CODEWITHSUNDEEP
matlabmatlab-figurecolorbar
Samo Jerom
Samo Jerom

Reputation: 2371

How to add a 'colorbar' and set 'clim' to a colour image overlaid on a grey level image?

I am trying to overlay a colour image on a grey level image. However, when I try to plot the 'colorbar' and set the 'clim'. Matlab always produce a colorbar according to the underneath grey level image.

However, I want to get the colorbar for the overlaid colour image. Any suggestions would be appreciate. Thanks a lot.

%% Example codes:
  greyImage = imread('AT3_1m4_08.tif');
  colorImage = imread('hestain.png');

  figure,

  greyImagePlot = image(greyImage); colormap(gray); hold on;

  overlayImage = imagesc(colorImage, ...
      'CDataMapping', 'scaled', 'HitTest', 'off');
  alF = 0.5.*ones(size(colorImage, 1), size(colorImage, 2));
  set(overlayImage, 'AlphaData', alF);
  colorbar; % This will show a grey scale colorbar not the colour one I want
  set('CLim', [0 100]); % Also, the colormap limit here is not working

  axis off          
  axis image

Upvotes: 1

Views: 6391

Answers (1)

marsei
marsei

Reputation: 7751

A reference for single figure/multiple colormaps can be found here http://www.mathworks.fr/support/solutions/en/data/1-GNRWEH/index.html

Using images in particular, one can use 'subimage' function.

I also use 'FreezeColor' and 'cbfreeze' functions from 'matlabcentral' when a home-made solution is too tricky. http://www.mathworks.com/matlabcentral/fileexchange/7943-freezecolors-unfreezecolors http://www.mathworks.com/matlabcentral/fileexchange/24371

A straightforward - and lazy - solution for keeping a colorbar across multiple plots within the same axes: first plot the colour image and its colorbar, freeze the colorbar, then plot over the grey level image (no transparency), and finally plot the colour image again (transparency).

Here is a piece of code.

figure;

%first step: RGB image and colorbar
overlayImage = imagesc(colorImage, 'CDataMapping', 'scaled', 'HitTest', 'off');
alF = 0.5.*ones(size(colorImage, 1), size(colorImage, 2));
set(overlayImage, 'AlphaData', alF);
colorbar; 
set(gca, 'CLim', [0 100]); 

cbfreeze; %from 'COLORMAP and COLORBAR utilities' in Matlab Central

%second step: gray image (no transparency)
greyImagePlot = image(greyImage); colormap(gray); hold on;

%third step: plot colour image
overlayImage = imagesc(colorImage, ...
  'CDataMapping', 'scaled', 'HitTest', 'off');
alF = 0.5.*ones(size(colorImage, 1), size(colorImage, 2));
set(overlayImage, 'AlphaData', alF);

axis off          
axis image

Upvotes: 3

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