Need help on Image rotation.

matthieu.darbois
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July 3, 2009 1:12 AM PDT
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#1
Quoting - mahantesh
Hi,

When we rotate image by 90 degree using ippiRotate_8u_C4R() , for MxN resolutions the output is MxN image with 2 black strips at the sides of the image. Is it possible to get rid of these black strips? Is it possible to change the size of the image to NXM ? or Is it possible to change the size of the image to MxM ?

We are trying to remove these black strips by the calling the function ippiRotate_8u_C4R() and then ippiResizeShift_8u_C4R(), this does the trick but image get stretched and there is peformance hit in our application because of calling two functions. Is there any other way to acieve this through a single call ?

Thanks,
Mahantesh


Hi,
I've never used ippiRotate_... for 90, 180, 270 degree rotations, instead I use a combination of mirror and/or transpose functions. I never had time to check if it was faster than ippiRotate but at least I'm sure to get an exact rotation (no rounding...).

For a 90 degree rotation :
ippiMirror_8u_C1R(pSrc, srcStep, pTempBuffer, srcStep, srcSize, ippAxsHorizontal);
ippiTranspose_8u_C1R(pTempBuffer, srcStep, pDst, dstStep, dstSize);
with dstSize.width = srcSize.height...

For a 270 degree rotation :
ippiTranspose_8u_C1R(pSrc, srcStep, pTempBuffer, dstStep, srcSize);
ippiMirror_8u_C1R(pTempBuffer, dstStep, pDst, dstStep, dstSize, ippAxsHorizontal);

For a 180 degree rotation :
ippiMirror_8u_C1R(pSrc, srcStep, pDst, dstStep, roiSize, ippAxsBoth);


Matthieu

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