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Hi all,
I have an image that looks like this:
From this image, I want to get a list of all of the pixel locations for pixels which are nonzero (white). I'm using OpenCV in Python, and I don't have a good sense of how.
Thanks, Bradley Powers
If you haven't already, I'd suggest looking at NumPy for manipulating your OpenCV images in Python. If you load your images as CvMat objects instead of IplImages then you can manipulate them as NumPy objects without copying the data.
NumPy takes a while to get your head around, but once you do you can use techniques such as the ones given here to achieve what you want.
Based on that, running this program
#! /usr/bin/env python
import cv
import numpy
cvImg = cv.LoadImageM( "testImage.png", # Must use LoadImageM
iscolor=cv.CV_LOAD_IMAGE_GRAYSCALE )
npImg = numpy.asarray( cvImg ) # No copying takes place
coordList = numpy.argwhere( npImg == 255 )
numWhitePoints = len( coordList )
print coordList
print "Found {0} points".format( numWhitePoints )
on your image should output like this
[[ 97 318]
[ 97 322]
[ 97 323]
.. ..
.. ..
[141 200]
[146 189]
[153 178]]
Found 216 points
Looks good. I actually figured this out as well, with slight modification. It turns out that I want these as a list of tuples, so:
def bool_img_to_idx(img):
return zip(numpy.where(array==numpy.asarray(img).max())[0].tolist(),
numpy.where(array==numpy.asarray(img).max())[1].tolist())
My Intro Computer Science prof (who taught me Python) would be rolling over in his grave if he were dead.
Thanks!
Asked: 2011-07-18 04:31:50 -0600
Seen: 5,458 times
Last updated: Jul 18 '11
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