Effects > Artistic > User Defined 
User Defined 
The User Defined filter allows you to create user defined filters using a convolution matrix. Convolution is central to modern image processing. The basic idea is that a window of some finite size and shape is scanned across the image. The output pixel value is the weighted sum of the input pixels within the window where the weights are the values of the filter assigned to every pixel of the window itself. The window with its weights is called the convolution kernel. 

1.  Choose Effects > Artistic > User Defined 
2.  Use the following options: 

Convolution Matrix


Change the values of the convolution matrix or select one of the examples.



Channels


Select one or more color channels to apply the effect to or choose gray.



