Developer Reference

  • 2020
  • 10/21/2020
  • Public Content
Contents

LineSuppression

Implements the line suppression algorithm.

Syntax

IppStatus ippiLineSuppression_8u_C1R(const Ipp8u*
pSrc
, int
srcStep
, const Ipp8u*
pFeature
, int
featureStep
, Ipp8u*
pDst
, int
dstStep
, IppiSize
roiSize
, IppiDifferentialKernel
filterType
, IppiMaskSize
filterMask
, Ipp32u
avgWndSize
, float
threshold
, IppiBorderType
borderType
, Ipp8u
borderValue
, Ipp8u*
pBuffer
);
Include Files
ippcv.h
Domain Dependencies
Headers:
ippcore.h
,
ippvm.h
,
ipps.h
,
ippi.h
Libraries:
ippcore.lib
,
ippvm.lib
,
ipps.lib
,
ippi.lib
Parameters
pSrc
Pointer to the source image.
srcStep
Distance, in bytes, between the starting points of consecutive lines in the source image.
pFeature
Pointer to the feature points image.
featureStep
Distance, in bytes, between the starting points of consecutive lines in the feature points image.
pDst
Pointer to the destination image.
dstStep
Distance, in bytes, between the starting points of consecutive lines in the destination image.
roiSize
Size of the source and destination image ROI, in pixels.
filterType
Type of the derivative operator. Possible values are:
ippKernelSobel
Sobel filter
ippKernelScharr
Scharr filter
ippKernelCentralDiff
Central differences operator
filterMask
Size of the derivative filter aperture. The list of possible values depends on the
filterType
value:
Filter Type
Filter Mask
ippKernelSobel
ippMskSize3x3
,
ippMskSize5x5
ippKernelScharr
ippMskSize3x3
ippKernelCentralDiff
ippMskSize3x3
avgWndSize
Linear size of a neighborhood block for averaging.
threshold
Line suppression threshold.
borderType
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.
Mixed borders are also supported. They can be obtained by the bitwise operation OR between
ippBorderRepl
or
ippBorderConst
and the following flags:
  • ippBorderInMemTop
  • ippBorderInMemBottom
  • ippBorderInMemLeft
  • ippBorderInMemRight
Each of these flags means that for the corresponding border the outside pixels of the source image are in memory.
borderValue
Constant value(s) to assign to pixels of the constant border. This parameter is applicable only to the
ippBorderConst
border type.
pBuffer
Pointer to the work buffer. To calculate the size of the temporary buffer, use the LineSuppressionGetBufferSize function.
Description
The
ippiLineSuppression
function implements the line suppression algorithm. This function uses two input images: the original image and feature points image containing the lines (edges) and corners. This function performs the following steps:
  1. Computes
    I
    (
    x
    ,
    y
    )
    x
    and
    I
    (
    x
    ,
    y
    )
    y
    gradients for each (
    x
    ,
    y
    ) pixel of the image. The function computes gradients using the derivative operator specified by the
    filterType
    and
    filterMask
    parameters.
  2. Computes products of the gradients at each (
    x
    ,
    y
    ) pixel of the image:
  3. Performs averaging of the products of gradients over a rectangular neighborhood block at each pixel of the image. The block size is specified by the
    avgWndSize
    value.
  4. Defines 2x2 gradient covariance matrix
    H
    (
    x
    ,
    y
    )
    over a rectangular neighborhood block for each (
    x
    ,
    y
    ) pixel of the image.
  5. For each (
    x
    ,
    y
    ) pixel of the image checks the condition below. If the condition is true, the considered point is not a feature point.
    where
    • threshold
      is the line suppression threshold value passed to the function
    • λ
      1
      2
      are eigenvalues of the matrix
      H
      (
      x
      ,
      y
      )
      . If both eigenvalues have large positive values, the point belongs to a corner. If λ
      1
      is much bigger than λ
      2
      , the function clears out the candidate point.
The first and third stages of the function algorithm are filtering operations; they use border processing approach that is specified by the
borderType
parameter.
Before using this function, compute the size of the external work buffer using the LineSuppressionGetBufferSize function.
Return Values
ippStsNoErr
Indicates no error.
ippStsNullPtrErr
Indicates an error when
pSrc
,
pFeature
,
pDst
, or
pBufferSize
is
NULL
.
ippStsSizeErr
Indicates an error in the following cases:
  • when
    roiSize
    is less than, or equal to zero
  • when
    avgWndSize
    is equal to zero
ippStsNotEvenStepErr
Indicates an error when one of the step values is not divisible by 4 for floating point images.
ippStsFilterTypeErr
Indicates an error when
filterType
has an illegal value.
ippStsMaskSizeErr
Indicates an error when
filterMask
has an illegal value.
ippStsBorderErr
Indicates an error when
borderType
has an illegal value.
ippStsStepErr
Indicates an error when
srcStep
or
dstStep
has a negative value.
ippStsInplaceModeNotSupportedErr
Indicates an error when
pFeature
and
pDst
point to the same image.

Example



    
/******************************************************************************* * Copyright 2015-2020 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 Line Suppression // using Intel(R) Integrated Primitives (Intel(R) IPP) functions: // ippiLineSuppressionGetBufferSize // ippiLineSuppression_8u_C1R #include <stdio.h> #include "ipp.h" #define WIDTH 128 /* image width */ #define HEIGHT 64 /* 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 */ int main(void) { IppStatus status = ippStsNoErr; Ipp8u* pSrc = NULL, *pDst = NULL, *pFeature = NULL; /* Pointers to source/destination/feature images */ int srcStep = 0, dstStep = 0, featureStep = 0; /* Steps, in bytes, through the source/destination/feature images */ IppiSize roiSize = { WIDTH, HEIGHT }; /* Size of source/destination ROI in pixels */ IppiMaskSize filterMask = ippMskSize3x3; /* Linear size of derivative filter aperture */ Ipp32u avgWndSize = 1; /* Neighbourhood block size for smoothing */ Ipp32u numChannels = 1; Ipp32f threshold = 5.0f; const Ipp8u borderValue = 0; Ipp8u* pBuffer = NULL; /* Pointer to the work buffer */ int bufSize = 0; IppiDifferentialKernel filterType = ippFilterSobel; /* Type of derivative operator */ pSrc = ippiMalloc_8u_C1(roiSize.width, roiSize.height, &srcStep); pDst = ippiMalloc_8u_C1(roiSize.width, roiSize.height, &dstStep); pFeature = ippiMalloc_8u_C1(roiSize.width, roiSize.height, &featureStep); /* Computes the temporary work buffer size */ check_sts( status = ippiLineSuppressionGetBufferSize(roiSize, filterMask, avgWndSize, ipp8u, numChannels, &bufSize) ) pBuffer = ippsMalloc_8u(bufSize); /* Line Suppression processing */ check_sts( status = ippiLineSuppression_8u_C1R(pSrc, srcStep, pFeature, featureStep, pDst, dstStep, roiSize, filterType, filterMask, avgWndSize, threshold, ippBorderRepl, borderValue, pBuffer) ) EXIT_MAIN ippiFree(pSrc); ippiFree(pDst); ippiFree(pFeature); printf("Exit status %d (%s)\n", (int)status, ippGetStatusString(status)); return (int)status; }

Product and Performance Information

1

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Notice revision #20110804