User Guide
GNU Image Manipulation Program
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Reflective Reflective: Waves bounce on sides and interfere with the arriving ones.
Amplitude Amplitude: Varies the height of waves.
Phase Phase: This command shifts the top of waves.
Wavelength Wavelength: Varies the distance between the top of waves.
15.10.15 Whirl and Pinch
15.10.15.1 Overview
Figure 15.166: Example for the Whirl and Pinch filter
(a) Original image (b) Filter applied
You can find this filter through Filters → Distorts → Whirl and Pinch
"Whirl and Pinch" distorts your image in a concentric way.
"Whirl" distorts the image much like the little whirlpool that appears when you empty your bath.
"Pinch" can be compared to applying your image to a soft rubber surface and squeezing the edges or corners. If the Pinch amount
slider is set to a negative value, it will look as if someone tried to push a round object up toward you from behind the rubber skin.
If the Pinch amount is set to a positive value, it looks like someone is dragging or sucking on the surface from behind, and away
from you.
Tip
The ‘pinch’ effect can sometimes be used to compensate for image distortion produced by telephoto or fisheye lenses
(‘barrel distortion’).