5.14. Whirl and Pinch

5.14. Whirl and Pinch
	5. Distort Filters

5.14.1. Overview

Figure 17.87. Example for the Whirl and Pinch filter

Original image

Filter applied

“Whirl and Pinch” distorts your image in a concentric way.

“Whirl” (applying a non-zero Whirl angle) distorts the image much like the little whirlpool that appears when you empty your bath.

“Pinch”, with a nil rotation, 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 fish-eye lenses (“barrel distortion”).

Figure 17.88. Illustration

Original

Whirled

Pinched

5.14.2. Activating the filter

You can find this filter through Filters → Distorts → Whirl and Pinch…

5.14.3. Parameter Settings

Figure 17.89. “Whirl and Pinch” filter options

Presets, Preview, Split view

	Note
	These options are described in Section 2, “Common Features”.

Whirl angle

Clockwise or counter clockwise (-360 to +360). Controls how many degrees the affected part of the image is rotated.

Pinch amount

Whirlpool depth(-1 to +1). Determines how strongly the affected part of the image is pinched.

Radius

Whirlpool width (0.0-2.0). Determines how much of the image is affected by the distortion. If you set Radius to 2, the entire image will be affected. If you set Radius to 1, half the image will be affected. If Radius is set to 0, nothing will be affected (think of it as the radius in a circle with 0 in the center and 1 halfway out).

Clipping

The result of this filter can be larger than the original image. With the default Adjust option, the layer will be automatically resized as necessary when the filter is applied. With the Clip option the result will be clipped to the layer boundary.