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 thefilterTypevalue:Filter TypeFilter MaskippKernelSobelippMskSize3x3,ippMskSize5x5ippKernelScharrippMskSize3x3ippKernelCentralDiffippMskSize3x3
- 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 betweenippBorderReplorippBorderConstand the following flags:- ippBorderInMemTop
- ippBorderInMemBottom
- ippBorderInMemLeft
- ippBorderInMemRight
- borderValue
- Constant value(s) to assign to pixels of the constant border. This parameter is applicable only to theippBorderConstborder 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:- ComputesI(x,y)andxI(x,y)gradients for each (yx,y) pixel of the image. The function computes gradients using the derivative operator specified by thefilterTypeandfilterMaskparameters.
- Computes products of the gradients at each (x,y) pixel of the image:
- Performs averaging of the products of gradients over a rectangular neighborhood block at each pixel of the image. The block size is specified by theavgWndSizevalue.
- Defines 2x2 gradient covariance matrixH(over a rectangular neighborhood block for each (x,y)x,y) pixel of the image.
- 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
- thresholdis the line suppression threshold value passed to the function
- λ1*λ2are eigenvalues of the matrixH(. If both eigenvalues have large positive values, the point belongs to a corner. If λx,y)1is much bigger than λ2, 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 whenpSrc,pFeature,pDst, orpBufferSizeisNULL.
- ippStsSizeErr
- Indicates an error in the following cases:
- whenroiSizeis less than, or equal to zero
- whenavgWndSizeis 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 whenfilterTypehas an illegal value.
- ippStsMaskSizeErr
- Indicates an error whenfilterMaskhas an illegal value.
- ippStsBorderErr
- Indicates an error whenborderTypehas an illegal value.
- ippStsStepErr
- Indicates an error whensrcStepordstStephas a negative value.
- ippStsInplaceModeNotSupportedErr
- Indicates an error whenpFeatureandpDstpoint to the same image.
Example
/*******************************************************************************
* Copyright 2015-2021 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;
}