DistanceTransform gives wrong results (Bug #1531)

Added by pzo - about 13 years ago. Updated about 13 years ago.

Status:Done Start date:
Priority:High Due date:
Assignee:Vadim Pisarevsky % Done:

0%
Category:imgproc, video
Target version:2.4.0
Affected version: Operating System:
Difficulty: HW Platform:
Pull request:

Description

I noticed that distanceTransform from opencv 2.3 yields weird results, e.g the following code:

1arr = numpy.zeros((6, 6), numpy.uint8)
2(distance, labels) = cv2.distanceTransform(arr, cv2.cv.CV_DIST_L1, cv2.cv.CV_DIST_MASK_PRECISE)
3print 'array\n', arr
4print '\ndistance\n', distance

prints:

array
[[0 0 0 0 0 0]
 [0 0 0 0 0 0]
 [0 0 0 0 0 0]
 [0 0 0 0 0 0]
 [0 0 0 0 0 0]
 [0 0 0 0 0 0]]

distance
[[ 2.  1.  1.  1.  1.  2.]
 [ 1.  0.  0.  0.  0.  1.]
 [ 1.  0.  0.  0.  0.  1.]
 [ 1.  0.  0.  0.  0.  1.]
 [ 1.  0.  0.  0.  0.  1.]
 [ 2.  1.  1.  1.  1.  2.]]

So we have weird numbers near the boundary. Other wrong results you can obtain executing the following code:

1arr = numpy.zeros((6, 6), numpy.uint8)
2arr[1:-1,1:-1] = 255
3
4(distance, labels) = cv2.distanceTransform(arr, cv2.cv.CV_DIST_L1, cv2.cv.CV_DIST_MASK_PRECISE)
5distance = distance.astype(numpy.uint8)
6print 'array\n', arr
7print '\ndistance\n', distance

gives:

array
[[  0   0   0   0   0   0]
 [  0 255 255 255 255   0]
 [  0 255 255 255 255   0]
 [  0 255 255 255 255   0]
 [  0 255 255 255 255   0]
 [  0   0   0   0   0   0]]

distance
[[ 8192.  8192.  8192.  8192.  8192.  8192.]
 [ 8192.  8192.  8192.  8192.  8192.  8192.]
 [ 8192.  8192.  8192.  8192.  8192.  8192.]
 [ 8192.  8192.  8192.  8192.  8192.  8192.]
 [ 8192.  8192.  8192.  8192.  8192.  8192.]
 [ 8192.  8192.  8192.  8192.  8192.  8192.]]

Associated revisions

Revision 4f86af7e
Added by Vadim Pisarevsky about 13 years ago

fixed bug #1531. added separate distanceTransformWithLabels function that returns labels, since normally the labels are not needed.

History

#1
Updated by pzo - about 13 years ago

Some update:

I've tested similar code using c++ API and I noticed that I have the same wrong results only when I execute the version of distanceTransform that returns labels as well void distanceTransform(InputArray src, OutputArray dst, OutputArray labels, int distanceType, int maskSize)

The other version w/o labels works fine void distanceTransform(InputArray src, OutputArray dst, OutputArray labels, int distanceType, int maskSize).

It looks like python wrapper always executes the latter buggy one.

#2
Updated by Vadim Pisarevsky about 13 years ago

fixed in r7206

#3
Updated by Vadim Pisarevsky about 13 years ago

  • Status changed from Open to Done
  • (deleted custom field) set to fixed

#4
Updated by Andrey Kamaev about 13 years ago

  • Target version set to 2.4.0
  • Description changed from I noticed that distanceTransform from opencv 2.3 yields weird results, e.g th... to I noticed that @distanceTransform@ from opencv 2.3 yields weird results, e.g ... More

Also available in: Atom PDF