July 2, 2009 1:41 PM PDT
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 ?
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);
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?
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)
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?
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?
Maybe same. What is symptom when resize the 160x120?
Best Regards, Ying
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.
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.
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.
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?
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?
we are facing one problem while rotating image data for 90 degree rotation, please find the code snippet below. Some problem with dstSize in ippiTranspose_8u_C3R() function, this function is crashing. If instead of dstSize, if we pass srcSize, it is working fine.
Please let us know if you have faced similar problem or is it the expected behavior that we should pass srcSize where actually we have to pass dstSize or if any resolution for the crash.
I'm looking into the ippiRotate issue and get back to you if any findings.
About the ippiTranspose function, right, you should use the size same as the source input, see the description of the function' parameter in ippiman.pdf, roiSize - Size of the source ROI in pixels.
So for 90 degeree rotation, the pTempBuffer is a source with (srcSize.width, srcSize.heigh), so you will enter srcSize there.
for 270 degree rotation, you call ippiTranspose first, the pSrc is the input source of the function, so it also needs srcSize.
We rotate a 227x149 image to 149x227 image. I add black edge to dst image, so you can see there is the white line on the upper of image clearly. It is the line I mentioned last time. It is common rounding artefacts because pixel in IPP affine transforms (include rotate operations) is not square but is a point.
For workaround you can just simple to remove it by subtract 1 from yshift or xShift. for example,
The line is gone. (It is just sample, for who is using ippiRotate and has same problem, please consider such kind of modification based on your input image.)
