derivate_gaussderivate_gaussDerivateGaussDerivateGauss (Operator)

Name

derivate_gaussderivate_gaussDerivateGaussDerivateGauss — Convolve an image with derivatives of the Gaussian.

Signature

Description

derivate_gaussderivate_gaussDerivateGaussDerivateGaussDerivateGauss convolves an image with the derivatives of a Gaussian and calculates various features derived therefrom. SigmaSigmaSigmaSigmasigma is the parameter of the Gaussian (i.e., the amount of smoothing). If one value is passed in SigmaSigmaSigmaSigmasigma the amount of smoothing in the column and row direction is identical. If two values are passed in SigmaSigmaSigmaSigmasigma the first value specifies the amount of smoothing in the column direction, while the second value specifies the amount of smoothing in the row direction. The possible values for ComponentComponentComponentComponentcomponent are:

'none'"none""none""none""none":

Smoothing only.

'x'"x""x""x""x":

First derivative along x.

'y'"y""y""y""y":

First derivative along y.

'gradient'"gradient""gradient""gradient""gradient":

Absolute value of the gradient.

'gradient_dir'"gradient_dir""gradient_dir""gradient_dir""gradient_dir":

Gradient direction in radians.

'xx'"xx""xx""xx""xx":

Second derivative along x.

'yy'"yy""yy""yy""yy":

Second derivative along y.

'xy'"xy""xy""xy""xy":

Second derivative along x and y.

'xxx'"xxx""xxx""xxx""xxx":

Third derivative along x.

'yyy'"yyy""yyy""yyy""yyy":

Third derivative along y.

'xxy'"xxy""xxy""xxy""xxy":

Third derivative along x, x and y.

'xyy'"xyy""xyy""xyy""xyy":

Third derivative along x, y and y.

'det'"det""det""det""det":

Determinant of the Hessian matrix:

'laplace'"laplace""laplace""laplace""laplace":

Laplace operator (trace of the Hessian matrix):

'mean_curvature'"mean_curvature""mean_curvature""mean_curvature""mean_curvature":

Mean curvature H

'gauss_curvature'"gauss_curvature""gauss_curvature""gauss_curvature""gauss_curvature":

Gaussian curvature K

'area'"area""area""area""area":

Differential Area A

'eigenvalue1'"eigenvalue1""eigenvalue1""eigenvalue1""eigenvalue1":

First eigenvalue

'eigenvalue2'"eigenvalue2""eigenvalue2""eigenvalue2""eigenvalue2":

Second eigenvalue

'eigenvec_dir'"eigenvec_dir""eigenvec_dir""eigenvec_dir""eigenvec_dir":

Direction of the eigenvector corresponding to the first eigenvalue in radians

'kitchen_rosenfeld'"kitchen_rosenfeld""kitchen_rosenfeld""kitchen_rosenfeld""kitchen_rosenfeld":

Second derivative perpendicular to the gradient

'zuniga_haralick'"zuniga_haralick""zuniga_haralick""zuniga_haralick""zuniga_haralick":

Normalized second derivative perpendicular to the gradient

'2nd_ddg'"2nd_ddg""2nd_ddg""2nd_ddg""2nd_ddg":

Second derivative along the gradient

'de_saint_venant'"de_saint_venant""de_saint_venant""de_saint_venant""de_saint_venant":

Second derivative along and perpendicular to the gradient

Attention

derivate_gaussderivate_gaussDerivateGaussDerivateGaussDerivateGauss uses a special implementation that is optimized using SSE2 instructions if the system parameter 'sse2_enable'"sse2_enable""sse2_enable""sse2_enable""sse2_enable" is set to 'true'"true""true""true""true" (which is default if SSE2 is available on your machine). This implementation is slightly inaccurate compared to the pure C version due to numerical issues (for 'byte' images and ComponentComponentComponentComponentcomponent 'none'"none""none""none""none", 'x'"x""x""x""x", or 'y'"y""y""y""y" the difference is in order of magnitude of 1.0e-5). If you prefer accuracy over performance you can set 'sse2_enable'"sse2_enable""sse2_enable""sse2_enable""sse2_enable" to 'false'"false""false""false""false" (using set_systemset_systemSetSystemSetSystemSetSystem) before you call derivate_gaussderivate_gaussDerivateGaussDerivateGaussDerivateGauss. This way derivate_gaussderivate_gaussDerivateGaussDerivateGaussDerivateGauss does not use SSE2 accelerations. Don't forget to set 'sse2_enable'"sse2_enable""sse2_enable""sse2_enable""sse2_enable" back to 'true'"true""true""true""true" afterwards.

derivate_gaussderivate_gaussDerivateGaussDerivateGaussDerivateGauss is only executed on an OpenCL device if SigmaSigmaSigmaSigmasigma induces a filter width respectively height of up to 129 pixels. This corresponds to a SigmaSigmaSigmaSigmasigma of less than 20.7 for ComponentComponentComponentComponentcomponent = 'none'"none""none""none""none". Further as the SSE2 version the OpenCL implementation is slightly inaccurate compared to the pure C version due to numerical issues.

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

• Supports OpenCL compute devices.
• 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

Example (C)

read_image(&Image,"mreut");
derivate_gauss(Image,&Gauss,3.0,"x");
zero_crossing(Gauss,&ZeroCrossings);

Possible Successors

zero_crossingzero_crossingZeroCrossingZeroCrossingZeroCrossing, dual_thresholddual_thresholdDualThresholdDualThresholdDualThreshold

Alternatives

laplacelaplaceLaplaceLaplaceLaplace, laplace_of_gausslaplace_of_gaussLaplaceOfGaussLaplaceOfGaussLaplaceOfGauss, binomial_filterbinomial_filterBinomialFilterBinomialFilterBinomialFilter, gauss_filtergauss_filterGaussFilterGaussFilterGaussFilter, smooth_imagesmooth_imageSmoothImageSmoothImageSmoothImage, isotropic_diffusionisotropic_diffusionIsotropicDiffusionIsotropicDiffusionIsotropicDiffusion

See also

zero_crossingzero_crossingZeroCrossingZeroCrossingZeroCrossing, dual_thresholddual_thresholdDualThresholdDualThresholdDualThreshold

Module

Foundation