The filter is a matrix that is applied to a set of samples from the input, with each sample multiplied by an amount, and all the samples added together. Then the result is divided by an amount and that color is returned.
Public Member Functions  
void  input (Brush value) 
Set the input brush.  
void  divisor (float value) 
Set the divisor.  
float  findDivisor () 
Get the set divisor or compute it.  
void  resize (int value) 
Resize the square matrix.  
void  center (int x, int y) 
Set the center of the filter matrix.  
void  set (int x, int y, float v) 
Set a cell on the filter.  
void  setLineEdge () 
Set to a line edge filter.  
void  setHighPass (float scale) 
Set to a high pass filter.  
Color  eval (float x, float y) 
Evaluate the filter. 

Set the center of the filter matrix. For example, (1, 1) on a 3x3 filter makes the (1, 1) coordinate the input point. 

Set the divisor. When the divisor is not set, it is set according to the sum of the cells in the matrix. You can restore this property by setting the divisor to float.nan. 

Resize the square matrix. This clears all cells to zero. 