Absolute difference of images: OpenCV vs Numpy
Hey, I’m doing absolute difference between two images and found that the results from opencv and scikit-image are different
im1 = imread(“file1.jpg”) im2 = imread(“file2.jpg”)
cv2.absdiff(im1, im2) np.abs(im1, im2)
I was expecting exactly same result.. could anyone please let me know why I’m observing slightly different results. (I could post images if you’d like) Thanks Surya
I’m sorry, Its
np.abs(im1 - im2)
Surya
On Apr 20, 2017, at 7:10 PM, Surya Kasturi <suryak@udel.edu> wrote:
Hey,
I’m doing absolute difference between two images and found that the results from opencv and scikit-image are different
im1 = imread(“file1.jpg”) im2 = imread(“file2.jpg”)
cv2.absdiff(im1, im2) np.abs(im1, im2)
I was expecting exactly same result.. could anyone please let me know why I’m observing slightly different results.
(I could post images if you’d like)
Thanks Surya
Hi Surya, Yes, test images would be helpful. My intuition without having test data is that you have some underflow errors in the numpy call, which cv2 avoids with some preprocessing: In [1]: im0 = np.array([64], dtype=np.uint8) In [2]: im1 = np.array([65], dtype=np.uint8) In [3]: np.abs(im0 - im1) Out[3]: array([255], dtype=uint8) This is the correct implementation in NumPy: In [6]: np.maximum(im0, im1) - np.minimum(im0, im1) Out[6]: array([1], dtype=uint8) Juan. On 21 Apr 2017, 9:12 AM +1000, Surya Kasturi <suryak@udel.edu>, wrote:
I’m sorry,
Its
np.abs(im1 - im2)
Surya
On Apr 20, 2017, at 7:10 PM, Surya Kasturi <suryak@udel.edu> wrote:
Hey,
I’m doing absolute difference between two images and found that the results from opencv and scikit-image are different
im1 = imread(“file1.jpg”) im2 = imread(“file2.jpg”)
cv2.absdiff(im1, im2) np.abs(im1, im2)
I was expecting exactly same result.. could anyone please let me know why I’m observing slightly different results.
(I could post images if you’d like)
Thanks Surya
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Surya Kasturi