17multi-dimensional_hist_2D.py

from matplotlib import pyplot as plt
import numpy as np
import argparse
import cv2

ap = argparse.ArgumentParser()
ap.add_argument("-i", "--image", required=True, help="Path to the image")
args = vars(ap.parse_args())

image = cv2.imread(args["image"])
cv2.imshow("Original", image)

chans = cv2.split(image)
colors = ("b", "g", "r")

fig = plt.figure()
plt.xlabel("Bins")
plt.ylabel("# of Pixels")

ax = fig.add_subplot(131)
hist = cv2.calcHist([chans[1], chans[0]], [0, 1], None, [32, 32], [0, 256, 0, 256])
p = ax.imshow(hist, interpolation="nearest")
ax.set_title("2D Color Histogram for G and B")
plt.colorbar(p, ticks=np.arange(0, 1200+1, 150))

ax = fig.add_subplot(132)
hist = cv2.calcHist([chans[1], chans[2]], [0, 1], None, [32, 32], [0, 256, 0, 256])
p = ax.imshow(hist, interpolation="nearest")
ax.set_title("2D Color Histogram for G and R")
plt.colorbar(p, ticks=np.arange(0, 1200+1, 150))

ax = fig.add_subplot(133)
hist = cv2.calcHist([chans[0], chans[2]], [0, 1], None, [32, 32], [0, 256, 0, 256])
p = ax.imshow(hist, interpolation="nearest")
ax.set_title("2D Color Histogram for B and R")
plt.colorbar(p, ticks=np.arange(0, 1200+1, 150))

print "2D histogram shape: %s, with %d values" % (hist.shape, hist.flatten().shape[0])

plt.show()
cv2.waitKey(0)