340 lines
8.3 KiB
C
340 lines
8.3 KiB
C
/* subsample
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*
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* 3/7/95 JC
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* - adapted from im_shrink()
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* 3/8/02 JC
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* - fall back to im_copy() for x/y factors == 1
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* 21/4/08
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* - don't fall back to pixel-wise shrinks for smalltile, it kills
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* performance, just bring VIPS_MAX_WIDTH down instead
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* 1/2/10
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* - gtkdoc
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* 1/6/13
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* - redo as a class
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* 2/11/13
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* - add @point to force point sample mode
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* 22/1/16
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* - remove SEQUENTIAL hint, it confuses vips_sequential()
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*/
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/*
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This file is part of VIPS.
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VIPS is free software; you can redistribute it and/or modify
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it under the terms of the GNU Lesser General Public License as published by
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the Free Software Foundation; either version 2 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
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02110-1301 USA
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*/
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/*
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These files are distributed with VIPS - http://www.vips.ecs.soton.ac.uk
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*/
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#ifdef HAVE_CONFIG_H
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#include <config.h>
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#endif /*HAVE_CONFIG_H*/
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#include <glib/gi18n-lib.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <vips/vips.h>
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#include "pconversion.h"
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typedef struct _VipsSubsample {
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VipsConversion parent_instance;
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VipsImage *in;
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int xfac;
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int yfac;
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gboolean point;
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} VipsSubsample;
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typedef VipsConversionClass VipsSubsampleClass;
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G_DEFINE_TYPE( VipsSubsample, vips_subsample, VIPS_TYPE_CONVERSION );
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/* Maximum width of input we ask for.
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*/
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#define VIPS_MAX_WIDTH (100)
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/* Subsample a VipsRegion. We fetch in VIPS_MAX_WIDTH pixel-wide strips,
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* left-to-right across the input.
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*/
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static int
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vips_subsample_line_gen( VipsRegion *or,
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void *seq, void *a, void *b, gboolean *stop )
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{
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VipsRegion *ir = (VipsRegion *) seq;
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VipsSubsample *subsample = (VipsSubsample *) b;
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VipsImage *in = (VipsImage *) a;
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VipsRect *r = &or->valid;
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int le = r->left;
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int ri = VIPS_RECT_RIGHT( r );
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int to = r->top;
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int bo = VIPS_RECT_BOTTOM( r );
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int ps = VIPS_IMAGE_SIZEOF_PEL( in );
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int owidth = VIPS_MAX_WIDTH / subsample->xfac;
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VipsRect s;
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int x, y;
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int z, k;
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/* Loop down the region.
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*/
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for( y = to; y < bo; y++ ) {
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VipsPel *q = VIPS_REGION_ADDR( or, le, y );
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VipsPel *p;
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/* Loop across the region, in owidth sized pieces.
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*/
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for( x = le; x < ri; x += owidth ) {
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/* How many pixels do we make this time?
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*/
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int ow = VIPS_MIN( owidth, ri - x );
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/* Ask for this many from input ... can save a
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* little here!
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*/
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int iw = ow * subsample->xfac - (subsample->xfac - 1);
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/* Ask for input.
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*/
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s.left = x * subsample->xfac;
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s.top = y * subsample->yfac;
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s.width = iw;
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s.height = 1;
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if( vips_region_prepare( ir, &s ) )
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return( -1 );
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/* Append new pels to output.
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*/
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p = VIPS_REGION_ADDR( ir, s.left, s.top );
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for( z = 0; z < ow; z++ ) {
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for( k = 0; k < ps; k++ )
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q[k] = p[k];
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q += ps;
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p += ps * subsample->xfac;
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}
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}
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}
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return( 0 );
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}
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/* Fetch one pixel at a time ... good for very large shrinks.
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*/
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static int
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vips_subsample_point_gen( VipsRegion *or,
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void *seq, void *a, void *b, gboolean *stop )
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{
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VipsRegion *ir = (VipsRegion *) seq;
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VipsSubsample *subsample = (VipsSubsample *) b;
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VipsImage *in = (VipsImage *) a;
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VipsRect *r = &or->valid;
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int le = r->left;
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int ri = VIPS_RECT_RIGHT( r );
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int to = r->top;
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int bo = VIPS_RECT_BOTTOM(r);
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int ps = VIPS_IMAGE_SIZEOF_PEL( in );
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VipsRect s;
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int x, y;
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int k;
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/* Loop down the region.
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*/
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for( y = to; y < bo; y++ ) {
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VipsPel *q = VIPS_REGION_ADDR( or, le, y );
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VipsPel *p;
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/* Loop across the region, in owidth sized pieces.
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*/
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for( x = le; x < ri; x++ ) {
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/* Ask for input.
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*/
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s.left = x * subsample->xfac;
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s.top = y * subsample->yfac;
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s.width = 1;
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s.height = 1;
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if( vips_region_prepare( ir, &s ) )
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return( -1 );
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/* Append new pels to output.
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*/
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p = VIPS_REGION_ADDR( ir, s.left, s.top );
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for( k = 0; k < ps; k++ )
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q[k] = p[k];
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q += ps;
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}
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}
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return( 0 );
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}
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static int
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vips_subsample_build( VipsObject *object )
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{
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VipsObjectClass *class = VIPS_OBJECT_GET_CLASS( object );
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VipsConversion *conversion = VIPS_CONVERSION( object );
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VipsSubsample *subsample = (VipsSubsample *) object;
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VipsGenerateFn subsample_fn;
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if( VIPS_OBJECT_CLASS( vips_subsample_parent_class )->build( object ) )
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return( -1 );
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g_assert( subsample->xfac > 0 );
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g_assert( subsample->yfac > 0 );
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if( subsample->xfac == 1 &&
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subsample->yfac == 1 )
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return( vips_image_write( subsample->in, conversion->out ) );
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if( vips_image_pio_input( subsample->in ) ||
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vips_check_coding_known( class->nickname, subsample->in ) )
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return( -1 );
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/* Set demand hints. We want THINSTRIP, as we will be demanding a
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* large area of input for each output line.
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*/
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if( vips_image_pipelinev( conversion->out,
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VIPS_DEMAND_STYLE_THINSTRIP, subsample->in, NULL ) )
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return( -1 );
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/* Prepare output. Note: we round the output width down!
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*/
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conversion->out->Xsize = subsample->in->Xsize / subsample->xfac;
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conversion->out->Ysize = subsample->in->Ysize / subsample->yfac;
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conversion->out->Xres = subsample->in->Xres / subsample->xfac;
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conversion->out->Yres = subsample->in->Yres / subsample->yfac;
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if( conversion->out->Xsize <= 0 ||
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conversion->out->Ysize <= 0 ) {
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vips_error( class->nickname,
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"%s", _( "image has shrunk to nothing" ) );
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return( -1 );
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}
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/* Generate! If this is a very large shrink, then it's probably faster
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* to do it a pixel at a time.
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*/
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if( subsample->point ||
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subsample->xfac > 10 )
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subsample_fn = vips_subsample_point_gen;
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else
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subsample_fn = vips_subsample_line_gen;
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if( vips_image_generate( conversion->out,
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vips_start_one, subsample_fn, vips_stop_one,
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subsample->in, subsample ) )
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return( -1 );
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return( 0 );
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}
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static void
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vips_subsample_class_init( VipsSubsampleClass *class )
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{
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GObjectClass *gobject_class = G_OBJECT_CLASS( class );
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VipsObjectClass *vobject_class = VIPS_OBJECT_CLASS( class );
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gobject_class->set_property = vips_object_set_property;
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gobject_class->get_property = vips_object_get_property;
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vobject_class->nickname = "subsample";
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vobject_class->description = _( "subsample an image" );
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vobject_class->build = vips_subsample_build;
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/* We don't work well as sequential: we can easily skip the first few
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* scanlines, and that confuses vips_sequential().
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*/
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VIPS_ARG_IMAGE( class, "input", 1,
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_( "Input" ),
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_( "Input image" ),
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VIPS_ARGUMENT_REQUIRED_INPUT,
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G_STRUCT_OFFSET( VipsSubsample, in ) );
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VIPS_ARG_INT( class, "xfac", 3,
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_( "Xfac" ),
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_( "Horizontal subsample factor" ),
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VIPS_ARGUMENT_REQUIRED_INPUT,
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G_STRUCT_OFFSET( VipsSubsample, xfac ),
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1, VIPS_MAX_COORD, 1 );
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VIPS_ARG_INT( class, "yfac", 4,
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_( "Yfac" ),
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_( "Vertical subsample factor" ),
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VIPS_ARGUMENT_REQUIRED_INPUT,
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G_STRUCT_OFFSET( VipsSubsample, yfac ),
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1, VIPS_MAX_COORD, 1 );
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VIPS_ARG_BOOL( class, "point", 5,
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_( "Point" ),
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_( "Point sample" ),
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VIPS_ARGUMENT_OPTIONAL_INPUT,
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G_STRUCT_OFFSET( VipsSubsample, point ),
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FALSE );
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}
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static void
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vips_subsample_init( VipsSubsample *subsample )
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{
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}
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/**
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* vips_subsample: (method)
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* @in: input image
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* @out: (out): output image
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* @xfac: horizontal shrink factor
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* @yfac: vertical shrink factor
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* @...: %NULL-terminated list of optional named arguments
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*
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* Optional arguments:
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*
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* * @point: turn on point sample mode
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*
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* Subsample an image by an integer fraction. This is fast, nearest-neighbour
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* shrink.
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*
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* For small horizontal shrinks, this operation will fetch lines of pixels
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* from @in and then subsample that line. For large shrinks it will fetch
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* single pixels.
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*
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* If @point is set, @in will always be sampled in points. This can be faster
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* if the previous operations in the pipeline are very slow.
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*
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* See also: vips_affine(), vips_shrink(), vips_zoom().
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*
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* Returns: 0 on success, -1 on error.
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*/
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int
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vips_subsample( VipsImage *in, VipsImage **out, int xfac, int yfac, ... )
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{
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va_list ap;
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int result;
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va_start( ap, yfac );
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result = vips_call_split( "subsample", ap, in, out, xfac, yfac );
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va_end( ap );
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return( result );
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}
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