How to get onclick coordinate pixel value and location from an image?

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Xylo
Xylo 2014-2-24
编辑： Alberto Zafra Navarro 2024-2-5
Hey frndz, I am new in Matlab. Since 3months ago I am using matlab. Within these 3 months I just learned some matrix manipulation functionm addition, string handling etc. So I need all of your help. Please please help me............... How to get onclick coordinate pixel value and location from an image? Actually I want to get some location(x,y) and corresponding pixel value after clicking on image. how can I do this????????

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采纳的回答

David Young
David Young 2014-2-24
编辑：David Young 2014-2-24
Use ginput
If you want to record multiple points, you can use something like the function that follows. You can easily modify it to display dots rather than lines between the points - check the documentation for the plot function.
function pts = readPoints(image, n)
%readPoints Read manually-defined points from image
% POINTS = READPOINTS(IMAGE) displays the image in the current figure,
% then records the position of each click of button 1 of the mouse in the
% figure, and stops when another button is clicked. The track of points
% is drawn as it goes along. The result is a 2 x NPOINTS matrix; each
% column is [X; Y] for one point.
%
% POINTS = READPOINTS(IMAGE, N) reads up to N points only.
if nargin < 2
n = Inf;
pts = zeros(2, 0);
else
pts = zeros(2, n);
end
imshow(image); % display image
xold = 0;
yold = 0;
k = 0;
hold on; % and keep it there while we plot
while 1
[xi, yi, but] = ginput(1); % get a point
if ~isequal(but, 1) % stop if not button 1
break
end
k = k + 1;
pts(1,k) = xi;
pts(2,k) = yi;
if xold
plot([xold xi], [yold yi], 'go-'); % draw as we go
else
plot(xi, yi, 'go'); % first point on its own
end
if isequal(k, n)
break
end
xold = xi;
yold = yi;
end
hold off;
if k < size(pts,2)
pts = pts(:, 1:k);
end
end
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Kaveh Vejdani
Kaveh Vejdani 2019-7-31
The question remained unanswered. xi and yi are only the coordinates. Where is the pixel value captured?

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更多回答（2 个）

Image Analyst
Image Analyst 2014-2-24
If you don't need the value in your code but just want to interactive view the x,y and RGB as you mouse over the image, you can use impixelinfo().
Alberto Zafra Navarro
编辑：Alberto Zafra Navarro 2024-2-5
According to ChatGPT is easier to do:
function pts = readPoints(image, n)
%readPoints Read manually-defined points from image
% POINTS = READPOINTS(IMAGE, N) reads up to N points only.
imshow(image); % display image
[x,y] = ginput(n);
pts = [x y];
end

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