numpy - python: OpenCV depth of image unsupported (CV_64F)

Question

So, I'm trying to show a binary picture with only black and white using this code:

import cv2
import numpy as np

x_img = cv2.imread("lenac.tif")

x_img_g = cv2.cvtColor(x_img, cv2.COLOR_BGR2GRAY)

y = x_img_g > 128

cv2.imshow("", y*1.0)
cv2.waitKey(0)
cv2.destroyAllWindows()

But I'm getting this error:

>Traceback (most recent call last):
File "ex5.py", line 11, in <module>
cv2.imshow("", y*1.0)
cv2.error: OpenCV(4.0.0) c:projectsopencv- 
pythonopencvmodulesimgprocsrccolor.hpp:261: error: (-2:Unspecified 
error) >in function '__cdecl cv::CvtHelper<struct 
cv::Set<1,-1,-1>,struct cv::Set<3,4,-1>,struct 
cv::Set<0,2,5>,2>::CvtHelper(const class cv::_InputArray &,const class 
cv::_OutputArray &,int)'
>Unsupported depth of input image:
>     'VDepth::contains(depth)'
> where
>     'depth' is 6 (CV_64F).

question from:https://stackoverflow.com/questions/65845144/how-to-find-correct-color-values-when-saving-an-imager-via-opencv

Answer 1

try cv2.imshow("", y.astype('float32')) or cv2.imshow("", y.astype('uint8') * 255)

CV_64F means the numpy array 'dtype' is 64bit floating-point opencv only works with 'float32' (32-bit floating point) where image range for imshow is 0.0-1.0 or 'uint8' (unsigned 8-bit) 0-255

Since y was a bool, converting to a number means converting True to 1

for float32, that is fine because 1 is max for imshow range

if you use uint8, that means your trying to display pixels of value 1/255 which will be barely visible, so you can multiply by 255 to bring those pixels to max and appear as bright white pixels