device includes: a calculator that calculates a gray scale histogram for each color component of an image signal; a calculator that calculates, for each color component, a maximum and a minimum of classes having a frequency greater than zero in the gray scale histogram; a determiner that generates, for each color component, a histogram having classes each having an absolute difference value between the frequencies of adjacent classes in the gray scale histogram, and compares the absolute difference values in the histograms with a value to determine, from the presence or absence of an absolute difference value exceeding the value, an image type of the image; a generator that generates a gray scale correction curve from the calculated maximum and minimum for each color component; and a corrector that performs gray scale correction on the image signal using the gray scale correction curve.

主权项

1. An image processing device comprising:
a gray scale histogram calculator that calculates, with respect to an image signal having color components and gray scale components and forming an image, a gray scale histogram of the gray scale components for each color component, each gray scale histogram having classes each having a frequency; a maximum/minimum calculator that uses the gray scale histogram for each color component to calculate, for each color component, a maximum and a minimum of classes having a frequency greater than zero in the gray scale histogram; an image type determiner that generates, for each color component, an absolute difference value histogram having classes each having an absolute difference value between the frequencies of adjacent classes in the gray scale histogram, compares the absolute difference values in the absolute difference value histograms with a predetermined threshold value to determine, according to the presence or absence of an absolute difference value exceeding the threshold value, a size of an area of image regions where the gray scale components are uniform, and determines an image type of the image according to the determination; a gray scale correction curve generator that generates a gray scale correction curve for correcting a gray scale of the image signal for each color component, on a basis of a largest and a smallest of the maximum and the minimum of the classes for each color component calculated by the maximum/minimum calculator and the determination of the image type; and a gray scale corrector that uses the gray scale correction curve to perform gray scale correction on the gray scale components of the image signal for each color component, wherein for each color component, the maximum/minimum calculator: calculates, as a first maximum, a class at which an accumulated value exceeds a predetermined proportion of a total frequency of the gray scale histogram, the accumulated value being obtained by accumulating the frequencies from a maximum class toward a minimum class in the gray scale histogram; calculates, as a first minimum, a class at which an accumulated value exceeds a predetermined proportion of the total frequency of the gray scale histogram, the accumulated value being obtained by accumulating the frequencies from the minimum class toward the maximum class in the gray scale histogram; compares the absolute difference values in the absolute difference value histogram with a predetermined threshold value to obtain a minimum of classes having an absolute difference value exceeding the threshold value as a second minimum and a maximum of the classes having an absolute difference value exceeding the threshold value as a second maximum; determines, as the minimum of the classes, a smaller of the first minimum and the second minimum; and determines, as the maximum of the classes, a larger of the first maximum and the second maximum.