WarpPerspective

Syntax

Parameters

pSrc	Pointer to the source image origin.An array of separate pointers to each plane in case of data in planar format.
srcSize	Size in pixels of the source image.
srcStep	Distance in bytes between starts of consecutive lines in the source image buffer.
srcRoi	Region of interest in the source image (of the IppiRect type).
pDst	Pointer to the destination image origin. An array of separate pointers to each plane in case of data in planar format.
dstStep	Distance in bytes between starts of consecutive lines in the destination image buffer.
dstRoi	Region of interest in the destination image (of the IppiRect type).
coeffs	The perspective transform coefficients.
interpolation	Specifies the interpolation mode. Use one of the following values: IPPI_INTER_NN nearest neighbor interpolation IPPI_INTER_LINEAR linear interpolation IPPI_INTER_CUBIC cubic interpolation IPPI_SMOOTH_EDGE use edge smoothing in addition to one of the above modes.

Description

The function ippiWarpPerspective is declared in the ippi.h file. It operates with ROI (see ROI Processing in Geometric Transforms).

This perspective warp function transforms the source image pixel coordinates (x,y) according to the following formulas:

x' = (c₀₀* x + c₀₁* y + c₀₂)/ (c₂₀* x + c₂₁* y + c₂₂)

y' = (c₁₀* x + c₁₁* y + c₁₂)/ (c₂₀* x + c₂₁* y + c₂₂)

where x' and y' denote the pixel coordinates in the transformed image, and c_ij are the perspective transform coefficients passed in the array coeffs.

The transformed part of the image is resampled using the interpolation mode specified by the interpolation parameter, and written to the destination image ROI.

Note

IPPI_SMOOTH_EDGE is the artificial method. It is not universal: in some cases it can improve the image, but in some other cases it is not effective. For example, the smoothing does not improve the images with the high contrast borders. In such cases don't use edge smoothing.

Figure “Perspective Transform of an Image” gives an example of applying the perspective transform function ippiWarpPerspective to a sample image.

To estimate how the source image ROI will be transformed by the ippiWarpPerspective function, use functions ippiWarpPerspectiveQuad and ippiGetPerspectiveBound. To calculate coefficients of the perspective transform that maps source ROI to a given quadrangle, use ippiGetPerspectiveTransform function.

Example “Using Intel IPP Functions for Perspective Warping” shows how to use the function ippiWarpPerspective_32f_C1R.

Return Values

ippStsNoErr	Indicates no error. Any other value indicates an error or a warning.
ippStsNullPtrErr	Indicates an error condition if one of the specified pointer is NULL.
ippStsSizeErr	Indicates an error condition if any image dimension has zero or negative value.
ippStsStepErr	Indicates an error condition if srcStep or dstStep has a zero or negative value.
ippStsRectErr	Indicates an error condition if width or height of the intersection of the srcRoi and source image is less than or equal to 1.
ippStsInterpolationErr	Indicates an error condition if interpolation has an illegal value.
ippStsCoeffErr	Indicates an error condition if coefficient values are invalid.
ippStsWrongIntersectROIErr	Indicates an error condition if srcRoi has no intersection with the source image.
ippStsWrongIntersectQuad	Indicates a warning that no operation is performed if the transformed source ROI has no intersection with the destination ROI.