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libvips/libvips/resample/shrink.c

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/* shrink with a box filter
*
* Copyright: 1990, N. Dessipris.
*
* Authors: Nicos Dessipris and Kirk Martinez
* Written on: 29/04/1991
* Modified on: 2/11/92, 22/2/93 Kirk Martinez - Xres Yres & cleanup
incredibly inefficient for box filters as LUTs are used instead of +
Needs converting to a smoother filter: eg Gaussian! KM
* 15/7/93 JC
* - rewritten for partial v2
* - ANSIfied
* - now shrinks any non-complex type
* - no longer cloned from im_convsub()
* - could be much better! see km comments above
* 3/8/93 JC
* - rounding bug fixed
* 11/1/94 JC
* - problems with .000001 and round up/down ignored! Try shrink 3738
* pixel image by 9.345000000001
* 7/10/94 JC
* - IM_NEW and IM_ARRAY added
* - more typedef
* 3/7/95 JC
* - IM_CODING_LABQ handling added here
* 20/12/08
* - fall back to im_copy() for 1/1 shrink
* 2/2/11
* - gtk-doc
* 10/2/12
* - shrink in chunks to reduce peak memuse for large shrinks
* - simpler
* 12/6/12
* - redone as a class
* - warn about non-int shrinks
* - some tuning .. tried an int coordinate path, not worthwhile
* 16/11/12
* - don't change xres/yres, see comment below
* 8/4/13
* - oops demand_hint was incorrect, thanks Jan
* 6/6/13
* - don't chunk horizontally, fixes seq problems with large shrink
* factors
*/
/*
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., 51 Franklin Street, Fifth Floor, Boston, MA
02110-1301 USA
*/
/*
These files are distributed with VIPS - http://www.vips.ecs.soton.ac.uk
*/
/*
#define DEBUG
*/
#ifdef HAVE_CONFIG_H
#include <config.h>
#endif /*HAVE_CONFIG_H*/
#include <vips/intl.h>
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <vips/vips.h>
#include <vips/debug.h>
#include "presample.h"
typedef struct _VipsShrink {
VipsResample parent_instance;
double xshrink; /* Shrink factors */
double yshrink;
int mw; /* Size of area we average */
int mh;
int np; /* Number of pels we average */
} VipsShrink;
typedef VipsResampleClass VipsShrinkClass;
G_DEFINE_TYPE( VipsShrink, vips_shrink, VIPS_TYPE_RESAMPLE );
/* Our per-sequence parameter struct. Somewhere to sum band elements.
*/
typedef struct {
VipsRegion *ir;
VipsPel *sum;
} VipsShrinkSequence;
/* Free a sequence value.
*/
static int
vips_shrink_stop( void *vseq, void *a, void *b )
{
VipsShrinkSequence *seq = (VipsShrinkSequence *) vseq;
VIPS_FREEF( g_object_unref, seq->ir );
return( 0 );
}
/* Make a sequence value.
*/
static void *
vips_shrink_start( VipsImage *out, void *a, void *b )
{
VipsImage *in = (VipsImage *) a;
VipsShrink *shrink = (VipsShrink *) b;
VipsShrinkSequence *seq;
if( !(seq = IM_NEW( out, VipsShrinkSequence )) )
return( NULL );
/* Init!
*/
seq->ir = vips_region_new( in );
if( !(seq->sum = (VipsPel *) VIPS_ARRAY( out, in->Bands, double )) ) {
vips_shrink_stop( seq, in, shrink );
return( NULL );
}
return( (void *) seq );
}
/* Integer shrink.
*/
#define ISHRINK( TYPE ) { \
int *sum = (int *) seq->sum; \
TYPE *p = (TYPE *) in; \
TYPE *q = (TYPE *) out; \
\
for( b = 0; b < bands; b++ ) \
sum[b] = 0; \
\
for( y1 = 0; y1 < shrink->mh; y1++ ) { \
for( i = 0, x1 = 0; x1 < shrink->mw; x1++ ) \
for( b = 0; b < bands; b++, i++ ) \
sum[b] += p[i]; \
\
p += ls; \
} \
\
for( b = 0; b < bands; b++ ) \
q[b] = (sum[b] + shrink->np / 2) / shrink->np; \
}
/* Float shrink.
*/
#define FSHRINK( TYPE ) { \
double *sum = (double *) seq->sum; \
TYPE *p = (TYPE *) in; \
TYPE *q = (TYPE *) out; \
\
for( b = 0; b < bands; b++ ) \
sum[b] = 0.0; \
\
for( y1 = 0; y1 < shrink->mh; y1++ ) { \
for( i = 0, x1 = 0; x1 < shrink->mw; x1++ ) \
for( b = 0; b < bands; b++, i++ ) \
sum[b] += p[i]; \
\
p += ls; \
} \
\
for( b = 0; b < bands; b++ ) \
q[b] = sum[b] / shrink->np; \
}
/* Generate an area of @or. @ir is large enough.
*/
static void
vips_shrink_gen2( VipsShrink *shrink, VipsShrinkSequence *seq,
VipsRegion *or, VipsRegion *ir,
int left, int top, int width, int height )
{
VipsResample *resample = VIPS_RESAMPLE( shrink );
const int bands = resample->in->Bands;
const int sizeof_pixel = VIPS_IMAGE_SIZEOF_PEL( resample->in );
const int ls = VIPS_REGION_LSKIP( ir ) /
VIPS_IMAGE_SIZEOF_ELEMENT( resample->in );
int x, y, i;
int x1, y1, b;
for( y = 0; y < height; y++ ) {
VipsPel *out = VIPS_REGION_ADDR( or, left, top + y );
for( x = 0; x < width; x++ ) {
int ix = (left + x) * shrink->xshrink;
int iy = (top + y) * shrink->yshrink;
VipsPel *in = VIPS_REGION_ADDR( ir, ix, iy );
switch( resample->in->BandFmt ) {
case VIPS_FORMAT_UCHAR:
ISHRINK( unsigned char ); break;
case VIPS_FORMAT_CHAR:
ISHRINK( char ); break;
case VIPS_FORMAT_USHORT:
ISHRINK( unsigned short ); break;
case VIPS_FORMAT_SHORT:
ISHRINK( short ); break;
case VIPS_FORMAT_UINT:
ISHRINK( unsigned int ); break;
case VIPS_FORMAT_INT:
ISHRINK( int ); break;
case VIPS_FORMAT_FLOAT:
FSHRINK( float ); break;
case VIPS_FORMAT_DOUBLE:
FSHRINK( double ); break;
default:
g_assert( 0 );
}
out += sizeof_pixel;
}
}
}
static int
vips_shrink_gen( VipsRegion *or, void *vseq, void *a, void *b, gboolean *stop )
{
VipsShrinkSequence *seq = (VipsShrinkSequence *) vseq;
VipsShrink *shrink = (VipsShrink *) b;
VipsRegion *ir = seq->ir;
VipsRect *r = &or->valid;
/* How do we chunk up the image? We don't want to prepare the whole of
* the input region corresponding to *r since it could be huge.
*
* Each pixel of *r will depend on roughly mw x mh
* pixels, so we walk *r in chunks which map to the tile size.
*
* Make sure we can't ask for a zero step.
*
* We don't chunk horizontally. We want "vips shrink x.jpg b.jpg 100
* 100" to run sequentially. If we chunk horizontally, we will fetch
* 100x100 lines from the top of the image, then 100x100 100 lines
* down, etc. for each thread, then when they've finished, fetch
* 100x100, 100 pixels across from the top of the image. This will
* break sequentiality.
*/
int ystep = shrink->mh > VIPS__TILE_HEIGHT ?
1 : VIPS__TILE_HEIGHT / shrink->mh;
int y;
#ifdef DEBUG
printf( "vips_shrink_gen: generating %d x %d at %d x %d\n",
r->width, r->height, r->left, r->top );
#endif /*DEBUG*/
for( y = 0; y < r->height; y += ystep ) {
/* Clip the this rect against the demand size.
*/
int height = VIPS_MIN( ystep, r->height - y );
VipsRect s;
s.left = r->left * shrink->xshrink;
s.top = (r->top + y) * shrink->yshrink;
s.width = ceil( r->width * shrink->xshrink );
s.height = ceil( height * shrink->yshrink );
#ifdef DEBUG
printf( "shrink_gen: requesting %d x %d at %d x %d\n",
s.width, s.height, s.left, s.top );
#endif /*DEBUG*/
if( vips_region_prepare( ir, &s ) )
return( -1 );
vips_shrink_gen2( shrink, seq,
or, ir,
r->left, r->top + y, r->width, height );
}
return( 0 );
}
static int
vips_shrink_build( VipsObject *object )
{
VipsObjectClass *class = VIPS_OBJECT_GET_CLASS( object );
VipsResample *resample = VIPS_RESAMPLE( object );
VipsShrink *shrink = (VipsShrink *) object;
if( VIPS_OBJECT_CLASS( vips_shrink_parent_class )->build( object ) )
return( -1 );
shrink->mw = ceil( shrink->xshrink );
shrink->mh = ceil( shrink->yshrink );
shrink->np = shrink->mw * shrink->mh;
if( vips_check_noncomplex( class->nickname, resample->in ) )
return( -1 );
if( shrink->xshrink < 1.0 ||
shrink->yshrink < 1.0 ) {
vips_error( class->nickname,
"%s", _( "shrink factors should be >= 1" ) );
return( -1 );
}
if( (int) shrink->xshrink != shrink->xshrink ||
(int) shrink->yshrink != shrink->yshrink )
vips_warn( class->nickname,
"%s", _( "not integer shrink factors, "
"expect poor results" ) );
if( shrink->xshrink == 1.0 &&
shrink->yshrink == 1.0 )
return( vips_image_write( resample->in, resample->out ) );
if( vips_image_copy_fields( resample->out, resample->in ) )
return( -1 );
/* THINSTRIP will work, anything else will break seq mode. If you
* combine shrink with conv you'll need to use a line cache to maintain
* sequentiality.
*/
vips_demand_hint( resample->out,
VIPS_DEMAND_STYLE_THINSTRIP, resample->in, NULL );
/* Size output. Note: we round the output width down!
*
* Don't change xres/yres, leave that to the application layer. For
* example, vipsthumbnail knows the true shrink factor (including the
* fractional part), we just see the integer part here.
*/
resample->out->Xsize = resample->in->Xsize / shrink->xshrink;
resample->out->Ysize = resample->in->Ysize / shrink->yshrink;
if( resample->out->Xsize <= 0 ||
resample->out->Ysize <= 0 ) {
vips_error( class->nickname,
"%s", _( "image has shrunk to nothing" ) );
return( -1 );
}
#ifdef DEBUG
printf( "vips_shrink_build: shrinking %d x %d image to %d x %d\n",
resample->in->Xsize, resample->in->Ysize,
resample->out->Xsize, resample->out->Ysize );
printf( "vips_shrink_build: %d x %d block average\n",
shrink->mw, shrink->mh );
#endif /*DEBUG*/
if( vips_image_generate( resample->out,
vips_shrink_start, vips_shrink_gen, vips_shrink_stop,
resample->in, shrink ) )
return( -1 );
return( 0 );
}
static void
vips_shrink_class_init( VipsShrinkClass *class )
{
GObjectClass *gobject_class = G_OBJECT_CLASS( class );
VipsObjectClass *vobject_class = VIPS_OBJECT_CLASS( class );
VipsOperationClass *operation_class = VIPS_OPERATION_CLASS( class );
VIPS_DEBUG_MSG( "vips_shrink_class_init\n" );
gobject_class->set_property = vips_object_set_property;
gobject_class->get_property = vips_object_get_property;
vobject_class->nickname = "shrink";
vobject_class->description = _( "shrink an image" );
vobject_class->build = vips_shrink_build;
operation_class->flags = VIPS_OPERATION_SEQUENTIAL;
VIPS_ARG_DOUBLE( class, "xshrink", 8,
_( "Xshrink" ),
_( "Horizontal shrink factor" ),
VIPS_ARGUMENT_REQUIRED_INPUT,
G_STRUCT_OFFSET( VipsShrink, xshrink ),
1.0, 1000000, 1 );
VIPS_ARG_DOUBLE( class, "yshrink", 9,
_( "Yshrink" ),
_( "Vertical shrink factor" ),
VIPS_ARGUMENT_REQUIRED_INPUT,
G_STRUCT_OFFSET( VipsShrink, yshrink ),
1.0, 1000000, 1 );
}
static void
vips_shrink_init( VipsShrink *shrink )
{
}
/**
* vips_shrink:
* @in: input image
* @out: output image
* @xshrink: horizontal shrink
* @yshrink: vertical shrink
*
* Shrink @in by a pair of factors with a simple box filter.
*
* You will get aliasing for non-integer shrinks. In this case, shrink with
* this function to the nearest integer size above the target shrink, then
* downsample to the exact size with vips_affine() and your choice of
* interpolator.
*
* See also: vips_affine().
*
* Returns: 0 on success, -1 on error
*/
int
vips_shrink( VipsImage *in, VipsImage **out,
double xshrink, double yshrink, ... )
{
va_list ap;
int result;
va_start( ap, yshrink );
result = vips_call_split( "shrink", ap, in, out, xshrink, yshrink );
va_end( ap );
return( result );
}
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