Intensity Histogram using C++ and OpenCV: Image Processing

Theory

The histogram of a digital image with gray levels in the range [0, L-1] is a discrete function h(r_k) = n_k, where r_k is the kth gray level and n_k is the number of pixels in the image having gray level r_k.

For an 8-bit grayscale image there are 256 different possible intensities, and so the histogram will graphically display 256 numbers showing the distribution of pixels among those grayscale values.

Algorithm

1. Assign zero values to all element of the array h_f;
2. For all pixel (x, y) of the image f, increment h_f [f(x, y)] by 1.