.. _net.sf.cimg.CImgLaplacian:

Laplacian node
==============

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*This documentation is for version 4.0 of Laplacian (net.sf.cimg.CImgLaplacian).*

Description
-----------

Blur input stream, and subtract the result from the input image. This is not a mathematically correct Laplacian (which would be the sum of second derivatives over X and Y).

Uses the ‘vanvliet’ and ‘deriche’ functions from the CImg library.

CImg is a free, open-source library distributed under the CeCILL-C (close to the GNU LGPL) or CeCILL (compatible with the GNU GPL) licenses. It can be used in commercial applications (see http://cimg.eu).

Inputs
------

+--------+-------------+----------+
| Input  | Description | Optional |
+========+=============+==========+
| Source |             | No       |
+--------+-------------+----------+
| Mask   |             | Yes      |
+--------+-------------+----------+

Controls
--------

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+------------------------------+---------+-----------+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Parameter / script name      | Type    | Default   | Function                                                                                                                                                                                                                             |
+==============================+=========+===========+======================================================================================================================================================================================================================================+
| Size / ``size``              | Double  | x: 3 y: 3 | Size (diameter) of the filter kernel, in pixel units (>=0). The standard deviation of the corresponding Gaussian is size/2.4. No blur is applied if size < 0.24 (Gaussian and quasi-Gaussian) or <= 1 (box, triangle and quadratic). |
+------------------------------+---------+-----------+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Uniform / ``uniform``        | Boolean | Off       | Apply the same amount of blur on X and Y.                                                                                                                                                                                            |
+------------------------------+---------+-----------+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Filter / ``filter``          | Choice  | Gaussian  | | Bluring filter. The quasi-Gaussian filter should be appropriate in most cases. The Gaussian filter is more isotropic (its impulse response has rotational symmetry), but slower.                                                   |
|                              |         |           | | **Quasi-Gaussian (quasigaussian)**: Quasi-Gaussian filter (0-order recursive Deriche filter, faster) - IIR (infinite support / impulsional response).                                                                              |
|                              |         |           | | **Gaussian (gaussian)**: Gaussian filter (Van Vliet recursive Gaussian filter, more isotropic, slower) - IIR (infinite support / impulsional response).                                                                            |
|                              |         |           | | **Box (box)**: Box filter - FIR (finite support / impulsional response).                                                                                                                                                           |
|                              |         |           | | **Triangle (triangle)**: Triangle/tent filter - FIR (finite support / impulsional response).                                                                                                                                       |
|                              |         |           | | **Quadratic (quadratic)**: Quadratic filter - FIR (finite support / impulsional response).                                                                                                                                         |
+------------------------------+---------+-----------+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| (Un)premult / ``premult``    | Boolean | Off       | Divide the image by the alpha channel before processing, and re-multiply it afterwards. Use if the input images are premultiplied.                                                                                                   |
+------------------------------+---------+-----------+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Invert Mask / ``maskInvert`` | Boolean | Off       | When checked, the effect is fully applied where the mask is 0.                                                                                                                                                                       |
+------------------------------+---------+-----------+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Mix / ``mix``                | Double  | 1         | Mix factor between the original and the transformed image.                                                                                                                                                                           |
+------------------------------+---------+-----------+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+

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