CODEWITHSUNDEEP
matlabmatlab-figure
MJay
MJay

Reputation: 1058

How to overlap color figure on a gray one with colorbar in MATLAB?

I'm trying to color code some parameter values on a gray image in MATLAB. I'm wondering how to show gray image, make parameter values colored on the gray appearance image and on some pixels, and finally draw a colorbar aside the image just showing parameter values range.

Unsuccessful Code since now:

I = Igray; % gray image
Icc = zeros(size(I,1),size(I,2),3); % color coded image
Icc(:,:,1) = I;
Icc(:,:,2) = I;
Icc(:,:,3) = I;
Icc('some address in the image',3) = 'some number between 0 and 255';
imshow(Icc,[])
colorbar % colorbar showing colored parts spectrum

Result image that I need:

enter image description here

Upvotes: 1

Views: 243

Answers (1)

Cris Luengo
Cris Luengo

Reputation: 60444

Try something like this:

I = Igray; % gray image
RGB = [1.0,0.7,0.2]; % color for patch
x = 30:50;
y = 70:90;
% If you gray image is in the range [0,255], make it range [0,1]
I = double(I)/255;
Icc = repmat(I,[1,1,3]);
block = I(y,x);
Icc(y,x,1) = 1 - ((1-block) * (1-RGB(1)));
Icc(y,x,2) = 1 - ((1-block) * (1-RGB(2)));
Icc(y,x,3) = 1 - ((1-block) * (1-RGB(3)));
imshow(Icc)

I'm sure there is a prettier way to encode this, but this way it shows the intent.

You're basically multiplying the grey values with the RGB color you want to make the patch. By inverting the patch and the color first, and inverting the result, the multiplication makes the patch brighter, not darker. That way you get the effect you want where the dark parts show the color also. If you multiply directly without inverting first, black stays black and doesn't show the color.

You'll have to figure out how to coordinate with the color bar after that. There are commands in MATLAB to set the limits of the color bar, you can find those reading the documentation.

The color bar you show uses the PARULA color map. You could do this to find the right RGB value to color your patch:

T; % value to color your patch in, in range [0,1]
cm = parula(256);
RGB = interp1(cm,T*255,'linear')

Upvotes: 1

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