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Two colormaps in the same plot

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Hi,
I am superimposing two images, here, I would like to use different colormap for first and second images. For e.g. jet for image 1 and hot for image 2..
I have tried this, however, at the end, both the images got the colromap defined for image 2. If somebody has gone through this kind of situtaion, please help me with this..

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Accepted Answer

Steve Eddins
Steve Eddins on 10 Nov 2020
The ColorBar object has an undocumented Colormap property. You can set this property directly to control the colors displayed by the ColorBar. You can use the documented properties such as Limits so that the display corresponds to your original data values.
Just be aware that the ColorBar's behavior with the respect to the Colormap property might change in a future release.
And don't tell anyone that I told you about this. ;-)

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Turbulence Analysis
Turbulence Analysis on 30 Nov 2020
Steeve,
I did defined individually the color pattern and position as shown below. I am able to get the two colorbars in the defined position i.e. east and west, but not the pattern...
%%% First image
colormap(ax1,'jet');
c = colorbar(ax1,'Position',[.88 .11 .0275 .815],'Location', 'east','FontSize',20,'TickLabelInterpreter', 'latex');
%%% Second image
colormap(ax2,'hot')
c1 = colorbar(ax2,'Position',[.88 .11 .0275 .815],'Location', 'west','FontSize',20,'TickLabelInterpreter', 'latex');
Steve Eddins
Steve Eddins on 1 Dec 2020
I see now that it looks like your code is trying to create two different axes objects (ax1 and ax2), but it really only makes 1. The function gca returns the current axes, or it makes one if one does not already exist. So, this line:
ax2=gca;
does not make a second axes. It just returns the first. Because of that, you are not setting the colormaps of two different axes objects; rather, you are just overwriting the colormap of one.
I don't think you'll be able to get this transparent overlay idea to work in two different axes. My best suggestion is still to work in one axes and set the Colormap property of each colorbar directly, as in:
c1.Colormap = jet(256);
c2.Colormap = hot(256);
Turbulence Analysis
Turbulence Analysis on 1 Dec 2020
Great, Thanls a lot steve..
Now, I am getting two color bars

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More Answers (1)

Steve Eddins
Steve Eddins on 9 Nov 2020
You can't display images with two different colormaps within the same axes. As a workaround, you could convert both images from indexed to rgb, like this:
rgb1 = ind2rgb(X1,jet(256));
rgb2 = ind2rgb(X2,hot(256));
These two images can then be displayed or superimposed together. RGB image display is independent from the colormap.

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Turbulence Analysis
Turbulence Analysis on 9 Nov 2020
Because I have to intrept something based on the image displayed with real intensity values...
Steve Eddins
Steve Eddins on 9 Nov 2020
Can you expand a little bit more in your replies? I don't think I'm getting enough information to be able suggest a workaround. Please say more about exactly what you are doing or displaying with the images so that it makes a difference what the CData values are.
Turbulence Analysis
Turbulence Analysis on 10 Nov 2020
I have attached the superimposed images plotted from real values (Capture2) and RGB values (Capture1). As you see from the images, the colormap of capture 2 clealry depicts the reals values (0 to 4000), however, the colormap of RGB shows the intensity values from 0 to 1.
Anyways, RGB image can be dipslayed independent of colormap, hence, I can display the colormap with real values, so this problem is solved.
Since, I have displayed the images using two color patterns i.e. jet, hot (see Capture 1), here, could you please tell me how to include the two color bars ???
%%%%%%%%%%% Image display with RGB values %%%%%%%%%%%% (Capture1)
I=readimx('B00003.im7');
h = (I.Frames{1}.Components{1}.Planes {1,1})';
h1 = fix(h/10);
h1(h1==0) = 1 ;
rgb1 = ind2rgb(h1,jet(256));
ax1=gca;
G = imagesc(flipud(rgb1));
c = colorbar('FontSize',20,'TickLabelInterpreter', 'latex');
G.AlphaData = 0.5;
set(gca, 'YDir','normal')
axis equal
hold on;
I1=readimx('B00045.im7');
h2 = (I1.Frames{2,1}.Components{1,1}.Planes {1,1})';
h3 =fix(h2/10);
h3(h3==0) = 1 ;
rgb2 = ind2rgb(h3,hot(256));
ax1=gca;
GH = imagesc(flipud(rgb2));
c1 = colorbar('FontSize',20,'TickLabelInterpreter', 'latex');
GH.AlphaData = 0.5;
set(gca, 'YDir','normal')
axis equal
%%%%%%%%%%% Image display with real values %%%%%%%%%%%% (Capture2)
I=readimx('B00003.im7');
h = (I.Frames{1}.Components{1}.Planes {1,1})';
ax1=gca;
colormap(hot);
G = imagesc(flipud(h));
c = colorbar('FontSize',20,'TickLabelInterpreter', 'latex');
set(gca, 'YDir','normal')
axis equal
hold on;
I1=readimx('B00045.im7');
h2 = (I1.Frames{2,1}.Components{1,1}.Planes {1,1})';
ax1=gca;
colormap(jet);
GH = imagesc(flipud(h2));
c1 = colorbar('FontSize',20,'TickLabelInterpreter', 'latex');
GH.AlphaData = 0.7;
set(gca, 'YDir','normal')
axis equal

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