• Asking for Help
• How do I detect the circles
• round shapes in a color image?

Hello everybody!

I just installed the python-opencv package on Ubuntu 10.10 and I was wondering how I can use it to detect the circles/round figures in an RGB image. I am not an expert in images and I do not know what terms like HSV and 8-bit image mean(I know these two now, of course).

I tried this code, which I adapted from a website, and it doesn't work:

   1 import cv
   2         
   3 def main():
   4         
   5         storage = cv.CreateMemStorage(0)
   6         
   7         im = cv.LoadImageM("Proba1.jpg")
   8         size = (640, 480)
   9         hsv_im = cv.CreateImage(size, cv.IPL_DEPTH_8U, 3)
  10         thresholded = cv.CreateImage(size, cv.IPL_DEPTH_8U, 1)
  11         thresholded2 = cv.CreateImage(size, cv.IPL_DEPTH_8U, 1)
  12          
  13         hsv_min = cv.Scalar(0, 50, 170, 0)
  14         hsv_max = cv.Scalar(10, 180, 256, 0)
  15         hsv_min2 = cv.Scalar(170, 50, 170, 0)
  16         hsv_max2 = cv.Scalar(256, 180, 256, 0)
  17         
  18         cv.CvtColor(im, hsv_im, cv.CV_BGR2HSV)
  19         cv.InRangeS(im, hsv_min, hsv_max, thresholded)
  20         cv.InRangeS(im, hsv_min2, hsv_max2, thresholded2)
  21         cv.cvOr(thresholded, thresholded2, thresholded)
  22         # pre-smoothing improves Hough detector
  23         cv.Smooth(im, im, cv.CV_GAUSSIAN, 9, 9)
  24         
  25         
  26         circles = cv.HoughCircles(im, im, cv.CV_HOUGH_GRADIENT, 2, thresholded.height/4, 100, 40, 20, 200)
  27         
  28         
  29 if __name__ == '__main__':
  30         main()

The error I get is: OpenCV Error: Sizes of input arguments do not match () in cvCvtColor, file /build/buildd/opencv-2.1.0/src/cv/cvcolor.cpp, line 2208OpenCV Error: Sizes of input arguments do not match () in cvCvtColor, file /build/buildd/opencv-2.1.0/src/cv/cvcolor.cpp, line 2208

I really do NOT understand the whole code above(not the error, the code) since there is no good documentation about opencv and python available. I also tried installing pyopencv but it didn't work.

I would be very glad if someone could show me a code sample that takes a .jpg image, makes it 8-bit(because this is another error it gives me) and detects the circles in it. It would also be nice if you could tell me a good opencv tutorial for python.

Thanks for your time and interest and sorry for my grammar.

Calin

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