Scale points on scaled image

Question

Alejandro Fernández 2020-7-15

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/565247-scale-points-on-scaled-image

评论： Alejandro Fernández 2020-7-22

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!

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Answer 1

Dinesh Yadav 2020-7-21

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https://ww2.mathworks.cn/matlabcentral/answers/565247-scale-points-on-scaled-image#answer_468651

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.