how to find the pixel value of an image ?

How to find the following

2) pixel within 5 units (out of 255) of pixel ; 3) pixel within 10 units (out of 255) of pixel ; 4) pixel within 25 units (out of 255) of pixel ; 5) pixel within 50 units (out of 255) of pixel .

I used the code a=imread('cameraman.tif');[r c]=size(a). Then accessed each and every row and column values. Is that right.

[Image Analyst]

No, that's not right.

Answer 1

[Image Analyst]

% Specify the pixel value that you want to find intensities around.
targetValue = 173; % Or whatever you want.

% Specify how much intensity around that value do you want to find.
tolerance = 95; % or 10 or 25 or 50 or whatever.

% Get the low and high of that intensity range.
lowValue = uint8(targetValue - tolerance);
highValue = uint8(targetValue + tolerance);

% Get a binary image (like a map) of where are the pixels in range.
pixelsInRange = (grayImage >= lowValue) & (grayImage <= highValue);

[sathish kumar rb]

Where do I read the image in above code?

Is grayImage the image?

[Image Analyst]

grayImage is the image. Usually you get it from reading in some image file with imread():

grayImage = imread(fullFileName);

Please download and run my Image segmentation tutorial: http://www.mathworks.com/matlabcentral/fileexchange/?term=authorid%3A31862&sort=downloads_desc