Given an image I of four pixels:
I = [[0, 0], [1, 0],
[0, 1], [1, 1]]
Translate so that origin is at the centre of the image (subtract -1 from x and y):
I = [[-1, -1], [0, -1],
[-1, 0], [0, 0]]
Rotate the image by 90 degrees:
I = [[-1, 1], [-1, 0],
[0, 1], [0, 0]]
Translate back (by adding back 1):
I = [[0, 2], [0, 1],
[1, 2], [1, 1]]
Note that all Y points are shifted up by 1. The image should instead be:
I = [[0, 1], [0, 0],
[1, 1], [1, 0]]
Is there a reason this is happening? I am unable to rotate images about their centre without incuring this shift in the y direction. Is it something wrong with the translations? I've spent considerable time on this, and I am unsure of what I am doing wrong.
Edit it appears the amount I was translating by was incorrect, it should be 0.5:
