Intel® Integrated Performance Primitives (Intel® IPP) Developer Guide and Reference

ID 790148
Date 3/22/2024
Public

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Document Table of Contents

GetBilinearTransform

Computes bilinear transform coefficients to map the source ROI to the quadrangle with the specified vertex coordinates.

Syntax

IppStatus ippiGetBilinearTransform(IppiRect srcRoi, const double quad[4][2], double coeffs[2][4]);

Include Files

ippi.h

Domain Dependencies

Headers: ippcore.h, ippvm.h, ipps.h

Libraries: ippcore.lib, ippvm.lib, ipps.lib

Parameters

srcRoi

Region of interest in the source image (of the IppiRect type).

quad

Vertex coordinates of the quadrangle, to which the source ROI is mapped by the bilinear transform function.

coeffs

Output array. Contains the target bilinear transform coefficients.

Description

This function operates with ROI (see ROI Processing in Geometric Transforms).

This function is used as a support function for ippiWarpBilinear. It computes the coefficientscoeffs of thebilinear transform that maps the source rectangular ROI to the quadrangle with the specified vertex coordinates quad.

The first dimension [4] of the array quad[4][2] is equal to the number of vertices, and the second dimension [2] means x and y coordinates of the vertex. Quadrangle vertices have the following meaning:

quad[0] corresponds to the transformed top-left corner of the source ROI,

quad[1] corresponds to the transformed top-right corner of the source ROI,

quad[2] corresponds to the transformed bottom-right corner of the source ROI,

quad[3] corresponds to the transformed bottom-left corner of the source ROI.

Return Values

ippStsNoErr

Indicates no error. Any other value indicates an error.

ippStsSizeErr

Indicates an error condition if srcRoi has a size field with zero or negative value.

ippStsCoeffErr

Indicates an error condition if coefficient values are invalid.

ippStsRectErr

Indicates an error condition if width or height of the srcRoi is less than or equal to 1.

Example

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// A simple example of performing bilinear warping of an image
// using Intel(R) Integrated Performance Primitives (Intel(R) IPP) functions:
//     ippiWarpBilinearGetBufferSize
//     ippiGetBilinearTransform
//     ippiWarpBilinear_32f_C1R
//     ippiWarpBilinearBack_32f_C1R


#include <stdio.h>
#include "ipp.h"

#define WIDTH   8  /* source image width */
#define HEIGHT  8  /* source image height */

/* Next two defines are created to simplify code reading and understanding */
#define EXIT_MAIN exitLine:                                  /* Label for Exit */
#define check_sts(st) if((st) != ippStsNoErr) goto exitLine; /* Go to Exit if Intel(R) IPP function returned status different from ippStsNoErr */

static Ipp32f pSrc[WIDTH*HEIGHT] =/* Pointers to source images */
{
    1.f, 1.f, 1.f, 1.f, 1.f, 1.f, 1.f, 1.f,
    1.f, 1.f, 1.f, 5.f, 5.f, 1.f, 1.f, 1.f,
    1.f, 1.f, 5.f, 5.f, 5.f, 5.f, 1.f, 1.f,
    1.f, 5.f, 5.f, 5.f, 5.f, 5.f, 5.f, 1.f,
    1.f, 5.f, 5.f, 5.f, 5.f, 5.f, 5.f, 1.f,
    1.f, 1.f, 5.f, 5.f, 5.f, 5.f, 1.f, 1.f,
    1.f, 1.f, 1.f, 5.f, 5.f, 1.f, 1.f, 1.f,
    1.f, 1.f, 1.f, 1.f, 1.f, 1.f, 1.f, 1.f };
static const double quad[4][2] = /* Vertex coordinates of the quadrangle */
{
    { 1.0, 1.0 },
    { 8.0, 0.0 },
    { 6.0, 8.0 },
    { 2.0, 6.0 } };

/* Results of ippMalloc() are not validated because Intel(R) IPP functions perform bad arguments check and will return an appropriate status  */

int main(void)
{
    IppStatus status = ippStsNoErr;
    IppiSize srcSize = { WIDTH, HEIGHT }; /* Size of source ROI in pixels */
    IppiRect srcRoi = { 0, 0, WIDTH, HEIGHT };/* Region of interest in the source image */
    int srcStep = WIDTH * sizeof(Ipp32f), dstStep = srcStep, dstbStep = srcStep; /* Steps, in bytes, through the source/destination/back destination images */
    Ipp32f pDst[WIDTH*HEIGHT], pDstB[WIDTH*HEIGHT];/* Pointers to destination/back destination images */
    IppiSize dstSize = { WIDTH, HEIGHT };
    IppiRect dstbRoi = { 0, 0, WIDTH, HEIGHT }; /* Region of interest in the back destination image */
    IppiRect dstRoi  = { 0, 0, WIDTH, HEIGHT }; /* Region of interest in the destination image */
    double coeffs[2][4] = {0};
    int bufSize = 0, bufSizeB = 0; /* Work buffers size */
    Ipp8u* pBuffer = NULL,*pBufferB = NULL;

    check_sts( status = ippiSet_32f_C1R(2, pDst, srcStep, srcSize) )

    check_sts( status = ippiSet_32f_C1R(3, pDstB, srcStep, srcSize) )

    /* Computes bilinear transform matrix */
    check_sts( status = ippiGetBilinearTransform(srcRoi, quad, (double(*)[4])coeffs) )

    /* Computes the size of external buffer for bilinear transform */
    check_sts( status = ippiWarpBilinearGetBufferSize(srcSize, srcRoi, dstRoi, ippWarpForward, coeffs, IPPI_INTER_NN, &bufSize) )

    /* Computes the size of external buffer for Back bilinear transform */
    check_sts( status = ippiWarpBilinearGetBufferSize(dstSize, dstRoi, dstbRoi, ippWarpBackward, coeffs, IPPI_INTER_NN, &bufSizeB) )

    pBuffer  = ippsMalloc_8u(bufSize);
    pBufferB = ippsMalloc_8u(bufSizeB);

    /* Performs bilinear warping of an image */
    check_sts( status = ippiWarpBilinear_32f_C1R(pSrc, srcSize, srcStep, srcRoi, pDst, dstStep, dstRoi, coeffs, IPPI_INTER_NN, pBuffer) )

    /* Performs an inverse bilinear warping of an image */
    check_sts( status = ippiWarpBilinearBack_32f_C1R(pDst, dstSize, dstStep, dstRoi, pDstB, dstbStep, dstbRoi, coeffs, IPPI_INTER_NN, pBuffer) )

EXIT_MAIN
    ippsFree(pBuffer);
    ippsFree(pBufferB);
    printf("Exit status %d (%s)\n", (int)status, ippGetStatusString(status));
    return (int)status;
}