Add transparency to colormap

Question

Oliver Lestrange 2020-8-11

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/578224-add-transparency-to-colormap

评论： Image Analyst 2020-8-16

在 MATLAB Online 中打开

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.

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

Image Analyst 2020-8-11

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/578224-add-transparency-to-colormap#answer_478216

编辑：Image Analyst 2020-8-11

在 MATLAB Online 中打开

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);

4 个评论
显示 2更早的评论隐藏 2更早的评论

Oliver Lestrange 2020-8-11

编辑：Oliver Lestrange 2020-8-16

在 MATLAB Online 中打开

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 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.

请先登录，再进行评论。