Dynamic histogram warping of image histograms for constant image brightness, histogram matching and histogram specification

• US 5,727,080 A
• Filed: 05/03/1995
• Issued: 03/10/1998
• Est. Priority Date: 05/03/1995
• Status: Expired due to Term

• Current Assignee: NEC Corporation
• Original Assignee: NEC Research Institute, Inc. (NEC Corporation)
• Inventors: Roy, Sebastien, Cox, Ingemar J.
• Primary Examiner(s): COUSO, YON JUNG
• Application Number:
  US08/434,085
• Time in Patent Office: 1,042 Days
• Field of Search: 382/168, 382/169, 382/274, 382/276, 358/455, 358/461, 345/147
• US Class Current: 382/168
• CPC Class Codes: G06T 2207/10024 Color image
• CPC Class Codes: G06T 2207/10036 Multispectral image; Hyperspectral image
• CPC Class Codes: G06T 5/40 using histogram techniques
• CPC Class Codes: G06T 5/50 using two or more images, e.g. averaging or subtraction
• CPC Class Codes: G06T 5/92 based on global image properties

Abstract

Dynamic histogram warping is performed on histograms extracted from an image pair of a scene. The warped histograms are remapped to the image pair and the resulting remapped image pair is subsequently subjected to image processing.

Claims

1. An apparatus for dynamic histogram warping of image pairs comprising:

an imager for providing an image pair of a scene;

computer coupled to said imager for receiving said image pair of a scene and extracting the histograms of the images, subjecting the histograms to dynamic histogram warping and then remapping the image according to the warped histogram, where said computer determines the minimum total cost of a matching according to;

##EQU4## where D is the total cost, M and N are the maximum allowable compression of the histograms, m and n are the intensity values of the first image and the second image of the image pair of the scene, d_k,l is the cost of a k-to-l mapping, for generating an image or image pair having specified histogram characteristics; and

image processor coupled to said computer for receiving said remapped image or image pair and processing said remapped image pair.

2. An apparatus for dynamic histogram warping of image pairs as set forth in claim 1, where said image pair of a scene are stereo images of a stationary scene.

3. An apparatus for dynamic histogram warping of image pairs as set forth in claim 1, where said image pair of a scene is a motion sequence.

4. An apparatus for dynamic histogram warping of image pairs as set forth in claim 1, where one image of said image pair is a histogram specification.

5. A method of dynamic histogram warping of image pairs comprising the steps of:

providing an image pair of a scene;

extracting the histograms of the images;

performing dynamic histogram warping of said extracted histograms by determining the minimum total cost of a matching according to;

##EQU5## where D is the total cost, M and N are maximum allowable compression of the histograms, m and n are the intensity values of the first image and the second image of the image pair of a scene, d_k,l is the cost of a k-to-l mapping;

remapping the images according to the warped histograms; and

processing the remapped image pair.

6. A method of dynamic histogram warping of image pairs as set forth in claim 5, where said providing an image pair of a scene provides stereo images of a stationary scene.

7. A method of dynamic histogram warping of image pairs as set forth in claim 5, where said providing an image pair of a scene provides a motion sequence.

8. A method of dynamic histogram warping of image pairs as set forth in claim 5, where said providing an image pair comprises providing a histogram specification.