HOG

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

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ID 790148

Date 3/22/2024

Version

Public

Visible to Intel only — GUID: GUID-685CE618-A63E-4026-B414-161F98D7B37A

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HOG

Computes the HOG descriptor.

Syntax

IppStatus ippiHOG_<mod>(const Ipp<srcDatatype>* pSrc, int srcStep, IppiSize roiSize, const IppiPoint* pLocation, int nLocations, Ipp32f* pDst, const IppiHOGSpec* pHOGSpec, IppiBorderType borderID, Ipp<srcDatatype> borderValue, Ipp8u* pBuffer);

Supported values for mod:

8u32f_C1R

16u32f_C1R

16s32f_C1R

32f_C1R

IppStatus ippiHOG_<mod>(const Ipp<srcDatatype>* pSrc, int srcStep, IppiSize roiSize, const IppiPoint* pLocation, int nLocations, Ipp32f* pDst, const IppiHOGSpec* pHOGCtx, IppiBorderType borderID, Ipp<srcDatatype> borderValue[3], Ipp8u* pBuffer);

Supported values for mod:

8u32f_C3R

16u32f_C3R

16s32f_C3R

32f_C3R

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 ROI.

srcStep

Distance, in bytes, between the starting points of consecutive lines in the source image.

roiSize

Size of the source image ROI, in pixels.

pLocation

Pointer to the array with detection window locations.

nLocations

Number of locations.

pDst

Pointer to the HOG descriptor.

pHOGCtx, pHOGSpec

Pointer to the HOG context/specification structure.

borderID

Type of border. Possible values are:

ippBorderConst	Values of all border pixels are set to a constant.
ippBorderRepl	Border is replicated from the edge pixels.
ippBorderInMem	Border is obtained from the source image pixels in memory.
ippBorderMirror	Border pixels are mirrored from the source image boundary pixels.

Mixed borders are also supported. They can be obtained by the bitwise operation OR between ippBorderRepl and ippBorderInMemTop, ippBorderInMemBottom, ippBorderInMemLeft, ippBorderInMemRight.

borderValue

Constant value to assign to pixels of the constant border. This parameter is applicable only to the ippBorderConst border type.

pBuffer

Pointer to the work buffer.

Description

This function computes the HOG descriptor over defined locations of the detection window. Flavors with the C1 suffix operate on one-channel (gray) images, and C3 flavors operate on color images.

Before using this function, compute the size of the context structure, work buffer, and descriptor using the HOGGetSize, HOGGetBufferSize, and HOGGetDescriptorSize functions, respectively. To initialize the HOG context structure, use the HOGInit function.

Return Values

ippStsNoErr	Indicates no error. Any other value indicates an error or a warning.
ippStsNullPtrErr	Indicates an error when one of the specified pointers is `NULL`.
ippStsContextmatchErr	Indicates an error when the context parameter does not match the operation.
ippStsStepErr	Indicates an error when srcStep is less than, or equal to zero.
ippStsNotEvenStepErr	Indicates an error when srcStep is not divisible by input data type size.
ippStsBorderErr	Indicates an error when borderID has an illegal value.
ippStsSizeErr	Indicates an error when roiSize is less than, or equal to zero.

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 computing HOG descriptor using Intel(R) Integrated Performance Primitives (Intel(R) IPP) functions:
//     ippiHOGGetSize
//     ippiHOGInit
//     ippiHOGGetBufferSize
//     ippiHOGGetDescriptorSize
//     ippiHOG_8u32f_C1R


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

#define WIND_WIDTH  64  /* detection window width  */
#define WIND_HEIGHT 128 /* detection window 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 */

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

static IppiHOGConfig config = { /* HOG configure structure */
    1,         /* Use OpenCV compatible output format */
    8,         /* Cell size (pixels) */
    16,        /* Block size (pixels) */
    8,         /* Block stride size (pixels) */
    9,         /* Number of bins (orientations) in the histogram */
    1.0f,       /* Sigma value (in the applied Gaussian) */
    0.2f,        /* Threshold value (applied for normalization) */
    {WIND_WIDTH, WIND_HEIGHT}, /* Size (width and height in pixels) of detection window */
};

int main(void)
{
    IppStatus status = ippStsNoErr;
    Ipp8u* pSrc = NULL;       /* Pointers to source/destination/feature images */
    int srcStep = 0;          /* Steps, in bytes, through the source/destination/feature images */
    IppiSize roiSize = { WIND_WIDTH, WIND_HEIGHT };    /* Size of source ROI in pixels */
    const Ipp8u borderValue = 0;
    IppiHOGSpec* pHOGctx = NULL;    /* Pointer to the HOG context  */
    int hogCtxSize = 0, hogBuffSize = 0, winBuffSize = 0; /* Sizes of buffers */
    Ipp8u* pBuffer = NULL;          /* Pointer to the work buffer */
    IppiPoint loc[] = { { 0, 0 }, { 2, 1 }, { 4, 2 }, { 6, 3 } }; /* Locations of detection window */
    int numLocs = sizeof(loc) / sizeof(IppiPoint);
    Ipp32f* pDescriptor = NULL; /* HOG descriptor */

    check_sts( status = ippiHOGGetSize(&config, &hogCtxSize) )  /* Get size of HOG context */

    pHOGctx = (IppiHOGSpec*)ippsMalloc_8u(hogCtxSize);
    check_sts( status = ippiHOGInit(&config, pHOGctx) ) /* Initialize HOG context */

    pSrc = ippiMalloc_8u_C1(roiSize.width, roiSize.height, &srcStep);

    /* Compute the temporary work buffer size */
    check_sts( status = ippiHOGGetBufferSize(pHOGctx, roiSize, &hogBuffSize) )

    pBuffer = ippsMalloc_8u(hogBuffSize);

    /* Compute size of HOG descriptor */
    check_sts( status = ippiHOGGetDescriptorSize(pHOGctx, &winBuffSize) )

    pDescriptor = (Ipp32f*)ippsMalloc_8u(numLocs*winBuffSize);

    check_sts( status = ippiHOG_8u32f_C1R(pSrc, srcStep, roiSize, /* Compute HOG descriptor */
        loc, numLocs, pDescriptor, pHOGctx, ippBorderConst, borderValue, pBuffer) )

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

Parent topic: Histogram of Oriented Gradients (HOG) Descriptor

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