Class NPPNativeMethods.NPPi.FilterHoughLine

Extracts Hough lines from a single channel 8-bit binarized (0, 255) source feature (canny edges, etc.) image and outputs a list of lines in point polar format representing the length(rho) and angle(theta) of each line from the origin of the normal to the line using the formula rho = x cos(theta) + y sin(theta). The level of discretization, nDelta, is specified as an input parameter.The performance and effectiveness of this function highly depends on this parameter with higher performance for larger numbers and more detailed results for lower numbers. Also, lines are not guaranteed to be added to the pDeviceLines list in the same order from one call to the next. However, all of the same lines will still be generated as long as nMaxLineCount is set large enough so that they all can fit in the list. To convert lines in point polar format back to cartesian lines use the following formula:

Inheritance

System.Object

NPPNativeMethods.NPPi.FilterHoughLine

Inherited Members

System.Object.Equals(System.Object)

System.Object.Equals(System.Object, System.Object)

System.Object.GetHashCode()

System.Object.GetType()

System.Object.MemberwiseClone()

System.Object.ReferenceEquals(System.Object, System.Object)

System.Object.ToString()

Namespace: ManagedCuda.NPP

Assembly: NPP.dll

Syntax

public static class FilterHoughLine

Methods

nppiFilterHoughLine_8u32f_C1R(CUdeviceptr, Int32, NppiSize, NppPointPolar, Int32, CUdeviceptr, Int32, CUdeviceptr, CUdeviceptr)

1 channel 8-bit unsigned binarized (0, 255) source feature (canny edges, etc.) source image to list of lines in point polar format representing the length (rho) and angle (theta) of each line from the origin of the normal to the line using the formula rho = x cos(theta) + y sin(theta). The level of discretization, nDelta, is specified as an input parameter. The performance and effectiveness of this function highly depends on this parameter with higher performance for larger numbers and more detailed results for lower numbers. nDelta must have the same values as those used in the nppiFilterHoughLineGetBufferSize() function call.

Declaration

public static NppStatus nppiFilterHoughLine_8u32f_C1R(CUdeviceptr pSrc, int nSrcStep, NppiSize oSizeROI, NppPointPolar nDelta, int nThreshold, CUdeviceptr pDeviceLines, int nMaxLineCount, CUdeviceptr pDeviceLineCount, CUdeviceptr pDeviceBuffer)

Parameters

Type	Name	Description
CUdeviceptr	pSrc	Source-Image Pointer.
System.Int32	nSrcStep	Source-Image Line Step.
NppiSize	oSizeROI	Region-of-Interest (ROI).
NppPointPolar	nDelta	Discretization steps, range 0.0F < radial increment nDelta.rho < 3.0F, 1.0F recommended, range 0.25F < angular increment nDelta.theta < 3.0F, 1.0F recommended.
System.Int32	nThreshold	Minimum number of points to accept a line.
CUdeviceptr	pDeviceLines	Device pointer to (nMaxLineCount * sizeof(NppPointPolar) line objects.
System.Int32	nMaxLineCount	The maximum number of lines to output.
CUdeviceptr	pDeviceLineCount	The number of lines detected by this function up to nMaxLineCount.
CUdeviceptr	pDeviceBuffer	pointer to scratch DEVICE memory buffer of size hpBufferSize (see nppiFilterHoughLineGetBufferSize() above)

Returns

Type	Description
NppStatus

nppiFilterHoughLineGetBufferSize(NppiSize, NppPointPolar, Int32, ref Int32)

Calculate scratch buffer size needed for the FilterHoughLine or FilterHoughLineRegion functions based on destination image SizeROI width and height and nDelta parameters.

Declaration

public static NppStatus nppiFilterHoughLineGetBufferSize(NppiSize oSizeROI, NppPointPolar nDelta, int nMaxLineCount, ref int hpBufferSize)

Parameters

Type	Name	Description
NppiSize	oSizeROI	Region-of-Interest (ROI).
NppPointPolar	nDelta	rho radial increment and theta angular increment that will be used in the FilterHoughLine or FilterHoughLineRegion function call.
System.Int32	nMaxLineCount	The maximum number of lines expected from the FilterHoughLine or FilterHoughLineRegion function call.
System.Int32	hpBufferSize	Required buffer size in bytes. Important: hpBufferSize is a

Returns

Type	Description
NppStatus

nppiFilterHoughLineRegion_8u32f_C1R(CUdeviceptr, Int32, NppiSize, NppPointPolar, Int32, CUdeviceptr, NppPointPolar[], Int32, CUdeviceptr, CUdeviceptr)

Declaration

public static NppStatus nppiFilterHoughLineRegion_8u32f_C1R(CUdeviceptr pSrc, int nSrcStep, NppiSize oSizeROI, NppPointPolar nDelta, int nThreshold, CUdeviceptr pDeviceLines, NppPointPolar[] oDstROI, int nMaxLineCount, CUdeviceptr pDeviceLineCount, CUdeviceptr pDeviceBuffer)

Parameters

Type	Name	Description
CUdeviceptr	pSrc	Source-Image Pointer.
System.Int32	nSrcStep	Source-Image Line Step.
NppiSize	oSizeROI	Region-of-Interest (ROI).
NppPointPolar	nDelta	Discretization steps, range 0.0F < radial increment nDelta.rho < 3.0F, 1.0F recommended, range 0.25F < angular increment nDelta.theta < 3.0F, 1.0F recommended.
System.Int32	nThreshold	Minimum number of points to accept a line.
CUdeviceptr	pDeviceLines	Device pointer to (nMaxLineCount * sizeof(NppPointPolar) line objects.
NppPointPolar[]	oDstROI	Region limits with oDstROI[0].rho <= accepted rho <= oDstROI[1].rho and oDstROI[0].theta <= accepted theta <= oDstROI[1].theta.
System.Int32	nMaxLineCount	The maximum number of lines to output.
CUdeviceptr	pDeviceLineCount	The number of lines detected by this function up to nMaxLineCount.
CUdeviceptr	pDeviceBuffer	pointer to scratch DEVICE memory buffer of size hpBufferSize (see nppiFilterHoughLineGetBufferSize() above)

Returns

Type	Description
NppStatus