Gray(scale) image with a colormap - how to turn into double?

Hi,

I have an 8-bit image that consists only of gray colors. On checking the characteristics of the image in Matlab with imfinfo, it turns out that it is ColorType "indexed" and has a colormap of 256x3. I would like to transform this image into a simple grayscale image of a n x m matrix (according to its size) class double.

The function ind2gray demands a colormap and using the colormap of this image didn't work on my end. Probably I'm doing something wrong.

Any help is much appreciated.

I'm struggling finding a solution.

Thanks

Answer 1

[David Young]

This works OK:

[imInd, cmap] = imread('10.bmp');
imGrayUint8 = ind2gray(imInd, cmap);
imGrayDouble = im2double(imGrayUint8);
imshow(imGrayDouble);

[John Kau]

Thanks David, that clearly solves it!

Much appreciated!

[Image Analyst]

What did you do when you said "The function ind2gray demands a colormap and using the colormap of this image didn't work on my end"? Because that is exactly what David did. And casting to double shouldn't really be necessary.

[MatlabEnthusiast]

hello. now how do you regain the rgb image from the double image?