Example for the “Predator” filter
This filter adds a “Predator” effect to the image. The
predator effect makes the image/selection look something like the view
the predator has in movies (kind of a thermogram and that type of
thing). This will reduce the image to edges in a few basic colors on a
If there is an active selection, the filter effect will be applied to
the selected region, otherwise to the alpha channel (the filter will
add an alpha channel, if necessary). The filter works best on colorful
Activate the filter
This filter is found in the image window menu under
→ → .
The “predator” filter will detect edges using the
Sobel edge detector. The
specified “Edge amount” will be passed to the Sobel
filter. A high value will result in detecting more edges.
“Edge amount” examples
If checked, the filter will simplify the image into solid-colored
squares using the Pixelise
filter before the real predator effect will be applied. You can
select the size of these squares with the option Pixel
amount, which will heavily affect the result (see
“Pixel amount” is the size of the color blocks the
image will be simplified to if Pixelize is
checked. Actually you are decreasing the resolution with this
option. In the examples below, you can see directly how increasing
the pixel block size leads to something like
If checked, the filter will be applied to the active selection.
Else, it will be applied to the active layer.
When this option is checked, a copy of the active layer will be
created above the active layer and the filter will be applied to
this copy, leaving the original layer untouched. If not checked,
the filter will be applied to the active layer.
Since this filter delegates the essential parts to two or three other
filters the algorithm is very simple:
Making the “predator” effect
The original image.
Optionally, the filter
pixelizes the image: it
renders the image by using color blocks instead of pixels, thus
reducing the image resolution.
The colors will be reduced to pure red, green, blue (and possibly
gray colors), using the minimal
RGB channel for every pixel.
Applying the Sobel edge
detecting filter, the image will be reduced further on to
edges, usually on a black background, with very few colors.