im_similarity_area(3)

NAME

im_similarity_area, im_similarity - apply a similarity

transform to an
image

SYNOPSIS

#include <vips/vips.h>
int im_similarity_area(in, out, s, a, dx, dy, x, y, w, h)
IMAGE *in, *out;
double s, a, dx, dy;
int x, y;
int w, h;
int im_similarity(in, out, s, a, dx, dy)
IMAGE *in, *out;
double s, a, dx, dy;

DESCRIPTION

im_similarity_area() applies a similarity 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 num

ber of bands,
be any size, and have any non-complex type.

The transformation is described by s, a, dx, dy. The

point (x,y) in
the input is mapped onto point (X,Y) in the output by

X = s * x - a * y + dx Y = a * x + s * y + dy

s and a do not correspond to scale and angle of the trans

formation; the
actual scale and angle are given by the equations:

scale = sqrt(s*s + a*a) angle = arctan(s/a).

The area of the output image given by x, y, w, h is gener

ated. (0,0) is
the position of the transformed top-left-hand corner

of the input
image. Function im_similarity_area resamples the

transformed image
using bilinear interpolation.

im_similarity works exactly as im_similarity_area, but

calculates x, y,
w, h for you such that the rectangle described just en

closes all of the
transformed input pixels.

RETURN VALUE

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

BUGS

As with most resamplers, im_similarity performs poorly at

the edges of
images.

SEE ALSO

similarity(1), similarity_area(1)

AUTHORS

N. Dessipris - 13/01/1992
J.Ph. Laurent - 12/12/92
J. Cupitt - 22/02/93

13 January 1992 IM_SIMI

LARITY_AREA(3)