plz tell me how to choose the colormap for converting a grayscale image to rgb

plz tell me how to choose the colormap for converting a grayscale image to rgb.

[Walter Roberson]

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Answer 1

[Walter Roberson]

Arbitrarily.

IM = rand(64,64);    %a grayscale image
image(IM);
colormap(gray(256));  %display it in gray
pause(5)
colormap(copper(256));  %copper colormap
pause(5)
colormap(hot(256));    %hot colormap

[Gnaneswar Nadh satapathi]

not only three colormaps, there are at about 9 colormaps in MATLAB

[Walter Roberson]

Correct. That was example code. And arbitrary colormaps can be created.

[Walter Roberson]

If you started out with a color image, converted it to grayscale, manipulated that grayscale image, and then want to convert the manipulated image back to the original coloring, then if the manipulation creates any grayscale value that was not already present, then you cannot do the conversion back.

If you converted an image to grayscale, used that grayscale to find a region of interest (ROI), and now want to find the original colors for the pixels within the ROI, then you do not convert the grayscale image back to color: instead you use the ROI to extract pixel values from the RGB image.

Answer 2

[Image Analyst]

You can get a list of predefined colormaps by looking at the colormap function in the help.

someColorMap = winter(256); % Or whatever one you want.
rgbImage = ind2rgb(grayImage, someColorMap);

But you don't need one if you want to create a gray RGB image. Just do:

rgbImage = cat(3, grayImage, grayImage, grayImage);