image processing

What is the relationship between gray level of an image to histogram. I know about histogram that implies the number of pixels in particular gray level.But is it possible to calculate gray percentage using histogram value?.....

Answer 1

[Amith Kamath]

Histogram is a statistic of the image that gives information about the number of pixels of a particular intensity. It is irreversible, in the sense that with a histogram, you cannot recreate the image, and hence cannot predict the pixel value at a particular point. Having said this, it is possible to calculate the percentage of a particular gray level. This is equivalent to just normalizing the histogram on a unit scale. For example,

I = imread('rice.png');

hist = imhist(I);

%percentage of pixels that have the value 105, is

hist(105)/sum(hist) %This is the fraction.

and as a check, sum(hist) should always be equal to the number of pixels in the image.

Hope this helps!