add an experimental premultiply operation
This commit is contained in:
John Cupitt
parent
90a47b0cad
commit
66c51b7d23
8
TODO
8
TODO
@ -1,3 +1,11 @@
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- does flatten work with float?
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looks like it has some confusion with flatten->in and in
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change rules for alphha max ... copy the premultiply convention of using
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Type to set the range
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- are the mosaic functions calling vips_fastcor()? it must be very slow
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@ -9,7 +9,7 @@
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<bookinfo>
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<title>VIPS Reference Manual</title>
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<releaseinfo>
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For VIPS 8.0.2.
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For VIPS 8.1.0.
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The latest version of this documentation can be found on the
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<ulink role="online-location"
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url="http://www.vips.ecs.soton.ac.uk/index.php?title=Documentation">VIPS website</ulink>.
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@ -7,6 +7,7 @@ libconversion_la_SOURCES = \
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gamma.c \
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sequential.c \
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flatten.c \
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premultiply.c \
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cache.c \
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copy.c \
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embed.c \
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@ -238,6 +238,7 @@ vips_conversion_operation_init( void )
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extern GType vips_recomb_get_type( void );
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extern GType vips_bandmean_get_type( void );
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extern GType vips_flatten_get_type( void );
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extern GType vips_premultiply_get_type( void );
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extern GType vips_bandbool_get_type( void );
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extern GType vips_gaussnoise_get_type( void );
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extern GType vips_grid_get_type( void );
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@ -277,6 +278,7 @@ vips_conversion_operation_init( void )
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vips_recomb_get_type();
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vips_bandmean_get_type();
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vips_flatten_get_type();
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vips_premultiply_get_type();
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vips_bandbool_get_type();
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vips_gaussnoise_get_type();
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vips_grid_get_type();
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365
libvips/conversion/premultiply.c
Normal file
365
libvips/conversion/premultiply.c
Normal file
@ -0,0 +1,365 @@
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/* premultiply and unpremultiply alpha
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*
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* Author: John Cupitt
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* Written on: 7/5/15
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*
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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 _VipsPremultiply {
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VipsConversion parent_instance;
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VipsImage *in;
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/* Set for the inverse transform (divide, or unpremultiply).
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*/
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gboolean unpremultiply;
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} VipsPremultiply;
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typedef VipsConversionClass VipsPremultiplyClass;
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G_DEFINE_TYPE( VipsPremultiply, vips_premultiply, VIPS_TYPE_CONVERSION );
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/* Pre and unpre ops.
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*/
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#define PRE_MULTIPLY( Q, P ) { \
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(Q) = (P) * nalpha; \
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}
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#define UNPRE_MULTIPLY( Q, P ) { \
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if( clip_alpha == 0 ) \
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(Q) = 0.0; \
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else \
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(Q) = (P) / nalpha; \
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}
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/* Premultiply a greyscale (two band) image.
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*/
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#define PRE_GREY( IN, OUT, OP ) { \
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IN * restrict p = (IN *) in; \
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OUT * restrict q = (OUT *) out; \
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\
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for( x = 0; x < width; x++ ) { \
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IN alpha = p[1]; \
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int clip_alpha = VIPS_CLIP( 0, alpha, max_value ); \
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double nalpha = clip_alpha / max_value; \
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\
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OP( q[0], p[0] ); \
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q[1] = alpha; \
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\
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p += 2; \
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q += 2; \
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} \
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}
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/* Premultiply an RGB (four band) image.
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*/
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#define PRE_RGB( IN, OUT, OP ) { \
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IN * restrict p = (IN *) in; \
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OUT * restrict q = (OUT *) out; \
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\
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for( x = 0; x < width; x++ ) { \
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IN alpha = p[3]; \
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int clip_alpha = VIPS_CLIP( 0, alpha, max_value ); \
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double nalpha = clip_alpha / max_value; \
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\
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OP( q[0], p[0] ); \
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OP( q[1], p[1] ); \
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OP( q[2], p[2] ); \
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q[3] = alpha; \
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\
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p += 4; \
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q += 4; \
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} \
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}
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/* Premultiply a CMYK (five band) image.
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*/
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#define PRE_CMYK( IN, OUT, OP ) { \
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IN * restrict p = (IN *) in; \
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OUT * restrict q = (OUT *) out; \
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\
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for( x = 0; x < width; x++ ) { \
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IN alpha = p[4]; \
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int clip_alpha = VIPS_CLIP( 0, alpha, max_value ); \
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double nalpha = clip_alpha / max_value; \
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\
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OP( q[0], p[0] ); \
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OP( q[1], p[1] ); \
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OP( q[2], p[2] ); \
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OP( q[3], p[3] ); \
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q[4] = alpha; \
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\
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p += 5; \
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q += 5; \
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} \
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}
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#define PRE_OP( IN, OUT, OP ) { \
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if( bands == 2 ) { \
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PRE_GREY( IN, OUT, OP ); \
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} \
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else if( bands == 4 ) { \
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PRE_RGB( IN, OUT, OP ); \
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} \
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else { \
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PRE_CMYK( IN, OUT, OP ); \
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} \
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}
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#define PRE( IN, OUT ) { \
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if( premultiply->unpremultiply ) { \
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PRE_OP( IN, OUT, UNPRE_MULTIPLY ); \
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} \
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else { \
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PRE_OP( IN, OUT, PRE_MULTIPLY ); \
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} \
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}
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static int
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vips_premultiply_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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VipsImage *im = ir->im;
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VipsPremultiply *premultiply = (VipsPremultiply *) b;
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VipsRect *r = &or->valid;
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int width = r->width;
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int bands = im->Bands;
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int max_value;
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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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if( im->Type == VIPS_INTERPRETATION_GREY16 ||
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im->Type == VIPS_INTERPRETATION_RGB16 )
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max_value = 65535;
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else
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max_value = 255;
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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( im->BandFmt ) {
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case VIPS_FORMAT_UCHAR:
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PRE( unsigned char, float );
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break;
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case VIPS_FORMAT_CHAR:
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PRE( signed char, float );
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break;
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case VIPS_FORMAT_USHORT:
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PRE( unsigned short, float );
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break;
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case VIPS_FORMAT_SHORT:
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PRE( signed short, float );
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break;
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case VIPS_FORMAT_UINT:
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PRE( unsigned int, float );
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break;
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case VIPS_FORMAT_INT:
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PRE( signed int, float );
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break;
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case VIPS_FORMAT_FLOAT:
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PRE( float, float );
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break;
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case VIPS_FORMAT_DOUBLE:
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PRE( double, 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_premultiply_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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VipsPremultiply *premultiply = (VipsPremultiply *) object;
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VipsImage **t = (VipsImage **) vips_object_local_array( object, 1 );
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VipsImage *in;
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if( VIPS_OBJECT_CLASS( vips_premultiply_parent_class )->
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build( object ) )
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return( -1 );
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in = premultiply->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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in->Bands == 3 ||
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(in->Bands == 4 &&
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in->Type == VIPS_INTERPRETATION_CMYK) )
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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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if( in->BandFmt == VIPS_FORMAT_DOUBLE )
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conversion->out->BandFmt = VIPS_FORMAT_DOUBLE;
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else
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conversion->out->BandFmt = VIPS_FORMAT_FLOAT;
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if( vips_image_generate( conversion->out,
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vips_start_one, vips_premultiply_gen, vips_stop_one,
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in, premultiply ) )
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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_premultiply_class_init( VipsPremultiplyClass *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_premultiply_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 = "premultiply";
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vobject_class->description = _( "premultiply image alpha" );
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vobject_class->build = vips_premultiply_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( VipsPremultiply, in ) );
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VIPS_ARG_BOOL( class, "unpremultiply", 2,
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_( "Unpremultiply" ),
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_( "Reverse transform" ),
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VIPS_ARGUMENT_OPTIONAL_INPUT,
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G_STRUCT_OFFSET( VipsPremultiply, unpremultiply ),
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FALSE );
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}
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static void
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vips_premultiply_init( VipsPremultiply *premultiply )
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{
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}
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/**
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* vips_premultiply:
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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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* @unpremultiply: %gboolean, set this to reverse the transform
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*
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* Premultiplies any alpha channel. If @in is an 8-bit RGBA image, @out will
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* also have four bands, where:
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*
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* |[
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* n = in[3] / 255; // normalised alpha
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* out = [in[0] * n, in[1] * n, in[2] * n, in[3]];
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* |]
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*
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* So the RGB bands are scaled by alpha, alpha is untouched. The result is
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* always #VIPS_FORMAT_FLOAT. If you set @unpremultiply, the inverse operation
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* is performed, so RGB are divided by normalised alpha. If there is no alpha,
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* the image is passed through unaltered.
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*
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* The operation works for 1 - 5 band images, from greyscale to CMYKA. 16-bit
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* unsigned int image are assumed to have a 16-bit alpha, all other images are
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* expected to have 0 - 255 alpha.
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*
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* See also: vips_flatten().
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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_premultiply( 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( "premultiply", ap, in, out );
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va_end( ap );
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return( result );
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}
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@ -186,6 +186,8 @@ int vips_ifthenelse( VipsImage *cond, VipsImage *in1, VipsImage *in2,
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__attribute__((sentinel));
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int vips_flatten( VipsImage *in, VipsImage **out, ... )
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__attribute__((sentinel));
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int vips_premultiply( VipsImage *in, VipsImage **out, ... )
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__attribute__((sentinel));
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int vips_falsecolour( VipsImage *in, VipsImage **out, ... )
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__attribute__((sentinel));
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Reference in New Issue
Block a user