I want to do some image processing with OpenCV (in Python), but I have to start with a PIL Image object, so I can't use the cvLoadImage() call, since that takes a filename. This recipe (adapted from http://opencv.willowgarage.com/wiki/PythonInterface) does not work because cvSetData complains argument 2 of type 'void *' . Any ideas? from opencv.cv import * from PIL import Image pi = Image.open('foo.png') # PIL image ci = cvCreateImage(pi.size, IPL_DEPTH_8U, 1) # OpenCV image data = pi.tostring() cvSetData(ci, data, len(data)) I think the last argument to the cvSetData is wrong too, but I am not sure what it should be.