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The convolutions menu

  The image convolution menu

This menu provides filters which work by looking at a neighbourhood around every pixel in the image. The neighbourhood of a pixel is a square array, n x n. The size of the neighbourhood, n, is often specified in terms of a "half width" such that n = 2 x halfwidth + 1.

Three groups of filters are available:

In all of the menu options we talk about the half-width (h) of the kernel or pixel neighbourhood. The kernel needs to have an odd width and height so that the pixel being processed can be at its centre. So width and height of the n x n neighbourhood are given by the formula n = 2 x h + 1. Note that pixels at the edge of the image, within the half-width of the kernel, would not be properly processed so they are set to black. So the image gradually shrinks as you apply convolutions. Note also that there is only one kernel set in GRIP at any time, so setting it on one image frame will make it available for all open images. The same applies to the deconvolution settings (in Java terms, they are all static).

When processing coloured images each of the channels (colour bands) is processed completely independently of the others.


 Non-linear convolutions


 Linear convolutions



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