2 of 2 Corrected spelling, added the parameters used in img transforms from comments to question (I didn't see them for 3 days when in comments)

# Difference between Contrast and Intensity of an Image

I wanted to generate Gray Scale wedge image of 10 Levels in MATLAB and then increase and decrease its Intensity. By high intensity, I mean mapping increasing the level of gray scale intensity in an image from lower value to higher values.

The examples I have tried were performed on a Gray Scale wedge image of 10 levels:

0   28   57   85  113  142  170  198  227  255


I was using the function imadjust. For increasing the intensity levels I used:

 imadjust(grayStepImage, [.35 .75], [0.7 0.8])


The output:

179  179  179  179  184  192  199  204  204  204


and the result in image form:

Similarly, for lowering the intensity I used

imadjust(grayStepImage, [.35 .75], [0.1 0.39])


Original and modified levels are:

0   28   57   85  113  142  170  198  227  255

26   26   26   26   43   64   84   99   99   99


and the result in image form:

Was I actually increasing/lowering intensity of the image? How do those operations relate to the case of increasing and decreasing the contrast of an image?

What I know about contrast is,

Contrast is defined as the separation between the darkest and brightest areas of the image. Increase contrast and you increase the separation between dark and bright, making shadows darker and highlights brighter.

Does that mean, if I want to increase the contrast of an image I should increase the high intensity levels of an image to much higher and lower intensity level to much lower?

I am confused with contrast and the intensity as they seem opposite to each other. Kindly help me out.

 asked Oct 6 '12 at 0:32 Sufiyan Ghori 1,9751111 gold badges2929 silver badges4747 bronze badges