CODEWITHSUNDEEP
pythonopencv
Leo
Leo

Reputation: 1139

Color space conversion with cv2

I'm migrating from cv to cv2 and I'm having difficulties finding an equivalent of the cv.CvtColor function.

I read in the documentation that cv2.cvtColor existed but I don't know how to use the third parameter.

cv2.CV_BGR2Lab doesn't exist. Neither does cv2.CV2_BGR2Lab and when I use cv.CV_BGR2Lab all I get is an error:

cv2.cvtColor(img, img, cv.CV_BGR2Lab)

TypeError: only length-1 arrays can be converted to Python scalars

A simple piece of code that produces the problem:

img = cv2.imread(path)
cv2.cvtColor(img, img, cv.CV_BGR2Lab)

Upvotes: 1

Views: 9509

Answers (2)

martineau
martineau

Reputation: 123403

I think you just have the parameters in the wrong order. The cv2 docs show them in this order: cv2.cvtColor(src, code[, dst[, dstCn]]), which is different from what it was in cv, where the order is: cv.CvtColor(src, dst, code).

So, based on that, along with the information in the other answer regarding color conversion constants name changes, you'd need to use:

cv2.cvtColor(img, cv2.COLOR_BGR2LAB, img)

Upvotes: 6

craastad
craastad

Reputation: 6472

Your looking for this constant

cv.CV_BGR2Lab --> cv2.COLOR_BGR2LAB

And all the other constants for color conversion follow a similar pattern

cv.CV_<CONSTANT> --> cv2.COLOR_<CONSTANT>

I still have not found a good source (even the documentation) for determining how the constants are translated.

Update: See discussions here and here for more about constants.

Upvotes: 5

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