Need help on Image rotation.
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
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Re: Need help on Image rotation.
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
| |
Re: Need help on Image rotation.
Hi Matthieu,
Thank you for your suggestion. Yes, we recomment to use ippiMirror to do special rotation
like 90,180,270.
To mahantesh,
if use ippiRotate, the no-intergate interpolation, round issue
are unavaidable. ippiRotate provide one parameter IPPI_SMOOTH_EDGE to make edge look better. But the
black strips may still visiable. how width of the strips in your test? does it affect your result?
Here
is small piece of code for your reference.
IppiSize srcTempSize = {w, h};
IppiSize dstTempSize = {h, w};
IppiRect srcTempRect = { 0, 0,w, h
};
IppiRect dstTempRect = { 0, 0,h, w };
double xTempShift = 0.0;
double yTempShift = 1.0*w; //
conterwise rotate 90 degree, origin (0, 0) will be (0, w) after rotation, so the y shift is w
/* Use this function if you need to rotate an image about an arbitrary center (xCenter, yCenter) rather than the
origin (0,0), we will rotate the image by 0, 0 first, so it is not necessary to call it here
/*
//ippiGetRotateShift(0.0, 0.0, 90.0, &xTempShift, &yTempShift);
ippiSet_8u_C4R ( 0, (Ipp8u*) dstTemp->imageData, dstTemp->widthStep, dstTempSize );
status=ippiRotate_8u_C4R ( (Ipp8u*) srcTemp->imageData, srcTempSize, srcTemp->widthStep, srcTempRect,
(Ipp8u*) dstTemp->imageData, dstTemp->widthStep, dstTempRect, 90.0,
xTempShift,
yTempShift, IPPI_INTER_LINEAR|IPPI_SMOOTH_EDGE);
//my test: the rotate operation will show 1 pixel width black
line on upper of the rotated image)
Best Regards,
Ying
| |
Re: Need help on Image rotation.
Hi Matthieu,
Thank you for your suggestion. Yes, we
recomment to use ippiMirror to do special rotation like 90,180,270.
To mahantesh,
if use
ippiRotate, the no-intergate interpolation, round issue are unavaidable. ippiRotate provide one parameter
IPPI_SMOOTH_EDGE to make edge look better. But the black strips may still visiable. how width of the strips in
your test? does it affect your result?
Here is small piece of code for your reference.
IppiSize srcTempSize = {w, h};
IppiSize dstTempSize = {h, w};
IppiRect srcTempRect = { 0, 0,w, h
};
IppiRect dstTempRect = { 0, 0,h, w };
double xTempShift = 0.0;
double yTempShift = 1.0*w; //
conterwise rotate 90 degree, origin (0, 0) will be (0, w) after rotation, so the y shift is w
/* Use this function if you need to rotate an image about an arbitrary center (xCenter, yCenter) rather than the
origin (0,0), we will rotate the image by 0, 0 first, so it is not necessary to call it here
/*
//ippiGetRotateShift(0.0, 0.0, 90.0, &xTempShift, &yTempShift);
ippiSet_8u_C4R ( 0, (Ipp8u*) dstTemp->imageData, dstTemp->widthStep, dstTempSize );
status=ippiRotate_8u_C4R ( (Ipp8u*) srcTemp->imageData, srcTempSize, srcTemp->widthStep, srcTempRect,
(Ipp8u*) dstTemp->imageData, dstTemp->widthStep, dstTempRect, 90.0,
xTempShift, yTempShift,
IPPI_INTER_LINEAR|IPPI_SMOOTH_EDGE);
//my test: the rotate operation will show 1 pixel width black line on upper
of the rotated image)
Best Regards,
Ying
Hi Ying,
Thanks for the pointers to rotate the image. The rotation is working good for all the
resolutions except for 160 x 120. Is there anything we need to take care for lower resolutions?
Thanks,
Mahantesh
| |
Re: Need help on Image rotation.
Hi Ying,
I am using IPP 6.1.1.035. For rotation i am using ippiRotate followed by ippiMirror functions to remove the
mirroring effect. The image looks like folded lines for the resoltion 160 x 120.
Thanks,
Mahantesh
| |
Re: Need help on Image rotation.
Hi Mahantesh,
Thank you for your reply. I don't rememeber there is known issue for rotating 160x120
specially.
could you send me a example?
Best Regards,
Ying
| |
Re: Need help on Image rotation.
Hi Mahantesh,
Thank you for your reply. I don't rememeber
there is known issue for rotating 160x120 specially.
could you send me a example?
Best Regards,
Ying
Hi Ying,
I tested this behavior on different systems. On some systems it works good but on some other systems it is like
images is turned in to roles. I tried to take print screen but it is coming blank. We are actually rotating video with
the help of roation functions.
One more problem i am facing is, on some systems the rotation along with mirroring function works fine but on some
systmes we are getting mirror effect. Not able to judge when to apply mirroring functions and when not to apply. Please
let me know when to use mirroring functions and when not to use.
Thanks,
Mahantesh
| |
Re: Need help on Image rotation.
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
We have found that Transpose is faster than Rotate at the 90-degree rotations, and yes, also avoid any potential
rounding artefacts. I presume most would want 90-degree rotations to be exact. You can actually improve slightly on the
speed by avoiding the Mirroring-calls. This can be done by effectively flipping either the source or the destination
image "during" the transposing. This can be done by setting a negative stride and also adjust the associated pointer to
point at the start of the last row/line of the image.
Otherwise, you may consider cutting down on memory use by
skipping the temporary buffer and do the mirroring in-place in the 'dst' buffer.
Regards,
- Jay
| |
Re: Need help on Image rotation.
Hi Matthieu,
Thank you for your suggestion. Yes, we
recomment to use ippiMirror to do special rotation like 90,180,270.
To mahantesh,
if use
ippiRotate, the no-intergate interpolation, round issue are unavaidable. ippiRotate provide one parameter
IPPI_SMOOTH_EDGE to make edge look better. But the black strips may still visiable. how width of the strips in
your test? does it affect your result?
Here is small piece of code for your reference.
IppiSize srcTempSize = {w, h};
IppiSize dstTempSize = {h, w};
IppiRect srcTempRect = { 0, 0,w, h
};
IppiRect dstTempRect = { 0, 0,h, w };
double xTempShift = 0.0;
double yTempShift = 1.0*w; //
conterwise rotate 90 degree, origin (0, 0) will be (0, w) after rotation, so the y shift is w
/* Use this function if you need to rotate an image about an arbitrary center (xCenter, yCenter) rather than the
origin (0,0), we will rotate the image by 0, 0 first, so it is not necessary to call it here
/*
//ippiGetRotateShift(0.0, 0.0, 90.0, &xTempShift, &yTempShift);
ippiSet_8u_C4R ( 0, (Ipp8u*) dstTemp->imageData, dstTemp->widthStep, dstTempSize );
status=ippiRotate_8u_C4R ( (Ipp8u*) srcTemp->imageData, srcTempSize, srcTemp->widthStep, srcTempRect,
(Ipp8u*) dstTemp->imageData, dstTemp->widthStep, dstTempRect, 90.0,
xTempShift, yTempShift,
IPPI_INTER_LINEAR|IPPI_SMOOTH_EDGE);
//my test: the rotate operation will show 1 pixel width black line on upper
of the rotated image)
Best Regards,
Ying
Hi Ying,
For the rotate operation using ippiRotate_8u_C3R(), we are getting black line on the rotated image. For resolutions
160x120,176x144,320x240,352x288 the line is thicker and can be easily identified. For 640x480 and higher resolutions its
very thin. Is there any way to completely remove these lines? can this be fixed from IPP library? If yes then when this
will be available? or any fix can be given from the application using IPP library?
Thanks,
Mahantesh
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