thresholdthresholdThresholdThresholdthreshold (Operator)

Name

thresholdthresholdThresholdThresholdthreshold — Segment an image using global threshold.

Signature

Description

thresholdthresholdThresholdThresholdThresholdthreshold 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 MinGrayMinGrayMinGrayMinGrayminGraymin_gray and MaxGrayMaxGrayMaxGrayMaxGraymaxGraymax_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 MinGrayMinGrayMinGrayMinGrayminGraymin_gray and MaxGrayMaxGrayMaxGrayMaxGraymaxGraymax_gray can be set to 'min'"min""min""min""min""min" or 'max'"max""max""max""max""max" in order to leave bottom and top limits, respectively, open.

Attention

The usage of MinGrayMinGrayMinGrayMinGrayminGraymin_gray and MaxGrayMaxGrayMaxGrayMaxGraymaxGraymax_gray can be affected by the input image type.

For images of type integer, floating point values in MinGrayMinGrayMinGrayMinGrayminGraymin_gray and MaxGrayMaxGrayMaxGrayMaxGraymaxGraymax_gray are truncated. For images of type real or vector field, floating point precision will be used for MinGrayMinGrayMinGrayMinGrayminGraymin_gray and MaxGrayMaxGrayMaxGrayMaxGraymaxGraymax_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);

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_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_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

thresholdthresholdThresholdThresholdThresholdthreshold returns 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""no_object_result", 'empty_region_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""store_empty_region" with set_systemset_systemSetSystemSetSystemSetSystemset_system. If necessary, an exception is raised.

Possible Predecessors

histo_to_threshhisto_to_threshHistoToThreshHistoToThreshHistoToThreshhisto_to_thresh, min_max_graymin_max_grayMinMaxGrayMinMaxGrayMinMaxGraymin_max_gray, sobel_ampsobel_ampSobelAmpSobelAmpSobelAmpsobel_amp, binomial_filterbinomial_filterBinomialFilterBinomialFilterBinomialFilterbinomial_filter, gauss_filtergauss_filterGaussFilterGaussFilterGaussFiltergauss_filter, reduce_domainreduce_domainReduceDomainReduceDomainReduceDomainreduce_domain, fill_interlacefill_interlaceFillInterlaceFillInterlaceFillInterlacefill_interlace

Possible Successors

connectionconnectionConnectionConnectionConnectionconnection, dilation1dilation1Dilation1Dilation1Dilation1dilation1, erosion1erosion1Erosion1Erosion1Erosion1erosion1, openingopeningOpeningOpeningOpeningopening, closingclosingClosingClosingClosingclosing, rank_regionrank_regionRankRegionRankRegionRankRegionrank_region, shape_transshape_transShapeTransShapeTransShapeTransshape_trans, skeletonskeletonSkeletonSkeletonSkeletonskeleton

Alternatives

class_2dim_supclass_2dim_supClass2dimSupClass2dimSupClass2dimSupclass_2dim_sup, hysteresis_thresholdhysteresis_thresholdHysteresisThresholdHysteresisThresholdHysteresisThresholdhysteresis_threshold, dyn_thresholddyn_thresholdDynThresholdDynThresholdDynThresholddyn_threshold, binary_thresholdbinary_thresholdBinaryThresholdBinaryThresholdBinaryThresholdbinary_threshold, char_thresholdchar_thresholdCharThresholdCharThresholdCharThresholdchar_threshold, auto_thresholdauto_thresholdAutoThresholdAutoThresholdAutoThresholdauto_threshold, dual_thresholddual_thresholdDualThresholdDualThresholdDualThresholddual_threshold

See also

zero_crossingzero_crossingZeroCrossingZeroCrossingZeroCrossingzero_crossing, background_segbackground_segBackgroundSegBackgroundSegBackgroundSegbackground_seg, regiongrowingregiongrowingRegiongrowingRegiongrowingRegiongrowingregiongrowing

Module

Foundation