Colormap, how to get the color of the sea

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Xin 2016-12-1

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https://ww2.mathworks.cn/matlabcentral/answers/314829-colormap-how-to-get-the-color-of-the-sea

编辑： DGM 2023-1-3

This is an interesting question to me. I wanted to create a nice colormap with very smooth and gradual transition from white to sea blue. I tried to do it manually in colormap but it does not work out very well. Anybody who has explored this, or know some developed colormap?

Many thanks

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Answer 1

Image Analyst 2016-12-1

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https://ww2.mathworks.cn/matlabcentral/answers/314829-colormap-how-to-get-the-color-of-the-sea#answer_245429

在 MATLAB Online 中打开

Try a program where you can easily get the RGB values of some color of blue that you like, like (r,g,b) = (rBlue, gBlue, bBlue). Then use linspace().

numColors = 256; % Good value for 24/32 bit displays.
oceanRed = 15;
oceanGreen = 127;
oceanBlue = 230;
myColorMap = [linspace(oceanRed, 255, numColors)'/255,...
  linspace(oceanGreen, 255, numColors)'/255,...
  linspace(oceanBlue, 255, numColors)'/255]
imshow('cameraman.tif');
colormap(gca, myColorMap);
colorbar

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noor 2023-1-3

what does the function numColors do?

DGM 2023-1-3

编辑：DGM 2023-1-3

在 MATLAB Online 中打开

The variable numColors specifies the number of tuples (rows) in the colormap. It's easy enough to test.

numColors = 5; % change the value and see what happens
oceanRed = 15;
oceanGreen = 127;
oceanBlue = 230;
myColorMap = [linspace(oceanRed, 255, numColors)'/255,...
    linspace(oceanGreen, 255, numColors)'/255,...
    linspace(oceanBlue, 255, numColors)'/255]
myColorMap = 5×3
    0.0588    0.4980    0.9020
    0.2941    0.6235    0.9265
    0.5294    0.7490    0.9510
    0.7647    0.8745    0.9755
    1.0000    1.0000    1.0000