auto_thresholdauto_thresholdAutoThresholdAutoThresholdauto_threshold (Operator)

Name

auto_thresholdauto_thresholdAutoThresholdAutoThresholdauto_threshold — Segment an image using thresholds determined from its histogram.

Signature

Description

auto_thresholdauto_thresholdAutoThresholdAutoThresholdAutoThresholdauto_threshold segments a single-channel image using multiple thresholding. First, the absolute histogram of the gray values is determined. Then, relevant minima are extracted from the histogram, which are used successively as parameters for a thresholding operation. The thresholds used for byte images are 0, 255, and all minima extracted from the histogram (after the histogram has been smoothed with a Gaussian filter with standard deviation SigmaSigmaSigmaSigmasigmasigma). For each gray value interval one region is generated. Thus, the number of regions is the number of minima + 1. For uint2 images, the above procedure is used analogously. However, here the highest threshold is 65535. Furthermore, for uint2 images the value of SigmaSigmaSigmaSigmasigmasigma (virtually) refers to a histogram with 256 values, although internally histograms with a higher resolution are used. This is done to facilitate switching between image types without having to change the parameter SigmaSigmaSigmaSigmasigmasigma. For float images the thresholds are the minimum and maximum gray value in the image and all minima extracted from the histogram. Here, the scaling of the parameter SigmaSigmaSigmaSigmasigmasigma refers to the original gray values of the image. The larger the value of SigmaSigmaSigmaSigmasigmasigma is chosen, the fewer regions will be extracted. This operator is useful if the regions to be extracted exhibit similar gray values (homogeneous regions).

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')
median_image (Image, Median, 'circle', 3, 'mirrored')
auto_threshold (Median, Seg, 2.0)
connection (Seg, Connected)

read_image(&Image,"fabrik");
median_image(Image,&Median,"circle",3,"mirrored");
auto_threshold(Median,&Seg,2.0);
connection(Seg,&Connected);
set_colored(WindowHandle,12);
disp_obj(Connected,WindowHandle);

read_image (Image, 'fabrik')
median_image (Image, Median, 'circle', 3, 'mirrored')
auto_threshold (Median, Seg, 2.0)
connection (Seg, Connected)

read_image (Image, 'fabrik')
median_image (Image, Median, 'circle', 3, 'mirrored')
auto_threshold (Median, Seg, 2.0)
connection (Seg, Connected)

read_image (Image, 'fabrik')
median_image (Image, Median, 'circle', 3, 'mirrored')
auto_threshold (Median, Seg, 2.0)
connection (Seg, Connected)

Possible Predecessors

anisotropic_diffusionanisotropic_diffusionAnisotropicDiffusionAnisotropicDiffusionAnisotropicDiffusionanisotropic_diffusion, median_imagemedian_imageMedianImageMedianImageMedianImagemedian_image, illuminateilluminateIlluminateIlluminateIlluminateilluminate

Possible Successors

connectionconnectionConnectionConnectionConnectionconnection, select_shapeselect_shapeSelectShapeSelectShapeSelectShapeselect_shape, select_grayselect_graySelectGraySelectGraySelectGrayselect_gray

Alternatives

binary_thresholdbinary_thresholdBinaryThresholdBinaryThresholdBinaryThresholdbinary_threshold, char_thresholdchar_thresholdCharThresholdCharThresholdCharThresholdchar_threshold

See also

gray_histogray_histoGrayHistoGrayHistoGrayHistogray_histo, gray_histo_absgray_histo_absGrayHistoAbsGrayHistoAbsGrayHistoAbsgray_histo_abs, histo_to_threshhisto_to_threshHistoToThreshHistoToThreshHistoToThreshhisto_to_thresh, smooth_funct_1d_gausssmooth_funct_1d_gaussSmoothFunct1dGaussSmoothFunct1dGaussSmoothFunct1dGausssmooth_funct_1d_gauss, thresholdthresholdThresholdThresholdThresholdthreshold

Module

Foundation