Convert uint8 image to doubles

Hello,

I'm trying to convert a png image from the web to a single 2d array of doubles, scaled from 0 to 1.

im2double works. But the problem is the image is actually 3 2d arrays. The first corresponds to red intensities, second one to green intensities, and third one is blue intensities (this seems to be a common format). im2double converts each of the three 2d arrays, but I need to combine them into a single 2d array for black/white intensity.

Is there a function for this? Any help?

Answer 1

[Walter Roberson]

im2double() applied to the 3D ("truecolor") array would convert the entire array.

If the original image is grayscale that has been represented as RGB, then the three color planes would be equal to each other. You would not need to convert each of the planes individually to get out a grayscale image represented in RGB

repmat( im2double(PNGImage(:,:,1)), 1, 1, 3);  %convert one plane, clone that

If for some reason you do have three separate arrays, say R, G, B, then

cat(3, im2double(R), im2double(G), im2double(B))

or equivalently

im2double( cat(3, R, G, B))

[Jacob]

Thanks for the tips!

I found what I was looking for - to convert a 3D RGB array, matlab has rgb2double() which takes an RGB array with values from 0 - 255 and returns a single 2D array with double values from 0 - 1.