Finding a pixel location after imrotate
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Hello all,
I'm trying to find the location of a certain pixel after imrotate with crop. Let's say I have an image I of size = (679, 1024) and then I rotate it with imrotate(I, 10, 'crop') for 10 degrees. So here's the original image and the marked pixel:
And here's the rotate image and the marked pixel after rotation:
So the marked pixel at location (354, 32) is transfomred to the new location (303, 64). How do I find the new location only having the rotation angle (10) and the original location?
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Accepted Answer
Matt J
on 22 Mar 2019
Edited: Matt J
on 22 Mar 2019
Well, the center of the image in your example is at
c=[512.5;340];
and the rotation matrix expressing the rotation is
R=[cosd(10) +sind(10); -sind(10), cosd(10)]
The transformation of ij=[354; 32] is therefore
>> R*(ij-c)+c
ans =
302.9243
64.2024
4 Comments
Matt J
on 22 Mar 2019
Edited: Matt J
on 22 Mar 2019
I have fixed the problem with c, but the center is at c=[512.5, 340] because the first pixel is centered at [1;1], not at [0.5;0.5]. Accordingly, my final result for the coordinate of the rotated point should be right as well,
>> p_new = R*(p-c)+c
p_new =
302.9243
64.2024
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