how can i plot a histogram of pixel values?

i'm working on a simulation and it contains a histogram of pixel differences for original image and marked one. but i do not understand this plot (that comes in attachment). can anybody please review it and guide me on that?

[Wayne King]

Did you attach anything?

[sanaz]

i had but seems like it was not attached, i did again, can you see it now?

Answer 1

[Image Analyst]

Your plot shows that there is a pixel-to-pixel difference (same location) of anywhere from -4 to +0.5 gray levels.

diffImage = double(image1) - double(image2);
minValue = min(diffImage(:));
maxValue = max(diffImage(:));
edges = linspace(minValue, maxValue, 500); % 500 bins
counts = histc(diffImage(:));
plot(edges, counts, 'b-');
grid on;

[sanaz]

thank you, i've tried it and i get an error for histc. should i correct it or something?

[Image Analyst]

Yes.

[sanaz]

i corrected it and got the right answer. thank you very much.