446 lines
9.9 KiB
C
446 lines
9.9 KiB
C
/* flatten the alpha out of an image, replacing it with a constant background
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*
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* Author: John Cupitt
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* Written on: 18/6/12
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*
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* 4/1/14
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* - better rounding
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* 9/5/15
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* - add max_alpha to match vips_premultiply() etc.
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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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/*
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#define VIPS_DEBUG
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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 <vips/intl.h>
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#include <stdio.h>
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#include <string.h>
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#include <stdlib.h>
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#include <math.h>
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#include <vips/vips.h>
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#include <vips/internal.h>
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#include <vips/debug.h>
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#include "pconversion.h"
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typedef struct _VipsFlatten {
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VipsConversion parent_instance;
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VipsImage *in;
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/* Background colour.
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*/
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VipsArrayDouble *background;
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/* The [double] converted to the input image format.
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*/
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VipsPel *ink;
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/* Use this to scale alpha to 0 - 1.
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*/
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double max_alpha;
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} VipsFlatten;
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typedef VipsConversionClass VipsFlattenClass;
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G_DEFINE_TYPE( VipsFlatten, vips_flatten, VIPS_TYPE_CONVERSION );
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/* Flatten with black background.
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*/
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#define VIPS_FLATTEN_BLACK( TYPE ) { \
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TYPE * restrict p = (TYPE *) in; \
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TYPE * restrict q = (TYPE *) out; \
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\
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for( x = 0; x < width; x++ ) { \
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TYPE alpha = p[bands - 1]; \
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int b; \
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\
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for( b = 0; b < bands - 1; b++ ) \
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q[b] = (p[b] * alpha) / max_alpha; \
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\
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p += bands; \
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q += bands - 1; \
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} \
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}
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/* Flatten with any background.
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*/
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#define VIPS_FLATTEN( TYPE ) { \
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TYPE * restrict p = (TYPE *) in; \
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TYPE * restrict q = (TYPE *) out; \
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\
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for( x = 0; x < width; x++ ) { \
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TYPE alpha = p[bands - 1]; \
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TYPE nalpha = max_alpha - alpha; \
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TYPE * restrict bg = (TYPE *) flatten->ink; \
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int b; \
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\
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for( b = 0; b < bands - 1; b++ ) \
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q[b] = (p[b] * alpha) / max_alpha + \
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(bg[b] * nalpha) / max_alpha; \
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\
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p += bands; \
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q += bands - 1; \
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} \
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}
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/* Same, but with float arithmetic. Necessary for int/uint to prevent
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* overflow.
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*/
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#define VIPS_FLATTEN_BLACK_FLOAT( TYPE ) { \
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TYPE * restrict p = (TYPE *) in; \
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TYPE * restrict q = (TYPE *) out; \
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\
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for( x = 0; x < width; x++ ) { \
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TYPE alpha = p[bands - 1]; \
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int b; \
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\
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for( b = 0; b < bands - 1; b++ ) \
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q[b] = ((double) p[b] * alpha) / max_alpha; \
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\
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p += bands; \
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q += bands - 1; \
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} \
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}
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#define VIPS_FLATTEN_FLOAT( TYPE ) { \
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TYPE * restrict p = (TYPE *) in; \
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TYPE * restrict q = (TYPE *) out; \
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\
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for( x = 0; x < width; x++ ) { \
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TYPE alpha = p[bands - 1]; \
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TYPE nalpha = max_alpha - alpha; \
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TYPE * restrict bg = (TYPE *) flatten->ink; \
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int b; \
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\
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for( b = 0; b < bands - 1; b++ ) \
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q[b] = ((double) p[b] * alpha) / max_alpha + \
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((double) bg[b] * nalpha) / max_alpha; \
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\
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p += bands; \
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q += bands - 1; \
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} \
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}
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static int
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vips_flatten_black_gen( VipsRegion *or, void *vseq, void *a, void *b,
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gboolean *stop )
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{
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VipsRegion *ir = (VipsRegion *) vseq;
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VipsFlatten *flatten = (VipsFlatten *) b;
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VipsRect *r = &or->valid;
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int width = r->width;
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int bands = ir->im->Bands;
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double max_alpha = flatten->max_alpha;
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int x, y;
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if( vips_region_prepare( ir, r ) )
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return( -1 );
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for( y = 0; y < r->height; y++ ) {
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VipsPel *in = VIPS_REGION_ADDR( ir, r->left, r->top + y );
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VipsPel *out = VIPS_REGION_ADDR( or, r->left, r->top + y );
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switch( flatten->in->BandFmt ) {
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case VIPS_FORMAT_UCHAR:
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VIPS_FLATTEN_BLACK( unsigned char );
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break;
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case VIPS_FORMAT_CHAR:
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VIPS_FLATTEN_BLACK( signed char );
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break;
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case VIPS_FORMAT_USHORT:
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VIPS_FLATTEN_BLACK( unsigned short );
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break;
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case VIPS_FORMAT_SHORT:
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VIPS_FLATTEN_BLACK( signed short );
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break;
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case VIPS_FORMAT_UINT:
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VIPS_FLATTEN_BLACK_FLOAT( unsigned int );
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break;
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case VIPS_FORMAT_INT:
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VIPS_FLATTEN_BLACK_FLOAT( signed int );
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break;
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case VIPS_FORMAT_FLOAT:
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VIPS_FLATTEN_BLACK_FLOAT( float );
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break;
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case VIPS_FORMAT_DOUBLE:
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VIPS_FLATTEN_BLACK_FLOAT( double );
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break;
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case VIPS_FORMAT_COMPLEX:
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case VIPS_FORMAT_DPCOMPLEX:
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default:
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g_assert( 0 );
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}
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}
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return( 0 );
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}
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/* Any background.
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*/
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static int
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vips_flatten_gen( VipsRegion *or, void *vseq, void *a, void *b,
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gboolean *stop )
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{
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VipsRegion *ir = (VipsRegion *) vseq;
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VipsFlatten *flatten = (VipsFlatten *) b;
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VipsRect *r = &or->valid;
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int width = r->width;
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int bands = ir->im->Bands;
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double max_alpha = flatten->max_alpha;
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int x, y;
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if( vips_region_prepare( ir, r ) )
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return( -1 );
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for( y = 0; y < r->height; y++ ) {
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VipsPel *in = VIPS_REGION_ADDR( ir, r->left, r->top + y );
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VipsPel *out = VIPS_REGION_ADDR( or, r->left, r->top + y );
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switch( flatten->in->BandFmt ) {
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case VIPS_FORMAT_UCHAR:
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VIPS_FLATTEN( unsigned char );
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break;
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case VIPS_FORMAT_CHAR:
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VIPS_FLATTEN( signed char );
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break;
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case VIPS_FORMAT_USHORT:
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VIPS_FLATTEN( unsigned short );
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break;
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case VIPS_FORMAT_SHORT:
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VIPS_FLATTEN( signed short );
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break;
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case VIPS_FORMAT_UINT:
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VIPS_FLATTEN_FLOAT( unsigned int );
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break;
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case VIPS_FORMAT_INT:
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VIPS_FLATTEN_FLOAT( signed int );
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break;
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case VIPS_FORMAT_FLOAT:
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VIPS_FLATTEN_FLOAT( float );
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break;
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case VIPS_FORMAT_DOUBLE:
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VIPS_FLATTEN_FLOAT( double );
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break;
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case VIPS_FORMAT_COMPLEX:
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case VIPS_FORMAT_DPCOMPLEX:
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default:
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g_assert( 0 );
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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_flatten_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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VipsFlatten *flatten = (VipsFlatten *) object;
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VipsImage **t = (VipsImage **) vips_object_local_array( object, 1 );
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VipsImage *in;
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int i;
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gboolean black;
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if( VIPS_OBJECT_CLASS( vips_flatten_parent_class )->build( object ) )
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return( -1 );
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in = flatten->in;
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if( vips_image_decode( in, &t[0] ) )
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return( -1 );
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in = t[0];
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/* Trivial case: fall back to copy().
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*/
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if( in->Bands == 1 )
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return( vips_image_write( in, conversion->out ) );
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if( vips_check_noncomplex( class->nickname, in ) )
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return( -1 );
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if( vips_image_pipelinev( conversion->out,
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VIPS_DEMAND_STYLE_THINSTRIP, in, NULL ) )
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return( -1 );
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conversion->out->Bands -= 1;
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/* Is the background black? We have a special path for this.
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*/
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black = TRUE;
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for( i = 0; i < VIPS_AREA( flatten->background )->n; i++ )
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if( vips_array_double_get( flatten->background, NULL )[i] !=
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0.0 ) {
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black = FALSE;
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break;
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}
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if( black ) {
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if( vips_image_generate( conversion->out,
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vips_start_one, vips_flatten_black_gen, vips_stop_one,
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in, flatten ) )
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return( -1 );
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}
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else {
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/* Convert the background to the image's format.
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*/
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if( !(flatten->ink = vips__vector_to_ink( class->nickname,
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conversion->out,
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VIPS_AREA( flatten->background )->data, NULL,
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VIPS_AREA( flatten->background )->n )) )
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return( -1 );
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if( vips_image_generate( conversion->out,
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vips_start_one, vips_flatten_gen, vips_stop_one,
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in, flatten ) )
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return( -1 );
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}
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return( 0 );
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}
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static void
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vips_flatten_class_init( VipsFlattenClass *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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VipsOperationClass *operation_class = VIPS_OPERATION_CLASS( class );
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VIPS_DEBUG_MSG( "vips_flatten_class_init\n" );
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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 = "flatten";
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vobject_class->description = _( "flatten alpha out of an image" );
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vobject_class->build = vips_flatten_build;
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operation_class->flags = VIPS_OPERATION_SEQUENTIAL_UNBUFFERED;
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VIPS_ARG_IMAGE( class, "in", 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( VipsFlatten, in ) );
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VIPS_ARG_BOXED( class, "background", 2,
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_( "Background" ),
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_( "Background value" ),
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VIPS_ARGUMENT_OPTIONAL_INPUT,
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G_STRUCT_OFFSET( VipsFlatten, background ),
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VIPS_TYPE_ARRAY_DOUBLE );
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VIPS_ARG_DOUBLE( class, "max_alpha", 115,
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_( "Maximum alpha" ),
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_( "Maximum value of alpha channel" ),
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VIPS_ARGUMENT_OPTIONAL_INPUT,
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G_STRUCT_OFFSET( VipsFlatten, max_alpha ),
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0, 100000000, 255 );
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}
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static void
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vips_flatten_init( VipsFlatten *flatten )
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{
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flatten->background = vips_array_double_newv( 1, 0.0 );
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flatten->max_alpha= 255.0;
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}
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/**
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* vips_flatten:
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* @in: input image
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* @out: output image
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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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* @background: #VipsArrayDouble colour for new pixels
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* @max_alpha: %gdouble, maximum value for alpha
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*
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* Take the last band of @in as an alpha and use it to blend the
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* remaining channels with @background.
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*
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* The alpha channel is 0 - @max_alpha,
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* where 1 means 100% image and 0
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* means 100% background.
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* Non-complex images only.
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* @background defaults to zero (black).
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*
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* @max_alpha has the default value 255. You will need to set this to 65535
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* for images with a 16-bit alpha, or perhaps 1.0 for images with a float
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* alpha.
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*
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* Useful for flattening PNG images to RGB.
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*
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* See also: vips_premultiply(), vips_pngload().
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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_flatten( VipsImage *in, VipsImage **out, ... )
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{
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va_list ap;
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int result;
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va_start( ap, out );
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result = vips_call_split( "flatten", ap, in, out );
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va_end( ap );
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return( result );
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}
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