Opencv: save a double matrix with imwrite

Question

I have a matrix (Mat) constituted by double, in the range [0,1]. When I save it by means of command imwrite, the resulting image is totally black. I suppose the problem is a casting problem, but I don't know how to solve it. Thanks

Answer 1

The only way for OpenCV to store array of doubles without converting them to other formats (and losing information) is by using FileStorage . imwrite is restricted to arrays of 'char' or 'short'.

Answer 2

You get the totally black image is because all images pixels are within range [0,1] (actually either 0 or 1 when saving to image), which is approaching total black (either for gray-scale image or color image).

To save the matrix to the image with normal color, you need first to transform the double matrix to range [0, 255] by multiplying each value by 255 . Remember to transform back if you later load the matrix from this image by dividing each value by 255 .