thresholdthresholdThresholdThresholdthreshold (Operator)

Name

thresholdthresholdThresholdThresholdthreshold — Segment an image using global threshold.

Signature

Description

thresholdthresholdThresholdThresholdthreshold selects the pixels from the input image whose gray values g fulfill the following condition:

All points of an image fulfilling the condition are returned as one region. If more than one gray value interval is passed (tuples for MinGrayMinGrayMinGrayminGraymin_gray and MaxGrayMaxGrayMaxGraymaxGraymax_gray), one separate region is returned for each interval. For vector field images, the threshold is not applied to gray values but to the lengths of the vectors. The parameters MinGrayMinGrayMinGrayminGraymin_gray and MaxGrayMaxGrayMaxGraymaxGraymax_gray can be set to 'min'"min""min""min""min" or 'max'"max""max""max""max" in order to leave bottom and top limits, respectively, open.

Attention

The usage of MinGrayMinGrayMinGrayminGraymin_gray and MaxGrayMaxGrayMaxGraymaxGraymax_gray can be affected by the input image type.

For images of type integer, floating point values in MinGrayMinGrayMinGrayminGraymin_gray and MaxGrayMaxGrayMaxGraymaxGraymax_gray are truncated. For images of type real or vector field, floating point precision will be used for MinGrayMinGrayMinGrayminGraymin_gray and MaxGrayMaxGrayMaxGraymaxGraymax_gray, if they are of type double.

Execution Information

• Multithreading type: reentrant (runs in parallel with non-exclusive operators).
• Multithreading scope: global (may be called from any thread).
• Automatically parallelized on tuple level.
• Automatically parallelized on internal data level.

Parameters

read_image(Image,'fabrik')
sobel_dir(Image,EdgeAmp,EdgeDir,'sum_abs',3)
threshold(EdgeAmp,Seg,50,255)
skeleton(Seg,Rand)
connection(Rand,Lines)
select_shape(Lines,Edges,'area','and',10,1000000)

read_image(&Image,"fabrik");
sobel_amp(Image,&EdgeAmp,"sum_abs",3);
threshold(EdgeAmp,&Seg,50.0,255.0);
skeleton(Seg,&Rand);
connection(Rand,&Lines);
select_shape(Lines,&Edges,"area","and",10.0,1000000.0);

#include "HIOStream.h"
#if !defined(USE_IOSTREAM_H)
using namespace std;
#endif
#include "HalconCpp.h"
using namespace Halcon;

int main (int argc, char *argv[])
{
  if (argc != 4)
  {
    cout << "Usage : " << argv[0] << " 'image' MinGray MaxGray" << endl;
    return (-1);
  }

  HImage   image (argv[1]),
           Sobel;
  HWindow  win;

  image.Display (win);

  int MinGray = atoi (argv[2]);
  int MaxGray = atoi (argv[3]);

  Sobel = image.SobelAmp ("sum_abs", 3);

  HRegionArray rand  = ((image >= MinGray) & (image <= MaxGray)).Skeleton();
  HRegionArray lines = rand.Connection();
  HRegionArray edges = lines.SelectShape("area", "and", 10.0, 10000000.0);

  edges.Display (win);
  win.Click ();

  return (0);
}

read_image(Image,'fabrik')
sobel_dir(Image,EdgeAmp,EdgeDir,'sum_abs',3)
threshold(EdgeAmp,Seg,50,255)
skeleton(Seg,Rand)
connection(Rand,Lines)
select_shape(Lines,Edges,'area','and',10,1000000)

Complexity

Let A be the area of the input region. Then the runtime complexity is O(A).

Result

thresholdthresholdThresholdThresholdthreshold returns 2 ( H_MSG_TRUE) if all parameters are correct. The behavior with respect to the input images and output regions can be determined by setting the values of the flags 'no_object_result'"no_object_result""no_object_result""no_object_result""no_object_result", 'empty_region_result'"empty_region_result""empty_region_result""empty_region_result""empty_region_result", and 'store_empty_region'"store_empty_region""store_empty_region""store_empty_region""store_empty_region" with set_systemset_systemSetSystemSetSystemset_system. If necessary, an exception is raised.

Possible Predecessors

histo_to_threshhisto_to_threshHistoToThreshHistoToThreshhisto_to_thresh, min_max_graymin_max_grayMinMaxGrayMinMaxGraymin_max_gray, sobel_ampsobel_ampSobelAmpSobelAmpsobel_amp, binomial_filterbinomial_filterBinomialFilterBinomialFilterbinomial_filter, gauss_filtergauss_filterGaussFilterGaussFiltergauss_filter, reduce_domainreduce_domainReduceDomainReduceDomainreduce_domain, fill_interlacefill_interlaceFillInterlaceFillInterlacefill_interlace

Possible Successors

connectionconnectionConnectionConnectionconnection, dilation1dilation1Dilation1Dilation1dilation1, erosion1erosion1Erosion1Erosion1erosion1, openingopeningOpeningOpeningopening, closingclosingClosingClosingclosing, rank_regionrank_regionRankRegionRankRegionrank_region, shape_transshape_transShapeTransShapeTransshape_trans, skeletonskeletonSkeletonSkeletonskeleton

Alternatives

class_2dim_supclass_2dim_supClass2dimSupClass2dimSupclass_2dim_sup, hysteresis_thresholdhysteresis_thresholdHysteresisThresholdHysteresisThresholdhysteresis_threshold, dyn_thresholddyn_thresholdDynThresholdDynThresholddyn_threshold, binary_thresholdbinary_thresholdBinaryThresholdBinaryThresholdbinary_threshold, char_thresholdchar_thresholdCharThresholdCharThresholdchar_threshold, auto_thresholdauto_thresholdAutoThresholdAutoThresholdauto_threshold, dual_thresholddual_thresholdDualThresholdDualThresholddual_threshold

See also

zero_crossingzero_crossingZeroCrossingZeroCrossingzero_crossing, background_segbackground_segBackgroundSegBackgroundSegbackground_seg, regiongrowingregiongrowingRegiongrowingRegiongrowingregiongrowing

Module

Foundation