CODEWITHSUNDEEP
pythonopencvmatplotlib
Abhay Doke
Abhay Doke

Reputation: 61

imshow() and matplotlib() are not working together

I have this simple OpenCV code to plot histogram of an Image.

from PIL import Image
from numpy import *
from pylab import *
import cv2

image=cv2.imread('/media/755784/New Volume/DATA/Images/opencv.jpg')

h,w=image.shape[:2]

cv2.imwrite('/media/755784/New Volume/DATA/Images/result.png',image)
print h,w

cv2.imshow("Image",image)
cv2.waitKey(0)## <--

print 'Plotting histogram'
hist=cv2.calcHist(image,[0],None,[256],[0,256])
plt.hist(image.ravel(),256,[0,256])
plt.show()
while True:
    k=cv2.waitKey(30)
    if k==27:
        break
cv2.destroyAllWindows()

When I remove the waitKey(0) after the imshow(), the histogram gets plotted first and unless you close the plot, the image is not displayed. Is this a particular problem with python or matplotlib?

Upvotes: 2

Views: 3807

Answers (1)

hitzg
hitzg

Reputation: 12711

Your plt.show() blocks the code, so you don't get to the while loop.

But you can plot the image also with matplotlib. That makes it easier:

import matplotlib.pyplot as plt
import cv2

image=cv2.imread('/tmp/stinkbug.png')

fig = plt.figure(figsize=(10,3))
ax1 = plt.subplot(1,2,1)
ax1.imshow(image)
ax2 = plt.subplot(1,2,2)
ax2.hist(image.ravel(),256,[0,256])
plt.show()

(Note: I used a different image)

Upvotes: 3

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