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prewitt_dirprewitt_dirPrewittDirprewitt_dirPrewittDirPrewittDir (Operator)

Name

prewitt_dirprewitt_dirPrewittDirprewitt_dirPrewittDirPrewittDir — Detect edges (amplitude and direction) using the Prewitt operator.

Signature

prewitt_dir(Image : ImageEdgeAmp, ImageEdgeDir : : )

Herror prewitt_dir(const Hobject Image, Hobject* ImageEdgeAmp, Hobject* ImageEdgeDir)

Herror T_prewitt_dir(const Hobject Image, Hobject* ImageEdgeAmp, Hobject* ImageEdgeDir)

Herror prewitt_dir(Hobject Image, Hobject* ImageEdgeAmp, Hobject* ImageEdgeDir)

HImage HImage::PrewittDir(HImage* ImageEdgeDir) const

HImageArray HImageArray::PrewittDir(HImageArray* ImageEdgeDir) const

void PrewittDir(const HObject& Image, HObject* ImageEdgeAmp, HObject* ImageEdgeDir)

HImage HImage::PrewittDir(HImage* ImageEdgeDir) const

void HOperatorSetX.PrewittDir(
[in] IHUntypedObjectX* Image, [out] IHUntypedObjectX** ImageEdgeAmp, [out] IHUntypedObjectX** ImageEdgeDir)

IHImageX* HImageX.PrewittDir([out] IHImageX** ImageEdgeDir)

static void HOperatorSet.PrewittDir(HObject image, out HObject imageEdgeAmp, out HObject imageEdgeDir)

HImage HImage.PrewittDir(out HImage imageEdgeDir)

Description

prewitt_dirprewitt_dirPrewittDirprewitt_dirPrewittDirPrewittDir calculates an approximation of the first derivative of the image data and is used as an edge detector. The filter is based on the following filter masks: 

  A =
        1       1       1
        0       0       0
       -1      -1      -1

  B =
        1       0      -1
        1       0      -1
        1       0      -1
The result image contains the maximum response of the masks A and B. The edge directions are returned in ImageEdgeDirImageEdgeDirImageEdgeDirImageEdgeDirImageEdgeDirimageEdgeDir, and are stored in 2-degree steps, i.e., an edge direction of x degrees mathematically positive sense and with respect to the horizontal axis is stored as x / 2 in the edge direction image. Furthermore, the direction of the change of intensity is taken into account. Let denote the image gradient. Then the following edge directions are returned as r/2:
Points with edge amplitude 0 are assigned the edge direction 255 (undefined direction).

Parallelization

Parameters

ImageImageImageImageImageimage (input_object)  (multichannel-)image(-array) → objectHImageHImageHImageHImageXHobject (byte / int2 / uint2)

Input image.

ImageEdgeAmpImageEdgeAmpImageEdgeAmpImageEdgeAmpImageEdgeAmpimageEdgeAmp (output_object)  (multichannel-)image(-array) → objectHImageHImageHImageHImageXHobject * (byte / int2 / uint2)

Edge amplitude (gradient magnitude) image.

ImageEdgeDirImageEdgeDirImageEdgeDirImageEdgeDirImageEdgeDirimageEdgeDir (output_object)  (multichannel-)image(-array) → objectHImageHImageHImageHImageXHobject * (direction)

Edge direction image.

Example (HDevelop)

read_image(Image,'fabrik')
prewitt_dir(Image,PrewittA,PrewittD)
threshold(PrewittA,Edges,128,255)

Example (C)

read_image(&Image,"fabrik");
prewitt_dir(Image,&PrewittA,&PrewittD);
threshold(PrewittA,&Edges,128,255);

Example (HDevelop)

read_image(Image,'fabrik')
prewitt_dir(Image,PrewittA,PrewittD)
threshold(PrewittA,Edges,128,255)

Example (HDevelop)

read_image(Image,'fabrik')
prewitt_dir(Image,PrewittA,PrewittD)
threshold(PrewittA,Edges,128,255)

Example (HDevelop)

read_image(Image,'fabrik')
prewitt_dir(Image,PrewittA,PrewittD)
threshold(PrewittA,Edges,128,255)

Example (HDevelop)

read_image(Image,'fabrik')
prewitt_dir(Image,PrewittA,PrewittD)
threshold(PrewittA,Edges,128,255)

Result

prewitt_dirprewitt_dirPrewittDirprewitt_dirPrewittDirPrewittDir always returns 2 (H_MSG_TRUE). If the input is empty the behaviour can be set via set_system('no_object_result',<Result>)set_system("no_object_result",<Result>)SetSystem("no_object_result",<Result>)set_system("no_object_result",<Result>)SetSystem("no_object_result",<Result>)SetSystem("no_object_result",<Result>). If necessary, an exception is raised.

Possible Predecessors

binomial_filterbinomial_filterBinomialFilterbinomial_filterBinomialFilterBinomialFilter, gauss_filtergauss_filterGaussFiltergauss_filterGaussFilterGaussFilter, sigma_imagesigma_imageSigmaImagesigma_imageSigmaImageSigmaImage, median_imagemedian_imageMedianImagemedian_imageMedianImageMedianImage, smooth_imagesmooth_imageSmoothImagesmooth_imageSmoothImageSmoothImage

Possible Successors

hysteresis_thresholdhysteresis_thresholdHysteresisThresholdhysteresis_thresholdHysteresisThresholdHysteresisThreshold, thresholdthresholdThresholdthresholdThresholdThreshold, gray_skeletongray_skeletonGraySkeletongray_skeletonGraySkeletonGraySkeleton, nonmax_suppression_dirnonmax_suppression_dirNonmaxSuppressionDirnonmax_suppression_dirNonmaxSuppressionDirNonmaxSuppressionDir, close_edgesclose_edgesCloseEdgesclose_edgesCloseEdgesCloseEdges, close_edges_lengthclose_edges_lengthCloseEdgesLengthclose_edges_lengthCloseEdgesLengthCloseEdgesLength

Alternatives

edges_imageedges_imageEdgesImageedges_imageEdgesImageEdgesImage, sobel_dirsobel_dirSobelDirsobel_dirSobelDirSobelDir, robinson_dirrobinson_dirRobinsonDirrobinson_dirRobinsonDirRobinsonDir, frei_dirfrei_dirFreiDirfrei_dirFreiDirFreiDir, kirsch_dirkirsch_dirKirschDirkirsch_dirKirschDirKirschDir

See also

bandpass_imagebandpass_imageBandpassImagebandpass_imageBandpassImageBandpassImage, laplace_of_gausslaplace_of_gaussLaplaceOfGausslaplace_of_gaussLaplaceOfGaussLaplaceOfGauss

Module

Foundation

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HALCON Operator Reference 12.0.2 Copyright © 1996-2016 MVTec Software GmbH