OpenCV: Can't process TOP data as CV_8UC1

Beginners
1

I am having trouble getting some OpenCV functions to behave as they should. The example on the wiki uses goodFeaturesToTrack and works for me, but when I use OpenCV code that works fine outside of TouchDesigner, I have trouble ingesting the TOP.

In my onCook:

...
 topRef = scriptOp.par.Top.eval()
 img = topRef.numpyArray()
 img = img[:,:,:3]
 # the cvtColor on the next line SHOULD make the previous one unnecessary,
 # but I want to show that I've tried both approaches.
 img = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)
 thresh = cv2.adaptiveThreshold(img, 255, 1, 1, 55, 2)
...

Excuting that last line results in the following error:

cv2.error: OpenCV(4.0.0)
C:\projects\opencv-python\opencv\modules\imgproc\src\thresh.cpp:1507:
error: (-215:Assertion failed)
src.type() == CV_8UC1 in function 'cv::adaptiveThreshold'

The only workaround I’ve found is using OpenCV’s imread and imwrite to save and reopen img. This is, of course, impossibly slow.

2

Hey dahud,

this is because opencv expects images to be in 8bit.
Also opencv works in colors in 0-255 range, instead of 0-1 as TD does.
So replace this line:

img = topRef.numpyArray()

for

img = topRef.numpyArray()*255
img = img.astype(np.uint8)
3

Thank you! I managed to get to the bottom of this myself late last night.
For the record, here’s my full input processing routine:

        img = op("camMono").numpyArray()
        img = img[:,:,:3]

        img *= 255
        img = np.uint8(img)
        img = cv2.cvtColor(img, cv2.COLOR_BGRA2GRAY)
4

This should be in the docs…