×

Image enhancing method using mean-separate histogram equalization and a circuit therefor

  • US 5,963,665 A
  • Filed: 03/10/1997
  • Issued: 10/05/1999
  • Est. Priority Date: 03/09/1996
  • Status: Expired due to Fees
First Claim
Patent Images

1. A method for enhancing an image by histogram-equalizing an input image signal represented by a predetermined number of gray levels, said method comprising:

  • calculating a mean level of the input image;

    grouping a plurality of pixels of said input image signal into a plurality of groups of image in accordance with the gray level of each of said pixels, wherein division of the input image signal into a plurality of groups of image occurs in accordance with the mean level;

    calculating a cumulative density function for each group of image; and

    histogram-equalizing each group of image independent of the other groups of image by mapping an input sample of the group of image into a new gray level based on the cumulative density functions;

    wherein the number of groups of images per each frame of the input image signal is predetermined to be two; and

    wherein said histogram-equalizing comprises;

    mapping the input sample into a first gray level by using a first transform function, wherein the first transform function is based on one of the cumulative density functions and the first gray level is in a first range;

    mapping the input sample into a second gray level by using a second transform function, wherein the second transform function is based on another of the cumulative density functions and the second gray level is in a second range;

    comparing the input sample with the mean level; and

    selecting one of said first and second gray levels according to the comparison of he input sample with the mean level.

View all claims
  • 1 Assignment
Timeline View
Assignment View
    ×
    ×