MATLAB: What is the difference b/w image size 256256 and image size 256256*3

digital image processing

I m doing project with medical images… i have read a .tiff image and calculated size ..it is showing 256*256*3..what is it??

The image that has *3 is an RGB image. The image that does not have *3 is a grayscale image (or a pseudocolor image)

Try this to create a grayscale image:

whiteImage = 255 * ones(N, M, 'uint8');
imshow(whiteImage);

To create an RGB image, try this:

whiteImage = 255 * ones(480, 640, 3, 'uint8');
imshow(whiteImage);

You can convert it into gray image using rgb2gray.

I1 = rgb2gray(I) ;   % where I is RGB image