MATLAB: Scale points on scaled image

image processingimreadimresizeMATLABpolybufferpolyshape

Hello, greetings. I have a little question, see if anyone knows how to solve it.
I have an image I, that to make the test, is going to be the image of cameraman, to which I am going to apply the function imresize and later edge, as you can see:
I = imread('Cameraman.tif');
II = imresize(I,0.25);
figure, subplot(1,2,1);
imshow(I,'InitialMagnification','fit');
J = edge(I);
subplot(1,2,2);
imshow(J,'InitialMagnification','fit');
And now what I do is on the image J define a polygon according to a series of points, for example:
points = [49.5,50.5;143,50.5;143,170.2;49.5,170.3];
figure, imshow(J); hold on; scatter(points(:,1),points(:,2),40,'filled');
And what I need to get is the position of those points but on the original image I. Thank you so much!

Best Answer

The location of points remain the same as you are not using the image II anywhere. All operations are performed on I itself. In image II you are resizing by a factor of 4 (i.e from 256 x 256 to 64 x 64), therefore the location of points if the operations had been performed on II multiply the points by 4 to get locations in original image as in this case its linear downsizing.
Related Question