Rotating an Image Using Intel IPP Warp
Functions
Starting with the 9.0 version, Intel IPP enables you
to use the
ippiWarpAffine<Interpolation>
functions to implement
rotation of an image using pre-calculated affine coefficients based on rotation
parameters (angle,
x
-,
y
-shifts ). To obtain affine coefficients for the
specified rotation parameters, you can apply the
ippiGetRotateTransform
function. This function computes the
affine coefficients for the transform that rotates an image by the specified
angle around (0, 0) and shifts the image by the specified
x-
and
y-
shift values.
You can apply the computed bounding box to change the
x
-,
y
-shifts of the rotated image to fit the transformed
image to the destination ROI. To compute the bounding box for the affine
transform, use the
ippiGetAffineBound
function.
Before calling the warp affine processing function, you need to:
- Compute the size of the specification structure for affine warping with the specified interpolation method using theippiWarpAffineGetSizefunction
- Initialize the specification structure using theippiWarpAffine<Interpolation>Initfunction
- Compute the size of the temporary work buffer required for warping usingippiWarpAffineGetSizeand pass pointer to the buffer to the processing function
The code example below demonstrates how to perform image rotation using
the Intel IPP affine warping functions:
IppStatus warpAffine(Ipp8u* pSrc, IppiSize srcSize, int srcStep, Ipp8u* pDst, IppiSize dstSize, int dstStep, const double coeffs[2][3])
{
int specSize = 0, initSize = 0, bufSize = 0;
Ipp8u* pBuffer = NULL;
const Ipp32u numChannels = 3;
IppiPoint dstOffset = {0, 0};
IppiBorderType borderType = ippBorderConst;
IppiWarpDirection direction = ippWarpForward;
Ipp64f pBorderValue[numChannels];
IppiWarpSpec* pSpec = NULL;
IppStatus status = ippStsNoErr;
for (int i = 0; i < numChannels; ++i) pBorderValue[i] = 255.0;
/* Spec and init buffer sizes */
status = ippiWarpAffineGetSize(srcSize, dstSize, ipp8u, coeffs, ippLinear, direction, borderType,
&specSize, &initSize);
/* Allocate memory */
pSpec = (IppiWarpSpec*)ippsMalloc_8u(specSize);
/* Affine transform data initialization */
if (status >= ippStsNoErr) status = ippiWarpAffineLinearInit(srcSize, dstSize, ipp8u, coeffs, direction, numChannels, borderType, pBorderValue, 0, pSpec);
/* Get work buffer size */
if (status >= ippStsNoErr) status = ippiWarpGetBufferSize(pSpec, dstSize, &bufSize);
pBuffer = ippsMalloc_8u(bufSize);
/* Affine transform processing */
if (status >= ippStsNoErr) status = ippiWarpAffineLinear_8u_C3R(pSrc, srcStep, pDst, dstStep, dstOffset, dstSize, pSpec, pBuffer);
/* Free memory */
ippsFree(pSpec);
ippsFree(pBuffer);
return status;
}
For more information about the Intel IPP Warp functions, refer to the
Intel IPP Developer Reference
.