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Thread Subject:
interpolation for rotated images

Subject: interpolation for rotated images

From: PANDIAN` NITHYANANDAM

Date: 27 Nov, 2011 18:00:10

Message: 1 of 3

hai friends

i am rotating an image. during that process
can you say that interpolation will be applied to an image for all the degrees which is rotated 1-360 degree except 90,180 and 270.

It is immatter of the type of rotation (nearest neighbor, bilinear, bicubic).

help is appreciated

Subject: interpolation for rotated images

From: Bruno Luong

Date: 27 Nov, 2011 18:12:08

Message: 2 of 3

"PANDIAN` NITHYANANDAM" <nithyanandamp@ssn.edulin> wrote in message <jattr9$u5$1@newscl01ah.mathworks.com>...
> hai friends
>
> i am rotating an image. during that process
> can you say that interpolation will be applied to an image for all the degrees which is rotated 1-360 degree except 90,180 and 270.

Interpolation _always_ occurs when the image is rotated. Just by chance at 90-degree-fold angle, the pixels before and after rotation fall on top of each other.

Bruno

Subject: interpolation for rotated images

From: Matt J

Date: 27 Nov, 2011 19:26:08

Message: 3 of 3

"PANDIAN` NITHYANANDAM" <nithyanandamp@ssn.edulin> wrote in message <jattr9$u5$1@newscl01ah.mathworks.com>...
> hai friends
>
> i am rotating an image. during that process
> can you say that interpolation will be applied to an image for all the degrees which is rotated 1-360 degree except 90,180 and 270.
==================

You can say that, but it has no significance. If you look inside IMROTATE, you will see that it is smart enough to detect whether the rotation angle is a multiple of 90 degrees and if so it skips the interpolation in favor of a faster processing method.

It's important to understand, though, that this does not affect the result, only the speed of the computation. If IMROTATE did execute interpolation at 90/180/270, it would get the same result (within numerical precision).

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