Using colormap of a lookup table from MetaMorph in MATLAB?

There is a Look up table from the image analysis software MetaMorph I want to import and use in MATLAB as a 256X3 colormap. I was trying to see if I can 1) import LUT files (.lut extension) directly to MATLAB or 2) extract the colormap from a colored image. Has anyone had experience of doing this? I am aware of the function of rgb2ind, which can return [indexed_image, colormap], with a colormap that can map the indexed_image to the colored image. However is there a way I can do it for any other grayscale image I want to apply the colormap to? Please let me know if you have any suggestions. Thanks.

Answer 1

[Abhinaya Kennedy]

Hi Guangfeng Yu,

MATLAB doesn't directly import .lut files, but you can achieve your goal in a couple of ways:

1. Reading the LUT as text and converting to colormap:

• MetaMorph LUT files might be plain text files with RGB values for each index.
• Use "fopen" to open the file and "fscanf" to read the RGB values into a matrix.
• The matrix should have dimensions (256, 3) with each row representing an RGB value for a corresponding index (0-255). This matrix can be directly used as your colormap.

2. Extract from reference image:

• Read the image with "imread".
• Use "rgb2ind" to get a 256-color indexed image and its colormap (LUT).

3.Applying the colormap:

• Use "imshow" with your grayscale image and the obtained colormap as the third argument.

Here are some resources that might be helpful:

• fopen: https://www.mathworks.com/help/matlab/ref/fopen.html
• fscanf: https://www.mathworks.com/help/matlab/ref/fscanf.html
• rgb2ind: https://www.mathworks.com/help/matlab/ref/rgb2ind.html
• imshow: https://www.mathworks.com/help/matlab/ref/imshow.html