Can't show the image with white text, opencv

Question

The original image is

font                   = cv2.FONT_HERSHEY_SIMPLEX
bottomLeftCornerOfText = (10,150)
fontScale              = 1
fontColor              = (255,255,255)

cv2.putText(img=img,text='Hello World!', 
    org = bottomLeftCornerOfText,
    fontFace=font, 
    fontScale=fontScale,
    color=fontColor,
    lineType=cv2.LINE_AA,
    thickness=1)

After running the code above, I got image like this

Only text showed and the background image disappeared. I also tried other colors like blue and green, they all worked fine, both image and text were kept. I wonder why white text doesn't work here and how can I fix it.

Answer 1

Is the image type float from 0.0 to 1.0? Is it one channel grayscale? You are assigning text color with 3 channels and 255 valued... Probably you're having trouble because of one of those.