Cv::imshow() on a 32FC1 image

https://docs.opencv.org/4.x/d7/dfc/group__highgui.html#ga453d42fe4cb60e5723281a89973ee563

If the image is 32-bit or 64-bit floating-point, the pixel values are multiplied by 255. That is, the value range [0,1] is mapped to [0,255].