threshold_sub_pixthreshold_sub_pixthreshold_sub_pixThresholdSubPixThresholdSubPix (Operator)

Name

threshold_sub_pixthreshold_sub_pixthreshold_sub_pixThresholdSubPixThresholdSubPix — Extract level crossings from an image with subpixel accuracy.

Signature

Description

threshold_sub_pixthreshold_sub_pixthreshold_sub_pixThresholdSubPixThresholdSubPix extracts the level crossings at the level ThresholdThresholdThresholdThresholdthreshold of the input image ImageImageImageImageimage with subpixel accuracy. The extracted level crossings are returned as XLD-contours in BorderBorderBorderBorderborder. In contrast to the operator thresholdthresholdthresholdThresholdThreshold, threshold_sub_pixthreshold_sub_pixthreshold_sub_pixThresholdSubPixThresholdSubPix does not return regions, but the lines that separate regions with a gray value less than ThresholdThresholdThresholdThresholdthreshold from regions with a gray value greater than ThresholdThresholdThresholdThresholdthreshold.

For the extraction, the input image is regarded as a surface, in which the gray values are interpolated bilinearly between the centers of the individual pixels. Consistent with the surface thus defined, level crossing lines are extracted for each pixel and linked into topologically sound contours. This means that the level crossing contours are correctly split at junction points. If the image contains extended areas of constant gray value ThresholdThresholdThresholdThresholdthreshold, only the border of such areas is returned as level crossings.

Parallelization

• Multithreading type: reentrant (runs in parallel with non-exclusive operators).
• Multithreading scope: global (may be called from any thread).
• Processed without parallelization.

Parameters

read_image(Image,'fabrik')
threshold_sub_pix(Image,Border,35)
disp_xld(Border,WindowHandle)

/* Detection zero crossings of the Laplacian-of-Gaussian of aerial image */
read_image(&Image,"fabrik");
threshold_sub_pix(Laplace,&Border,35);
disp_xld(Border,WindowHandle);

/* Detection zero crossings of the Laplacian-of-Gaussian of aerial image */
HWindow Window(0,0,512,512);
HImage Image("fabrik");
HXLDContArray Border = Image.ThresholdSubPix(35);
Border.Display(Window);

read_image(Image,'fabrik')
threshold_sub_pix(Image,Border,35)
disp_xld(Border,WindowHandle)

read_image(Image,'fabrik')
threshold_sub_pix(Image,Border,35)
disp_xld(Border,WindowHandle)

Result

threshold_sub_pixthreshold_sub_pixthreshold_sub_pixThresholdSubPixThresholdSubPix usually returns the value 2 (H_MSG_TRUE). If necessary, an exception is raised.

Alternatives

thresholdthresholdthresholdThresholdThreshold

See also

zero_crossing_sub_pixzero_crossing_sub_pixzero_crossing_sub_pixZeroCrossingSubPixZeroCrossingSubPix

Module

2D Metrology