.TH IM_AFFINEI 3 "8 February 2009"
.SH NAME
im_affinei \- apply an affine transform to an image
.SH SYNOPSIS
.B #include <vips/vips.h>

int im_affinei(in, out, interpolate, a, b, c, d, dx, dy, x, y, w, h)
.br
.B IMAGE *in, *out;
.br
.B VipsInterpolate *interpolate;
.br
.B double a, b, c, d, dx, dy;
.br
.B int x, y;
.br
.B int w, h;

int im_affinei_all(in, out, interpolate, a, b, c, d, dx, dy)
.br
.B IMAGE *in, *out;
.br
.B VipsInterpolate *interpolate;
.br
.B double a, b, c, d, dx, dy;

.SH DESCRIPTION
.B im_affinei(3)
applies an affine transformation on the image held by the IMAGE descriptor
in and puts the result at the location pointed by the IMAGE descriptor out. in
many have any number of bands, be any size, and have any non-complex type.

The transformation is described by a, b, c, d, dx, dy.  The point (x,y) in 
the input is mapped onto point (X,Y) in the output by

  X = a * x + b * y + dx
  Y = c * x + d * y + dy

The area of the output image given by w, h, x, y is generated. (0,0) is 
the position of the transformed top-left-hand corner of the input image.

Points are generated using the supplied interpolator. See 
.B VipsInterpolate(3)
for a list of the interpolators that come with vips. 

.B im_affinei_all(3) 
is a convenience function that transforms the whole of the input image. It
calls 
.B im_affine(3) 
for you, with x y w h set to exactly enclose the transformed image.

.SH RETURN VALUE
The functions return 0 on success and -1 on error.
.SH BUGS
As with most resamplers, im_affine(3) performs poorly at the edges of
images.
.SH SEE ALSO
im_similarity(3)