libvips/libsrc/conversion/im_subsample.c

248 lines
5.4 KiB
C

/* @(#) Shrink any image by some integer xy factor. Sub-samples! Partial, and
* @(#) quick as a result.
* @(#)
* @(#) int
* @(#) im_subsample( in, out, xshrink, yshrink )
* @(#) IMAGE *in, *out;
* @(#) int xshrink, yshrink;
* @(#)
* @(#) Returns either 0 (success) or -1 (fail)
* @(#)
*
* 3/7/95 JC
* - adapted from im_shrink()
* 3/8/02 JC
* - fall back to im_copy() for x/y factors == 1
*/
/*
This file is part of VIPS.
VIPS is free software; you can redistribute it and/or modify
it under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
/*
These files are distributed with VIPS - http://www.vips.ecs.soton.ac.uk
*/
#ifdef HAVE_CONFIG_H
#include <config.h>
#endif /*HAVE_CONFIG_H*/
#include <vips/intl.h>
#include <stdio.h>
#include <stdlib.h>
#include <vips/vips.h>
#ifdef WITH_DMALLOC
#include <dmalloc.h>
#endif /*WITH_DMALLOC*/
/* Maximum width of input we ask for.
*/
#define IM_MAX_WIDTH (1000)
/* Our main parameter struct.
*/
typedef struct {
int xshrink; /* Subsample factors */
int yshrink;
} SubsampleInfo;
/* Subsample a REGION. We fetch in IM_MAX_WIDTH pixel-wide strips, left-to-right
* across the input.
*/
static int
line_shrink_gen( REGION *or, void *seq, void *a, void *b )
{
REGION *ir = (REGION *) seq;
IMAGE *in = (IMAGE *) a;
SubsampleInfo *st = (SubsampleInfo *) b;
Rect *r = &or->valid;
int le = r->left;
int ri = IM_RECT_RIGHT( r );
int to = r->top;
int bo = IM_RECT_BOTTOM(r);
int ps = IM_IMAGE_SIZEOF_PEL( in );
int owidth = IM_MAX_WIDTH / st->xshrink;
Rect s;
int x, y;
int z, k;
/* Loop down the region.
*/
for( y = to; y < bo; y++ ) {
char *q = IM_REGION_ADDR( or, le, y );
char *p;
/* Loop across the region, in owidth sized pieces.
*/
for( x = le; x < ri; x += owidth ) {
/* How many pixels do we make this time?
*/
int ow = IM_MIN( owidth, ri - x );
/* Ask for this many from input ... can save a
* little here!
*/
int iw = ow * st->xshrink - (st->xshrink - 1);
/* Ask for input.
*/
s.left = x * st->xshrink;
s.top = y * st->yshrink;
s.width = iw;
s.height = 1;
if( im_prepare( ir, &s ) )
return( -1 );
/* Append new pels to output.
*/
p = IM_REGION_ADDR( ir, s.left, s.top );
for( z = 0; z < ow; z++ ) {
for( k = 0; k < ps; k++ )
q[k] = p[k];
q += ps;
p += ps * st->xshrink;
}
}
}
return( 0 );
}
/* Fetch one pixel at a time ... good for very large shrinks, or for SMALLTILE
* pipes.
*/
static int
point_shrink_gen( REGION *or, void *seq, void *a, void *b )
{
REGION *ir = (REGION *) seq;
IMAGE *in = (IMAGE *) a;
SubsampleInfo *st = (SubsampleInfo *) b;
Rect *r = &or->valid;
int le = r->left;
int ri = IM_RECT_RIGHT( r );
int to = r->top;
int bo = IM_RECT_BOTTOM(r);
int ps = IM_IMAGE_SIZEOF_PEL( in );
Rect s;
int x, y;
int k;
/* Loop down the region.
*/
for( y = to; y < bo; y++ ) {
char *q = IM_REGION_ADDR( or, le, y );
char *p;
/* Loop across the region, in owidth sized pieces.
*/
for( x = le; x < ri; x++ ) {
/* Ask for input.
*/
s.left = x * st->xshrink;
s.top = y * st->yshrink;
s.width = 1;
s.height = 1;
if( im_prepare( ir, &s ) )
return( -1 );
/* Append new pels to output.
*/
p = IM_REGION_ADDR( ir, s.left, s.top );
for( k = 0; k < ps; k++ )
q[k] = p[k];
q += ps;
}
}
return( 0 );
}
int
im_subsample( IMAGE *in, IMAGE *out, int xshrink, int yshrink )
{
SubsampleInfo *st;
/* Check parameters.
*/
if( xshrink < 1 || yshrink < 1 ) {
im_errormsg( "im_subsample: factors should both be >= 1" );
return( -1 );
}
if( xshrink == 1 && yshrink == 1 )
return( im_copy( in, out ) );
if( im_piocheck( in, out ) )
return( -1 );
/* Prepare output. Note: we round the output width down!
*/
if( im_cp_desc( out, in ) )
return( -1 );
out->Xsize = in->Xsize / xshrink;
out->Ysize = in->Ysize / yshrink;
out->Xres = in->Xres / xshrink;
out->Yres = in->Yres / yshrink;
if( out->Xsize <= 0 || out->Ysize <= 0 ) {
im_errormsg( "im_subsample: image has shrunk to nothing" );
return( -1 );
}
/* Build and attach state struct.
*/
if( !(st = IM_NEW( out, SubsampleInfo )) )
return( -1 );
st->xshrink = xshrink;
st->yshrink = yshrink;
/* Set demand hints. We want THINSTRIP, as we will be demanding a
* large area of input for each output line.
*/
if( im_demand_hint( out, IM_THINSTRIP, in, NULL ) )
return( -1 );
/* Generate! If this is a very large shrink, then it's
* probably faster to do it a pixel at a time. If this is SMALLTILE,
* then it will hate long lines and we should always do 1 pixel at a
* time.
*/
if( in->dhint == IM_SMALLTILE || xshrink > 10 ) {
if( im_generate( out,
im_start_one, point_shrink_gen, im_stop_one, in, st ) )
return( -1 );
}
else {
if( im_generate( out,
im_start_one, line_shrink_gen, im_stop_one, in, st ) )
return( -1 );
}
return( 0 );
}