Automatic contrast enhancement
First Claim
1. A computer-readable medium storing computer-executable instructions for performing a computer process for automatic contrast correction, the computer process comprising:
- providing digital image data;
representing the data in the form of a brightness histogram;
determining a measure of central tendency for said histogram as a determined measure of central tendency;
adding a shift value to the measure of central tendency to provide an adjusted measure of central tendency;
computing a tone reproduction curve by a ratio containing logarithms of determined and adjusted measures of central tendency; and
applying this tone reproduction curve to brightness values of the image.
11 Assignments
0 Petitions
Accused Products
Abstract
A method of automatic contrast correction comprises providing digital image data, representing the data in the form of a brightness histogram, determining a measure of central tendency for said histogram, adding a shift value to the measure of central tendency to provide an adjusted measure of central tendency, using the both the determined and adjusted measures of central tendency to determine the exponent of a tone reproduction curve, and applying the tone reproduction curve to the brightness values of the image. Additionally, the method may provide further correction by applying to the brightness values of the image an S-shaped tone reproduction curve that does not change a measure of central tendency of the brightness histogram.
96 Citations
24 Claims
-
1. A computer-readable medium storing computer-executable instructions for performing a computer process for automatic contrast correction, the computer process comprising:
-
providing digital image data;
representing the data in the form of a brightness histogram;
determining a measure of central tendency for said histogram as a determined measure of central tendency;
adding a shift value to the measure of central tendency to provide an adjusted measure of central tendency;
computing a tone reproduction curve by a ratio containing logarithms of determined and adjusted measures of central tendency; and
applying this tone reproduction curve to brightness values of the image. - View Dependent Claims (2, 3, 4)
-
-
5. A computer-readable medium storing computer-executable instructions for performing a computer process for contrast correction, the computer process comprising:
-
providing digital image data;
representing the data in the form of a brightness histogram;
determining a measure of central tendency for said histogram; and
applying to brightness values of the image an S-shaped tone reproduction curve that does not change a measure of central tendency of the brightness histogram. - View Dependent Claims (6, 7)
-
-
8. A computer-readable medium storing computer-executable instructions for performing a computer process for automatic contrast correction, the computer process comprising:
-
providing digital image data;
representing the data in the form of a brightness histogram;
determining a measure of central tendency for said histogram; and
applying to brightness values of the image an S-shaped tone reproduction curve that does not change a measure of central tendency of the brightness histogram, wherein the shape of the S-shaped tone reproduction curve is determined by linear regression on the integral brightness histogram.
-
-
9. A computer-readable medium storing computer-executable instructions for performing a computer process for correcting contrast in a digital image, the computer process comprising:
-
determining a histogram of brightness values in the digital image;
determining a measure of central tendency of the histogram;
computing a shift value as a function of the measure of central tendency of the histogram;
applying the shift value to the measure of central tendency to generate a measure of adjusted central tendency;
generating a non-linear transformation based on the measures of central tendency and adjusted central tendency; and
applying the non-linear transformation to the brightness values in the digital image to correct contrast in the digital image. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16)
-
-
17. A method of correcting contrast in a digital image, the method comprising:
-
determining a histogram of brightness values in the digital image;
determining a measure of central tendency of the histogram;
computing a shift value as a function of the measure of central tendency of the histogram;
applying the shift value to the measure of central tendency to generate a measure of adjusted central tendency;
generating a non-linear transformation based on the measures of central tendency and adjusted central tendency; and
applying the non-linear transformation to the brightness values in the digital image to correct contrast in the digital image. - View Dependent Claims (18, 19, 20, 21, 22, 23, 24)
-
Specification