Convert to RGB file with colormap defined with different clim

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Fiona Gong 2020-9-26

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https://ww2.mathworks.cn/matlabcentral/answers/600478-convert-to-rgb-file-with-colormap-defined-with-different-clim

评论： Fiona Gong 2020-9-27

Hi

I have a greyscale image 256x256 with background NaNs and all values are between [0 1]. I then use imshow to display the image, set Clim to different ranges [-0.1,1] or [-0.1 0.5] etc. Putting -1 in the clim range helps to set background NaNs to white. I then define colormap mannually with different clim ranges and save the cmap.

Once colormap and clim is finalised I then tried to save to rgb image using ind2rgb:

rgbImage = ind2rgb(greyImage, cmap);

imshow(rgbImage);

It gives me a different image and I think it's to do with Clim. Is there any way I can save greyscale image to rgb image using clim range and colormap I definied?

Many thanks!

Fiona

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Answer 1

Walter Roberson 2020-9-26

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https://ww2.mathworks.cn/matlabcentral/answers/600478-convert-to-rgb-file-with-colormap-defined-with-different-clim#answer_501040

There is a File Exchange contribution named freezeColors https://www.mathworks.com/matlabcentral/fileexchange/7943-freezecolors-unfreezecolors that takes a currently displayed colormap image and takes into account the active colormap and active clim, and converts the image into an RGB image. You can then fetch the CData property from the image handle.