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how to overlay(superimpose) contour plot(coloured) over a gray scale image

Asked by Srinivas Murthy on 3 May 2011
Latest activity Commented on by Image Analyst
on 26 Nov 2018
I am trying to superimpose a colored contour plot on a grayscale image. I used hold on and then i tried to plot a contour plot. Also i tried using two color maps in a same figure window. But even that is not working. Pls do help me in solving this problem. Typically the contour plot occupies only the central part of the greyscale image , the rest is the greyscale image.

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4 Answers

Answer by Teja Muppirala
on 3 May 2011
Edited by Image Analyst
on 26 Nov 2018
 Accepted Answer

A grayscale image with a colored contour plot superimposed:
% Make some sample grayscale image
I = abs(sin((1:500)'/100)*sin((1:500)/100));
% Convert the grayscale image to RGB
Irgb = cat(3,I,I,I);
% Plot the image and some contours in color
image(Irgb)
hold all
contour(I);
0000 Screenshot.png

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Show 1 older comment
You need to scale the "clim" property of the axes to fit the data from CONTOURF.
Put this line at the end:
set(gca,'clim',[min(displacement_x(:)) max(displacement_x(:))]);
This will all cover up your grayscale image though.
Do you want to make the contour plot transparent? Because that might be not be very simple if you use CONTOURF...
Thanks a lot...I do not want the contour plot to be transparent..By setting up clim, its working as i wanted...

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Answer by Walter Roberson
on 3 May 2011

You haven't indicated what problem you are encountering. Your reference to two color maps hints that you are having getting the two to come out with the colors you want.
Contour plots are a hggroup object that has children that are patch objects. You can change the color properties of the patch objects. The only real trick that have found is that in order to switch between filled and non-filled, you have to change a property in the hggroup object that is the parent of the patch objects.

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Answer by Sean de Wolski
on 3 May 2011

Change the calling function from mesh to contour. Everything else is set up for what you want.

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Answer by safa kassous on 26 Nov 2018

salut ,
j'ai une image a et une image b qui est un contour de a et je veux superposer le contour sur l'image d'origine a.
Quoi faire ?

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Not sure what you're asking, but did you see Teja's answer above?
Or do you mean like where you want to stack the RGB images vertically, like this:
% Takes an RGB image and stacks the separate color channels at different Z levels.
imtool close all; % Close all imtool figures if you have the Image Processing Toolbox.
clc; % Clear the command window.
close all; % Close all figures (except those of imtool.)
clear; % Erase all existing variables. Or clearvars if you want.
workspace; % Make sure the workspace panel is showing.
format long g;
format compact;
fontSize = 20;
rgbImage = imread('peppers.png');
% Extract the individual red, green, and blue color channels.
redChannel = im2double(rgbImage(:, :, 1));
greenChannel = im2double(rgbImage(:, :, 2));
blueChannel = im2double(rgbImage(:, :, 3));
H(1) = slice(repmat(redChannel,[1 1 2]),[],[], 1); %slice() requires at least 2x2x2
set(H(1),'EdgeColor','none') %required so image isn't just an edge
hold on
H(2) = slice(repmat(greenChannel,[1 1 2]),[],[], 2); %slice() requires at least 2x2x2
set(H(2),'EdgeColor','none') %required so image isn't just an edge
H(3) = slice(repmat(blueChannel,[1 1 3]),[],[], 3); %slice() requires at least 2x2x2
set(H(3),'EdgeColor','none') %required so image isn't just an edge
hold off
colormap(gray(256))
axis ij
0000 Screenshot.png

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