JP2008113446A5 - - Google Patents

Claims (5)

A feature amount calculating means for calculating a feature amount for an original image which is a digital image;
A character region extracting means for extracting a character region from the original image based on the feature amount;
Block dividing means for dividing the original image into blocks;
Class classification means for classifying the pixels belonging to the character area into a first class and a second class according to color for each block;
Black character color / background color estimation means for estimating a black character color and a background color on the original image based on a class classification of pixels belonging to the character region;
Gradation correction means for performing gradation correction on the original image based on the estimated black character color and background color;
Comprising
The black character color / background color estimation means includes:
Based on the classification result for each block, the first block in the block in which the difference between the average luminance of the pixel group belonging to the first class and the average luminance of the pixel group belonging to the second class is maximized. An image processing apparatus for estimating an average color of a pixel group belonging to the second class in the block in which the average color of the pixel group belonging to the class is a black character color and having the maximum number of pixels belonging to the second class as a background color . Comprising low-resolution image generation means for generating a low-resolution image having a lower resolution than the original image,
The feature amount calculating means includes:
Calculating features from the low resolution image;
The image processing apparatus according to claim 1, wherein the character region extraction unit extracts the character region from the low-resolution image . Interpreted by the computer,
A feature amount calculation function for calculating a feature amount for an original image which is a digital image;
A character region extraction function for extracting a character region from the original image based on the feature amount;
A block division function for dividing the original image into blocks;
A class classification function for classifying pixels belonging to the character area into a first class and a second class according to color, for each block;
A black character color / background color estimation function for estimating a black character color and a background color on the original image based on a class classification of pixels belonging to the character region;
A gradation correction function for performing gradation correction on the original image based on the estimated black character color and background color, and
Based on the classification result for each block, the difference between the average luminance of the pixel group belonging to the first class and the average luminance of the pixel group belonging to the second class is obtained by the black character color / background color estimation function. The average color of the pixel group belonging to the first class in the block having the maximum is a black character color, and the average of the pixel group belonging to the second class in the block having the maximum number of pixels belonging to the second class An image processing program that estimates colors as background colors . Causing the computer to execute a low-resolution image generation function for generating a low-resolution image having a lower resolution than the original image;
The feature amount calculation function calculates the feature amount from the low-resolution image,
The image processing program according to claim 3, wherein the character region is extracted from the low-resolution image by the character region extraction function . A storage medium for storing the image processing program according to claim 3 in a computer-readable manner.