convert openCV image into PIL Image in Python (for use with Zbar library)

Question

I\'m trying to use the Zbar library\'s QR code detection methods on images I extract with OpenCV\'s camera methods. Normally the QR code detection methods work with images (jpg,

Answer 1

Are you trying to obtain a RGB image? If that is the case, you need to change your parameters from this:

cv_im = cv.CreateImage((320,200), cv.IPL_DEPTH_8U, 1)
pi = Image.fromstring("L", cv.GetSize(cv_im), cv_im.tostring())

to that:

cv_im = cv.CreateImage((320,200), cv.IPL_DEPTH_8U, 3)
pi = Image.fromstring("RGB", cv.GetSize(cv_im), cv_im.tostring())

since it is documented almost nowhere, but the 'L' parameter of Image.fromstring is for 8-bit B&W images. Besides, you need to change the argument of your cv.CreateImage function from 1 (single channel image) to 3 (3 channels=RGB).

Hope it works for you. Cheers

Answer 2

With the python CV2, you can also do this:

import Image, cv2

cap = cv2.VideoCapture(0) # says we capture an image from a webcam
_,cv2_im = cap.read()
cv2_im = cv2.cvtColor(cv2_im,cv2.COLOR_BGR2RGB)
pil_im = Image.fromarray(cv2_im)
pil_im.show()

Answer 3

A simple way is to directly swap the channels. Suppose you are trying to convert a 3-channel image file between OpenCV format and PIL format. You can just use:

img[...,[0,2]]=img[...,[2,0]]

In this way, you won't be bothered with cv2.cvtColor as this function only works on images with certain depth.

Answer 4

I think I may have found the answer. I'll edit later with results.

OpenCV to PIL Image

import Image, cv
cv_im = cv.CreateImage((320,200), cv.IPL_DEPTH_8U, 1)
pi = Image.fromstring("L", cv.GetSize(cv_im), cv_im.tostring())

Source: http://opencv.willowgarage.com/documentation/python/cookbook.html