"Defish", barrel and pincushion distortion correction filter

[wonkey_monkey]

Updated 2010/02/21 - version 1.1

Download: defish

It's taken me several years since my first post on this subject, but I've finally written a usable fisheye distortion correction plugin:



It uses spline16 interpolation.

defish (v1.1) for Avisynth 2.5
(c) David Horman, 2010

This filter can be used to correct (or induce) barrel and pincushion
distortion.

USAGE
-----

The filter takes the following parameters (in addition to the input clip):

[unnamed]:
	Input clip. Must be RGB32 and have even width/height.

fov:
	useful range: -180.0 - 180.0
	default: 0
	The horizontal field of view, in degrees. Positive values will
	correct barrel distortion (induce pincushioning). Negative values
	should correct pincushion distortion (induce barreling), but note
	that this may currently be implemented incorrectly.

scale:
        range: 0.0 - infinity
	default: 1.0
	An adjustment parameter which scales the image after correction.

aspect:
	range: 0.0 - infinity
	default: 1.0
	The pixel aspect ratio of the input clip.

direction:
	values: "x", "y"
	This parameter restricts the correction to either horizontal or
	vertical only.

scaling:
	values: "fitx", "fity", "fitxy"
	This parameter automatically scales the image to fill the image
	horizontally, vertically, or both. The "scale" parameter above is
	still effective.

	The default behaviour when using fov is to scale the image such
	that the central area stays at the original scale.

	This parameter is not effective when using the polynomial values
	below.
a,b,c:
        sensible range: 0.0 - 1.0
        Parameters for correcting distortion polynomially. These are only
        effective when fov=0 (which is the default value).

        a+b+c must be less than or equal to 1.0 when pin=true.

pin:
	boolean
	Set this to true to correct pincushion distortion, and false to
	correct	barrel distortion - this may seem the wrong way around but
	it was chosen to match the behaviour of the similar parameter of
	V.C. Mohan's DeBarrel filter.

David