In this section, we will see how to calculate color histograms. The script that performs this functionality is color_histogram.py. In the case of a multi-channel image (for example, a BGR image), the process of calculating the color histogram involves calculating the histogram in each of the channels. In this case, we have created a function to calculate the histogram from a three-channel image:
def hist_color_img(img):
"""Calculates the histogram from a three-channel image"""
histr = []
histr.append(cv2.calcHist([img], [0], None, [256], [0, 256]))
histr.append(cv2.calcHist([img], [1], None, [256], [0, 256]))
histr.append(cv2.calcHist([img], [2], None, [256], [0, 256]))
return histr
It should be noted that we could have created a for loop or a similar approach in order to call the cv2.calcHist() function three times...
