IPhistogram.m:

function [output] = IPhistogram(inputImage)
output = zeros(256,1);
for x = 1:size(inputImage, 1)
    for y = 1:size(inputImage, 2)
        output(inputImage(x,y) + 1) = output(inputImage(x,y) + 1) + 1;
    end
end



IPhisteq.m:

function [output] = IPhisteq(inputImage)
histogram = IPhistogram(inputImage);
cumHist = zeros(1, 256);
for i=0:255
    cumHist(i + 1) = size(find(inputImage <= i), 1);
end
cumHist = cumHist / prod(size(inputImage));
output = uint8(cumHist(inputImage + 1) * 255);