.TH IM_RIGHTSHIFT_SIZE 3 "12 August 2006"
.SH NAME
 im_rightshift_size \- Decrease size by a power-of-two factor
.SH SYNOPSIS
.nf
.B #include <vips/vips.h>
.sp
.BI "int im_rightshift_size( IMAGE " "*in" ", IMAGE " "*out" ", int " "xshift" ", int " "yshift" ", int " "band_fmt" " );
.fi
.SH DESCRIPTION
.B im_rightshift_size(3)
decreases the size of an integer type image by a power-of-two factor, very quickly, by summing the values of
adjacent pixels.  The sum is shifted to produce output of the specified band format.  
.IR xshift " and "yshift
are positive and give the base-two logarithms of the scale factors.
.PP
If the input image is a signed type, then 
.I band_fmt
must be one of IM_BANDFMT_CHAR, IM_BANDFMT_SHORT or IM_BANDFMT_INT.  If it is an unsigned type, then
.I band_fmt
must be one of IM_BANDFMT_UCHAR, IM_BANDFMT_USHORT or IM_BANDFMT_UINT.
.SH RETURN VALUE
The functions returns 0 on success and -1 on error.
.SH SEE ALSO
im_affine(3)
.SH COPYRIGHT
.br
Copyright 2006, Tom Vajzovic.
.SH AUTHOR
Tom Vajzovic