Convert color to value

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Xin
Xin 2017-11-30
评论： Image Analyst 2017-11-30
Hello everyone. I have a jpg image with blue to red color corresponding to different value. There is also a colorbar showing each colorscale correspond to a value. Is there a simple way to convert this color image into matrix? Thanks a lot.

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采纳的回答

Jos (10584)
Jos (10584) 2017-11-30
So you have combinations of red and blue colour values (R,B) that correspond to a some arbitrary single values V according to the colour scale. Perhaps 2D interpolation, will work for you:
Extract all the the (R,B) combinations for each pixel (Rq,Bq)
Vq = interp2(R,B,V,Rq,Bq)
If the green channel is also important, use interp3.

更多回答（2 个）

Image Analyst
Image Analyst 2017-11-30
See my attached demo where I used the colormap in a thermal image to convert that into a grayscale temperature image.
Stephen23
Stephen23 2017-11-30
Use rgb2ind.
  2 个评论
Jos (10584)
Jos (10584) 2017-11-30
+1 Hopefully it is indeed that simple ...
Image Analyst
Image Analyst 2017-11-30
That's the gist of it, but it's not that simple unless you already have the colormap. In many cases, the user does not and has only some kind of screenshot. My solution also uses rgb2ind() but also does the hard part of figuring out how to obtain the colormap.

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