symmetrysymmetrySymmetrySymmetry (Operator)

Name

symmetrysymmetrySymmetrySymmetry — Symmetry of gray values along a row.

Signature

symmetry(Image : ImageSymmetry : MaskSize, Direction, Exponent : )

symmetrysymmetrySymmetrySymmetrySymmetry calculates the symmetry along a line. For each pixel the gray values of both sides of the line are compared: The absolute value of the differences of gray values with same distance to the pixel is computed. Each of these differences is weighted by the exponent (after division by 255) and then summed up.

Pixels with a high symmetry have large gray values.

Attention

Currently only horizontal search lines are implemented. Note that the parameter DirectionDirectionDirectionDirectiondirection exists for future extensions and can currently only have the value 0.0.

Note that filter operators may return unexpected results if an image with a reduced domain is used as input. Please refer to the chapter Filters.

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 channel level.
Automatically parallelized on domain level.

Parameters

ImageImageImageImageimage (input_object) (multichannel-)image(-array) → object (byte)

Input image.

ImageSymmetryImageSymmetryImageSymmetryImageSymmetryimageSymmetry (output_object) (multichannel-)image(-array) → object (byte)

Symmetry image.

MaskSizeMaskSizeMaskSizeMaskSizemaskSize (input_control) number → (integer)

Extension of search area.

Default value: 40

Suggested values: 3, 5, 7, 10, 15, 20, 25, 30, 40, 50, 60, 70, 80, 100, 120, 140, 180

Typical range of values: 3 ≤ MaskSize MaskSize MaskSize MaskSize maskSize ≤ 1000

Minimum increment: 1

Recommended increment: 2

DirectionDirectionDirectionDirectiondirection (input_control) number → (real)

Angle of test direction.

Default value: 0.0

Suggested values: 0.0

Typical range of values: 0.0 ≤ Direction Direction Direction Direction direction ≤ 0.0

ExponentExponentExponentExponentexponent (input_control) number → (real)

Exponent for weighting.

Default value: 0.5

Suggested values: 0.1, 0.2, 0.3, 0.4, 0.5, 0.7, 0.8, 0.9, 1.0

Typical range of values: 0.05 ≤ Exponent Exponent Exponent Exponent exponent ≤ 1.0

Minimum increment: 0.01

Recommended increment: 0.1

Restriction: 0 < Exponent && Exponent <= 1

Example (HDevelop)

read_image(Image,'monkey')
symmetry(Image,ImageSymmetry,70,0.0,0.5)
threshold(ImageSymmetry,SymmPoints,170,255)

Result

If the parameter values are correct the operator symmetrysymmetrySymmetrySymmetrySymmetry returns the value 2 (H_MSG_TRUE) The behavior in case of empty input (no input images available) is set via the operator set_system(::'no_object_result',<Result>:)set_system("no_object_result",<Result>)SetSystem("no_object_result",<Result>)SetSystem("no_object_result",<Result>)SetSystem("no_object_result",<Result>). If necessary an exception is raised.

Possible Successors

thresholdthresholdThresholdThresholdThreshold

Module

Foundation

Operators