Computation of accumulator matrix for extension of Hough lines detection

computes the accumulator matrix used by the Hough lines detector from gradient images More...

IPSDKIPLFEATUREDETECTION_API image::ImagePtr	ipsdk::imaproc::fd::houghLinesGradient2dImg (const image::ImageConstPtr &pInGxGreyImg2d, const image::ImageConstPtr &pInGyGreyImg2d)
	wrapper function for computation of accumulator matrix of extended Hough lines detector detector, from 2 images of gradient (one along x-axis, the other along y) More...
IPSDKIPLFEATUREDETECTION_API image::ImagePtr	ipsdk::imaproc::fd::houghLinesGradient2dImg (const image::ImageConstPtr &pInGxGreyImg2d, const image::ImageConstPtr &pInGyGreyImg2d, const ipsdk::imaproc::attr::HoughLinesGradientImgParamsConstPtr &pHoughLinesImgParams, const ipsdk::ipReal32 orientationTolerance)
	wrapper function for computation of accumulator matrix of extended Hough lines detector detector, from 2 images of gradient (one along x-axis, the other along y) More...

Detailed Description

computes the accumulator matrix used by the Hough lines detector from gradient images

detection from gradient images

This algorithm computes, from a grey level 2d image, the accumulation matrix used to detect straight lines in the input image, using the implemented extension of Hough transform based on gradient orientation.

See HoughLinesGradient2d for more information

Attributes description

Attribute description for algorithm :

Name	ToolTip	Default Initializer
ipsdk::imaproc::attr::InGxGreyImg2d	[Input] 2d grey levels image of gradient computed along x-axis	X
ipsdk::imaproc::attr::InGyGreyImg2d	[Input] 2d grey levels image of gradient computed along y-axis	X
ipsdk::imaproc::attr::InOptHoughLinesGradientImgParams	[Input Optional] Parameters for Hough lines detection algorithm using 2 input gradient images	X
ipsdk::imaproc::attr::InOptHoughLinesOrientationTolerance	[Input Optional] Tolerance for orientation around estimated gradient direction	X
ipsdk::imaproc::attr::OutRealImg	[Output] image for processing operation (data contained in image buffer are reals)	customOutput (_pOutRealImg, outputHoughLinesGradient2dImg(_pInGxGreyImg2d,_pInOptHoughLinesGradientImgParams))

Global Rule description

Global rule description for algorithm :
ipsdk::imaproc::matchSizeAndType (_pInGxGreyImg2d,_pInGyGreyImg2d) && 
ipsdk::imaproc::customImageProperty (_pOutRealImg,
 ipsdk::imaproc::fd::houghLines2dCheckOutImgSzXEquals (_pInGxGreyImg2d,_pInOptHoughLinesGradientImgParams)) && 
ipsdk::imaproc::customImageProperty (_pOutRealImg,
 ipsdk::imaproc::fd::houghLines2dCheckOutImgSzYEquals (_pInGxGreyImg2d,_pInOptHoughLinesGradientImgParams)) && 
ipsdk::imaproc::matchSize (eMatchImageSizeType::eMIST_T,_pInGxGreyImg2d,_pOutRealImg) && 
ipsdk::imaproc::matchVolumeGeometryType (_pInGxGreyImg2d,_pOutRealImg) && 
ipsdk::imaproc::matchColorGeometryType (_pInGxGreyImg2d,_pOutRealImg) && 
ipsdk::imaproc::noInSitu (_pInGxGreyImg2d,_pOutRealImg)

Example of Python code :

Example imports

import PyIPSDK
import PyIPSDK.IPSDKIPLFeatureDetection as fd
import PyIPSDK.IPSDKIPLFiltering as filter

Code Example

    # opening of input image
    inImg = PyIPSDK.loadTiffImageFile(inputImgPath)
    
    # compute images of gradient along each axis, applying a gaussian gradient with
    # sigma=1
    gxImg, gyImg = filter.gaussianGradient2dImg(inImg, 1.0)
    
    # Initialize parameters for Hough lines accumulation matrix construction:
    # - step for rho = 1
    rhoStep = 2.0
    
    # - range of 15 evenly spaced orientations between pi/2 and 3.pi/4 radians
    thetaRange = PyIPSDK.createEvenlySpacedRange(math.pi/2, 3*math.pi/4, 15)
        
    # only accumulate pixels of input image with intensity greater than  70
    intensityThreshold = 70.0
    
    imgParams = PyIPSDK.createHoughLinesGradientImgParams(
        rhoStep, thetaRange, intensityThreshold)
        
    # orientation tolerance = 10 degrees (pi / 18 radians)
    orientationTolerance = math.pi/18
    
    # hough circle detection computation
    outImg = fd.houghLinesGradient2dImg(
        gxImg, gyImg, imgParams, orientationTolerance)

Example of C++ code :

Example informations

Associated library

IPSDKIPLFeatureDetection

Header file

#include <IPSDKIPL/IPSDKIPLFeatureDetection/Processor/HoughLinesGradient2dImg/HoughLinesGradient2dImg.h>

Code Example

    ImageConstPtr pInImg = loadTiffImageFile(inImgPath);

    GradientXYImg xyImg = sobelGradient2dImg(pInImg);

    // Initialize parameters for Hough lines accumulation matrix construction:
    // - step for rho = 1
    const ipReal64 rhoStep = 1.0;

    // - range of 15 evenly spaced orientations between pi/2 and 3.pi/4 radians
    const EvenlySpacedRange& thetaRange = *createEvenlySpacedRange(
        M_PI / 2, 3 * M_PI / 4, 15);

    // only accumulate pixels of input image with intensity greater than  10
    const ipReal32 intensityThreshold = 10.0f;
    const HoughLinesGradientImgParamsConstPtr pInHoughImgPrms =
        createHoughLinesGradientImgParams(
            rhoStep, thetaRange, intensityThreshold);

    // Initialize orientation tolerance parameter to 10 degrees (pi/18 radians)
    const ipReal32 orientationTolerance = static_cast<ipReal32>(M_PI / 18);

    // launch Hough lines detection algorithm
    const ImageConstPtr pOutImg = houghLinesGradient2dImg(
        xyImg._pXGradImg,
        xyImg._pYGradImg,
        pInHoughImgPrms,
        orientationTolerance);

See also

HoughLinesGradient2dImgLvl1

HoughLinesGradient2dImgLvl2

HoughLinesGradient2dImgLvl3

Function Documentation

houghLinesGradient2dImg() [1/2]

IPSDKIPLFEATUREDETECTION_API image::ImagePtr ipsdk::imaproc::fd::houghLinesGradient2dImg	(	const image::ImageConstPtr &	pInGxGreyImg2d,
		const image::ImageConstPtr &	pInGyGreyImg2d
	)

wrapper function for computation of accumulator matrix of extended Hough lines detector detector, from 2 images of gradient (one along x-axis, the other along y)

Exceptions

ipsdk::processor::IPSDKBaseProcessingException

on failure

houghLinesGradient2dImg() [2/2]

IPSDKIPLFEATUREDETECTION_API image::ImagePtr ipsdk::imaproc::fd::houghLinesGradient2dImg	(	const image::ImageConstPtr &	pInGxGreyImg2d,
		const image::ImageConstPtr &	pInGyGreyImg2d,
		const ipsdk::imaproc::attr::HoughLinesGradientImgParamsConstPtr &	pHoughLinesImgParams,
		const ipsdk::ipReal32	orientationTolerance
	)

wrapper function for computation of accumulator matrix of extended Hough lines detector detector, from 2 images of gradient (one along x-axis, the other along y)

Exceptions

ipsdk::processor::IPSDKBaseProcessingException

on failure