1. Lecture 6
Histogram processing

2. Histogram Specification
Can we design a with given ?
Find the Hist. Eq. for the input image and for the desired pdf:
What are and ?

3. Histogram Specification
Therefore
Check:

4. Histogram Specification
Procedure:
Histogram Equalization
Compute for each r.
Discrete approximation:

5. Histogram Specification

6. Application

7. Application

8. Application

9. Enhancement using local statistics
Histogram processing on a local neighborhood

10. Local statistics
Compare local and global mean to interpret the darkness of a pixel.
Compare local standard deviation and global standard deviation to deduce whether a pixel is on a high contrast region or not.

11. Enhancement based on local statistics
Dark pixels found be comparing global and local means.
Low contrast regions found by comparing local and global std. deviations
Enhance dark pixels with low contrast, but not those lying on a flat region

12. Arithmetic and Logic oeprations
Pixel-by-pixel addition and subtraction
Logic:
Bitwise: AND, OR, NOT

13. Image Subtraction
Subtraction shows what has changed in an image

14. Logical operations