These filters, with the exception of Reduce Noise and Dither, are implemented using 3 x 3 spatial convolutions, where the value of each pixel in the selection is replaced with the weighted average of its 3 x 3 neighborhood. They are not limited to rectangular selections. The entire image is filtered if no selection is active. They do not work correctly with 8-bit true color images. They can be aborted by typing command-period. The 3 x 3 tables shown below are the coefficients (weighting factors) for the filters.

Shadow produces a shadow effect, with the light appearing to come from a direction specified in a dialog box. Three of the kernels used are shown below.

West

North West

North

1	0	–1		2	1	0		1	2	1
2	1	–2		1	1	–1		0	1	0
1	0	–1		0	–1	–2		–1	–2	–1