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Marking where one clicked with ginput

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Guillermo
Guillermo on 25 Jul 2011
Commented: Mohamed Nedal on 13 May 2019
Hi Community,
I was wondering if it were possible to be able to know where one clicked on an image while using ginput(n), i.e. having a red dot over the area where I clicked so that I later am able to remember where it is that I already clicked in case I "zoned out" while clicking.
Thanks in advance.

Accepted Answer

Nathan Greco
Nathan Greco on 25 Jul 2011
I did something similar to this when measuring diameters of soot particles. I would frequently get lost as to where I last clicked, so I decided to create some text where I clicked, stating what was first clicked and what was second clicked.
[x,y] = ginput(1);
h1 = text(x,y,'1', ...
'HorizontalAlignment','center', ...
'Color', [1 0 0], ...
'FontSize',8);
%etc...
%to delete text:
delete(h1);
%etc...
  1 Comment
Melanie Lafanechere
Melanie Lafanechere on 28 Dec 2016
Hello, I have a similar question. Is it possible to populate the coordinates from the ginput with a picture, if so, how? I have a 6x8 grid image and I'm trying to populate the squares with a counter image (.bmp).
Thank you!

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More Answers (3)

Paulo Silva
Paulo Silva on 25 Jul 2011
hold on
[x,y]=ginput(1)
plot(x,y,'r')
  2 Comments
Nathan Greco
Nathan Greco on 25 Jul 2011
h = plot(x,y,'r'); %plots point (or line if x/y are vectors)
delete(h); %deletes plotted items from current plot

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Alice Liu
Alice Liu on 30 Jun 2015
Here's my code for n clicks:
I = imread('yourimage.tif')
figure, imshow(I)
n = 10
coordinates = zeroes(n,2);
hold on
for i=1:n
[x, y] = ginput(1);
coordinates(i,:) = [x, y];
plot(coordinates(:,1), coordinates(:,2), '+');
end
hold off
Hope this helped!
  1 Comment
Mohamed Nedal
Mohamed Nedal on 13 May 2019
Hi, I tried your code with the a FIT file and the function imagesc() as the following:
A = fitsread('R_7.fit');
C = max(A);
f = imagesc(A); colorbar
n = 10;
coordinates = zeros(n,2);
hold on
for i = 1:n
[x, y] = ginput(1);
coordinates(i,:) = [x, y];
plot(coordinates(:,1), coordinates(:,2), 'MarkerSize', 10, '*');
end
hold off
But it gives me this error:
Error using plot
Data must be a single matrix Y or a list of pairs X,Y.
Error in read_interact (line 13)
plot(coordinates(:,1),coordinates(:,2),'MarkerSize',10,'*');
And when I remove the 'MarkerSize' attribute I found that the marker color changes each time I click. How can I keep the marker color without changing and how to increase its size in this case?
Thanks in advance

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Mohamed Nedal
Mohamed Nedal on 13 May 2019
Hi, when I use imagesc() function with plot() function it doesn't display the dots on the image shown by imagesc().
In this case, what's your suggestion?
Please check the attached file and the code here:
A = fitsread('R_7.fit');
C = max(A);
f = imagesc(A); colorbar
hold on
[x,y] = ginput(10);
plot(x,y,'r');

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