im_rightshift_size - Decrease size by a power-of-two factor
int im_rightshift_size( IMAGE *in, IMAGE *out, int xshift, int yshift, int band_fmt );
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. xshift and yshift are positive and give the base-two
logarithms of the scale factors.
If the input image is a signed type, then band_fmt must be one of
IM_BANDFMT_CHAR, IM_BANDFMT_SHORT or IM_BANDFMT_INT. If it is an
unsigned type, then band_fmt must be one of IM_BANDFMT_UCHAR,
IM_BANDFMT_USHORT or IM_BANDFMT_UINT.
The functions returns 0 on success and -1 on error.
Copyright 2006, Tom Vajzovic.
12 August 2006