How to change the color of a 16bit image from Grays to a color mode?

Hi

I have an image which is 16bit. It is grays. I wonder how can I change it to a specific color, e.g, Yellow? I tried to convert it to RGB first, but somehow [I,map]=imread(16bitimage) doesn't give the colormap.

Thanks a lot

Answer 1

[Shirley]

I found that this works for me. Suggestions are more than welcome. Thanks

1)self define a colormap, e.g

%Yellow [1 1 0]
   YellowColormap=zeros(256,3);
    for i=1:256
        YellowColormap(i,1) = (i-1)/256;
        YellowColormap(i,2) = (i-1)/256;
    end

2)X=imread(16bit image);

    imshow(X,'DisplayRange',[0 65535],'Colormap',YellowColorMap)

[Image Analyst]

Or, vectorized:

YellowColormap = gray(256);
YellowColormap(:,3) = 0;

[Shirley]

That is clever! I didn't know this function before. Thanks a lot!

Answer 2

[Walter Roberson]

image_as_rgb = repmat(image_as_gray, [1 1 3]);

Now you can manipulate image_as_rgb .

Or you might prefer to use ind2rgb() -- though to do that you need to define a colormap that has as many entries as max(image_as_gray)+1, which for a 16 bit image could be as many as 65536 entries.

[Shirley]

Hi Walter

Thank you very much for the reply. But what is the next after getting image_As_rgb?

It seems that I still need to self define my own Yellow color map, and then perform

imshow(image_as_gray,'DisplayRange',[0 65535],'Colormap',YFPColorMap)?

This worked out for me as well

[Walter Roberson]

yellow_image = cat(3, repmat(image_as_gray, [1 1 2]), zeros(size(image_as_gray)));
imshow(yellow_image);

[Shirley]

Somehow neither image_as_gray and yellow_image didn't show. It was completely black.Any clue?

[Walter Roberson]

yellow_image = cat(3, repmat(mat2gray(image_as_gray), [1 1 2]), zeros(size(image_as_gray)));
imshow(yellow_image)

You have a uint16 image, but your data range is only a small fraction of uint16.

[Shirley]

Thanks! It works now after I adjusted the image