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im_affine

NAME

im_affine - apply an affine transform to an image

SYNOPSIS

#include <vips/vips.h>

int im_affine(in, out, a, b, c, d, dx, dy, x, y, w, h)
IMAGE *in, *out;
double a, b, c, d, dx, dy;
int x, y;
int w, h;

DESCRIPTION

im_affine() 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. Function im_affine resamples the transformed image using bilinear interpolation.

You can use im_affine(3) to resize an image with something like:

  scale xfac yfac im
    = im_affine im xfac 0 0 yfac 0 0 0 0 
        (im.width * xfac) (im.height * yfac);

RETURN VALUE

The functions return 0 on success and -1 on error.

BUGS

As with most resamplers, im_affine(3) performs poorly at the edges of images.

SEE ALSO

im_similarity(3)