smooth_imagesmooth_imagesmooth_imageSmoothImageSmoothImage (Operator)

Name

smooth_imagesmooth_imagesmooth_imageSmoothImageSmoothImage — Smooth an image using recursive filters.

Signature

Description

smooth_imagesmooth_imagesmooth_imageSmoothImageSmoothImage smooths gray images using recursive filters originally developed by Deriche and Shen and using the non-recursive Gaussian filter. The following filters can be choosen via the parameter FilterFilterFilterFilterfilter:

             'deriche1', 'deriche2', 'shen' and 'gauss'.

The “filter width” (i.e., the range of the filter and thereby result of the filter) can be of any size. In the case that the Deriche or Shen is choosen it decreases by increasing the filter parameter AlphaAlphaAlphaAlphaalpha and increases in the case of the Gauss filter (and AlphaAlphaAlphaAlphaalpha corresponds to the standard deviation of the Gaussian function). An approximation of the appropiate size of the filterwidth AlphaAlphaAlphaAlphaalpha is performed by the operator info_smoothinfo_smoothinfo_smoothInfoSmoothInfoSmooth.

Non-recursive filters like the Gaussian filter are often implemented using filter-masks. In this case the runtime of the operator increases with increasing size of the filter mask. The runtime of the recursive filters remains constant; except the border treatment becomes a little bit more time consuming. The Gaussian filter becomes slow in comparison to the recursive ones but is in contrast to them isotropic (the filter 'deriche2' is only weakly direction sensitive). A comparable result of the smoothing is achieved by choosing the following values for the parameter:

            Alpha(deriche2) = Alpha(deriche1) / 2,
            Alpha(shen)     = Alpha(deriche1) / 2,
            Alpha(gauss)    = 1.77 / Alpha(deriche1).

Parallelization

• 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 internal data level.

Parameters

info_smooth('deriche2',0.5,Size,Coeffs)
smooth_image(Input,Smooth,'deriche2',7)

info_smooth('deriche2',0.5,Size,Coeffs);
smooth_image(Input,&Smooth,'deriche2',7);

info_smooth('deriche2',0.5,Size,Coeffs)
smooth_image(Input,Smooth,'deriche2',7)

info_smooth('deriche2',0.5,Size,Coeffs)
smooth_image(Input,Smooth,'deriche2',7)

info_smooth('deriche2',0.5,Size,Coeffs)
smooth_image(Input,Smooth,'deriche2',7)

Result

If the parameter values are correct the operator smooth_imagesmooth_imagesmooth_imageSmoothImageSmoothImage 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>)set_system("no_object_result",<Result>)SetSystem("no_object_result",<Result>)SetSystem("no_object_result",<Result>). If necessary an exception is raised.

Possible Predecessors

read_imageread_imageread_imageReadImageReadImage

Possible Successors

thresholdthresholdthresholdThresholdThreshold, dyn_thresholddyn_thresholddyn_thresholdDynThresholdDynThreshold, regiongrowingregiongrowingregiongrowingRegiongrowingRegiongrowing

Alternatives

binomial_filterbinomial_filterbinomial_filterBinomialFilterBinomialFilter, gauss_imagegauss_imagegauss_imageGaussImageGaussImage, mean_imagemean_imagemean_imageMeanImageMeanImage, derivate_gaussderivate_gaussderivate_gaussDerivateGaussDerivateGauss, isotropic_diffusionisotropic_diffusionisotropic_diffusionIsotropicDiffusionIsotropicDiffusion

See also

info_smoothinfo_smoothinfo_smoothInfoSmoothInfoSmooth, median_imagemedian_imagemedian_imageMedianImageMedianImage, sigma_imagesigma_imagesigma_imageSigmaImageSigmaImage, anisotropic_diffusionanisotropic_diffusionanisotropic_diffusionAnisotropicDiffusionAnisotropicDiffusion

References

R.Deriche: “Fast Algorithms for Low-Level Vision”; IEEE Transactions on Pattern Analysis and Machine Intelligence; PAMI-12, no. 1; S. 78-87; 1990.

Module

Foundation