Convert color to value

Question

Xin 2017-11-30

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/370211-convert-color-to-value

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.

0 个评论
显示 -2更早的评论隐藏 -2更早的评论

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

Jos (10584) 2017-11-30

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/370211-convert-color-to-value#answer_293990

在 MATLAB Online 中打开

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.

0 个评论
显示 -2更早的评论隐藏 -2更早的评论

请先登录，再进行评论。

Answer 2

Image Analyst 2017-11-30

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/370211-convert-color-to-value#answer_293994

See my attached demo where I used the colormap in a thermal image to convert that into a grayscale temperature image.

0 个评论
显示 -2更早的评论隐藏 -2更早的评论

请先登录，再进行评论。

Answer 3

Stephen23 2017-11-30

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/370211-convert-color-to-value#answer_293993

Use rgb2ind.

2 个评论
显示无隐藏无

Jos (10584) 2017-11-30

+1 Hopefully it is indeed that simple ...

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.

请先登录，再进行评论。