Remap

Intel® Integrated Performance Primitives Developer Guide and Reference

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ID 790148

Date 11/07/2023

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Remap

Performs the look-up coordinate mapping of pixels of the source image.

Syntax

Case 1: Operation on pixel-order data

IppStatus ippiRemap_<mod>(const Ipp<datatype>* pSrc, IppiSize srcSize, int srcStep, IppiRect srcRoi, const Ipp32f* pxMap, int xMapStep, const Ipp32f* pyMap, int yMapStep, Ipp<datatype>* pDst, int dstStep, IppiSize dstRoiSize, int interpolation);

Supported values for mod:

8u_C1R	16u_C1R	16s_C1R	32f_C1R
8u_C3R	16u_C3R	16s_C3R	32f_C3R
8u_C4R	16u_C4R	16s_C4R	32f_C4R
	16u_AC4R	16s_AC4R	32f_AC4R

IppStatus ippiRemap_<mod>(const Ipp<datatype>* pSrc, IppiSize srcSize, int srcStep, IppiRect srcRoi, const Ipp64f* pxMap, int xMapStep, const Ipp64f* pyMap, int yMapStep, Ipp<datatype>* pDst, int dstStep, IppiSize dstRoiSize, int interpolation);

Supported values for mod:

64f_C1R

64f_C3R

64f_C4R

64f_AC4R

IppStatus ippiRemap_8u_AC4R(const Ipp<datatype>* pSrc, IppiSize srcSize, int srcStep, IppiRect srcRoi, const Ipp32f* pxMap, int xMapStep, const Ipp32f* pyMap, int yMapStep, Ipp<datatype>* pDst, int dstStep, IppiSize dstRoiSize, int interpolation);

Include Files

ippi.h

Domain Dependencies

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

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

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 the starting points of consecutive lines in the source image buffer.
srcRoi	Region of interest in the source image (of the IppiRect type).
pxMap, pyMap	Pointers to the starts of 2D buffers, containing tables of the x- and y-coordinates.
xMapStep, yMapStep	Steps, in bytes, through the buffers containing tables of the x- and y-coordinates.
pDst	Pointer to the destination image ROI. An array of separate pointers to ROI in each plane for planar image.
dstStep	Distance, in bytes, between the starting points of consecutive lines in the destination image buffer.
dstRoiSize	Size of the destination ROI in pixels.
interpolation	Specifies the interpolation mode. Possible values are:
	IPPI_INTER_NN - nearest neighbor interpolation
	IPPI_INTER_LINEAR - linear interpolation
	IPPI_INTER_CUBIC - cubic interpolation
	IPPI_INTER_LANCZOS - interpolation with Lanczos window
	IPPI_INTER_CUBIC2P_CATMULLROM - Catmull-Rom spline
	the following flag is used additionally to the above modes:
	IPPI_SMOOTH_EDGE - edge smoothing

Description

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

This function transforms the source image by remapping its pixels. Pixel remapping is performed using pxMap and pyMap buffers to look-up the coordinates of the source image pixel that is written to the target destination image pixel. The application has to supply these look-up tables. The remapping of the source pixels to the destination pixels is made according to the following formula:

dst_pixel[i, j]=src_pixel[pxMap[i, j], pyMap[i, j]]

where i,j are the x- and y-coordinates of the target destination image pixel dst_pixel;

pxMap[i, j] contains the x- coordinates of the source image pixels src_pixel that are written to dst_pixel;

pyMap[i, j] contains the y- coordinates of the source image pixels src_pixel that are written to dst_pixel.

If the referenced coordinates correspond to a pixel outside of the source ROI, and the flag IPPI_SMOOTH_EDGE is not set, then no mapping of the source pixel is performed.

Figure “Remapping the Sample Image” gives an example of applying the function ippiRemap to a sample image that is a square grid of alternating blue, red, and green lines.

Remapping the Sample Image

The transformed part of the image is resampled using the interpolation method specified by the interpolation parameter, and is written to the destination image ROI. The function can be used with or without edge smoothing. The pseudo code below shows how it works.

The function works without edge smoothing - the flag IPPI_SMOOTH_EDGE is not set:

if ( xMap < srcRoi . x || xMap > srcRoi . x + srcRoi . width -1 || yMap < srcRoi . y || yMap > srcRoi . y + srcRoi . height -1)

not fill dst /* do not remap */

else

fill dst with Interpolate(Src, xMap, yMap) /* remap */

The function works with edge smoothing - the flag IPPI_SMOOTH_EDGE is set:

if (xMap < srcRoi.x - 1 || xMap > srcRoi.x+srcRoi.width || yMap < srcRoi.y - 1 || yMap > srcRoi.y+srcRoi.height)

not fill dst /* do not remap */

else if (xMap < srcRoi.x || xMap > srcRoi.x+srcRoi.width-1 || yMap < srcRoi.y || yMap > srcRoi.y+srcRoi.height-1)

fill dst with Interpolate(Src, fillvalue, xMap, yMap) /* smoothing */

else

fill dst with Interpolate(Src, xMap, yMap) /* remap */

If the width or height of the input image pSrc is insufficient for the interpolation method specified by the parameter interpolation, the function uses interpolation with a smaller number of pixels for both width and height dimensions. See the following pseudocode:

if (width < 6 || height < 6) {
    inter== lanczos ? inter = cubic;
    if ( (width < 4 || height < 4) && ( inter == cubic || inter == catmullrom) )
          inter = linear;
    if (width == 1 || height == 1)
          inter = nearest;
}

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 pointers is NULL.
ippStsSizeErr	Indicates an error condition if srcSize or dstRoiSize has a field with zero or negative value.
ippStsStepErr	Indicates an error condition if one of the srcStep, dstStep, xMapStep, or yMapStep has a zero or negative value.
ippStsInterpolationErr	Indicates an error condition if interpolation has an illegal value.
ippStsWrongIntersectROIErr	Indicates an error condition if srcRoi has no intersection with the source image.

Example

/*******************************************************************************
* Copyright 2015 Intel Corporation.
*
*
* This software and the related documents are Intel copyrighted materials, and your use of them is governed by
* the express license under which they were provided to you ('License'). Unless the License provides otherwise,
* you may not use, modify, copy, publish, distribute, disclose or transmit this software or the related
* documents without Intel's prior written permission.
* This software and the related documents are provided as is, with no express or implied warranties, other than
* those that are expressly stated in the License.
*******************************************************************************/

// A simple example of the source image transformation by remapping
// of its pixels using Intel(R) Integrated Primitives (Intel(R) IPP) function:
//     ippiRemap_8u_C1R


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

/* 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 */

int main(void)
{
    IppStatus status = ippStsNoErr;
    Ipp8u pSrc[4 * 4] =/* Pointers to source images */
    {   0, 1, 2, 3,
        4, 5, 6, 7,
        8, 9, 0, 1,
        2, 3, 4, 5 };
    Ipp8u pDst[4*4];              /* Pointers to destination images */
    int srcStep = 4, dstStep = 4; /* Steps, in bytes, through the source/destination images */
    IppiSize roiSize = { 4, 4 };  /* Size of source/destination ROI in pixels */
    Ipp32f pxMap[4 * 4] = {/* Pointer to x map */
        0, 1, 2, 3,
        0, 1, 2, 0,
        0, 1, 0, 0,
        0, 1, 2, 3 };
    Ipp32f pyMap[4 * 4] = {/* Pointer to y map */
        0, 0, 0, 0,
        1, 1, 1, 0,
        2, 2, 0, 0,
        3, 3, 3, 3 };
    int xStep = 16, yStep = 16;     /* Steps, in bytes, through the x and y maps */
    IppiRect rect = { 0, 0, 4, 4 }; /* Region of interest in the source image */

    check_sts( status = ippiRemap_8u_C1R(pSrc, roiSize, srcStep, rect, pxMap, xStep, pyMap, yStep,
        pDst, dstStep, roiSize, IPPI_INTER_LINEAR) )

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

Parent topic: Geometric Transform Functions

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Intel® Integrated Performance Primitives Developer Guide and Reference

Remap

Syntax

Include Files

Domain Dependencies

Parameters

Description

Return Values

Example