Add transparency to colormap

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Oliver Lestrange
Oliver Lestrange 2020-8-11
评论： Image Analyst 2020-8-16
Hi,
How can I add transparency to a colormap 2D?
I have the following code and I am using the version R2016a of MATLAB.
function covFunc( mapa, minPrx, maxPrx, arrayPrx )
wallMask(:,:,1) = mapa.img(:,:,1) ~= 255 & mapa.img(:,:,2) ~= 255 & mapa.img(:,:,3) ~= 255;
cover = (arrayPrx') .* ~wallMask + wallMask.*minPrx;
cover = cover + 0 * wallMask;
cover = (arrayPrx') .* wallMask;
imshow(cover);
caxis([minPrx maxPrx]) % Set colormap limits
colormap (jet(round((maxPrx-minPrx/50))))
colorbar
end
I need that the image stays intact and the new colors created by the color map stay transparent.

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回答（1 个）

Image Analyst
Image Analyst 2020-8-11
编辑：Image Analyst 2020-8-11
I'd probably create a new RGB image with the colormap and ind2rgb(). Then take a weighted average of them
rgbImage = cat(3, grayImage, grayImage, grayImage);
rgbOverlay = ind2rgb(grayImage, cmap);
factor = 0.6; % 60% or whatever.
rbgOutput = uint8(factor * double(rgbImage) + (1-factor) * 255 * rg0bOverlay);
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Oliver Lestrange
Oliver Lestrange 2020-8-11
编辑：Oliver Lestrange 2020-8-16
In my code the ind2rgb returns error.
Assignment has more non-singleton rhs dimensions than non-singleton subscripts
Error in ind2rgb (line 34)
rout(:,:,1) = r;
I am using:
cmap = jet((round((maxPrx-minPrx/50))));
rgbOverlay = ind2rgb(mapa.img, cmap)
Where mapa.img is the image.
I don't understand very well image processing... but cmap is getting a 14x3 matrix and the image is a 15x15x3. I don't know if that can be a problem...
But I think the matter here is that the values of maxPrx and minPrx are negative.
Any suggestion?
Thanks for the demonstration above.
Image Analyst
Image Analyst 2020-8-16
You forgot to attach your script and your image. So, how can I help? cmap can be as many colors as you want to quantize it into. I have no idea what your maxPrx and minPrx are.

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