MATLAB code of Image Negation and Image Enhancement using Histogram Equilization.

Image Negation:

The negative point transformation function also known as contrast reverse. The negative transformation is used to make the output more suitable for the task at hand (e.g., by making it easier to notice interesting details in the image).

Where‘s’ is Output image after transformation

L-1 is Maximum Pixel value

r is Input Image.

Fig: Negative Image Transformation

This kind of transformation used for finding details in X-ray Images. It will gives white details in black area and black details in white area.

Histogram Equalization: 

Histogram equalization is a technique by which the gray-level distribution of an image is changed in such a way as to obtain a uniform (flat) resulting histogram, in which the percentage of pixels of every gray level is the same. To perform histogram equalization, it is necessary to use an auxiliary function, called the transformation function, T (r). Such transformation function must satisfy two criteria

1. T (r) must be a monotonically increasing function in the interval 0 ≤ r ≤ L − 1.

2. 0 ≤ T (r) ≤ L − 1 for 0 ≤ r ≤ L − 1.

The most usual transformation function is the cumulative distribution function

(cdf) of the original probability mass function, given by

where sk is the new (mapped) gray level for all pixels whose original gray level used to be rk.

Histogram equalization is used for increasing contrast of an image. This can be achieved by using histogram stretching operation.

Implementation of both Techniques in MATLAB:

Following figure shows you MATLAB implementation of Image Negation and Histogram Equalization method
 

Download Respective Published paper on Histogram Equalization and Image Negation:

http://www.2shared.com/document/_QRc4HqD/DH33653657.html 
  
Download Matlab Code for Image Negation and Histogram equalization from following link:

http://www.2shared.com/file/mmRU4HBD/Matlab_code_for_Hist_and_Nega.html

Download Video from following link, it will gives you idea about how to RUN that matlab code:

http://www.2shared.com/video/gXfhBObg/equilization_and_negative_of_i.html

 Video of the above MATLAB Implementation is as follows:

Note: Play only in windows media player...