hints

General tips

In general you should always experiment with different color settings. Some filters just seem to do nothing when the default colors (black and white) are selected. To accomplish this use the number keys (1-8) with or without shift to directly set the primary and secondary color. For further adjustment use the u,i,o and j,k,l with shift and/or ctrl.

When using the sobel filter the image might improve when adjusting the filter parameter using the up and down arrow keys (holding ctrl allows for smaller steps).

Try the effect with grayscale mode on or off (use the g key to toggle). Some filters (e.g. sobel) won't look different because they only use the gray component, but some filters especially the and and xor filters often look completely different.

The and and xor filter

The xor and and filters are easy to describe. They take every pixel and perform a logical xor or and with the primary color. These operation work on a bitwise base. With and a bit is only 1 if both input bits are 1 otherwise its 0. With xor the bit is 1 if exactly one of the input bits is 1.

The simplest colors you can pick are black and white. Using black with the and filter results in blackness while using white has no effect at all. With the xor filter black has no effect while white inverts the image

Interesting effects can be achieved using color values as 808080 or 0f0f0f with both filters. You also should try different masks for each color component. For example using 00ff00 with and gives you only the green part of the image.

Everything said in the first section is even more true for the and and xor filters: always keep experimenting - this way you'll get the best effects.