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/* Raise an image to a gamma factor
*
* Copyright: 1990, N. Dessipris.
*
* Written on: 19/07/1990
* Modified on:
* 19/6/95 JC
* - redone as library function
* 23/3/10
* - gtkdoc
* - 16 bit as well
* 1/8/13
* - redone as a class
* 11/11/13
* - any format
* - calculate pow(1/exp) rather than pow(exp) to be consistent with
* other packages
*/
/*
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
*/
#ifdef HAVE_CONFIG_H
#include <config.h>
#endif /*HAVE_CONFIG_H*/
#include <vips/intl.h>
#include <math.h>
#include <vips/vips.h>
#include "pconversion.h"
typedef struct _VipsGamma {
VipsConversion parent_instance;
VipsImage *in;
double exponent;
} VipsGamma;
typedef VipsConversionClass VipsGammaClass;
G_DEFINE_TYPE( VipsGamma, vips_gamma, VIPS_TYPE_CONVERSION );
/* For each input format, what we normalise the pow() about.
*/
static double vips_gamma_maxval[10] = {
/* UC */ UCHAR_MAX,
/* C */ SCHAR_MAX,
/* US */ USHRT_MAX,
/* S */ SHRT_MAX,
/* UI */ UINT_MAX,
/* I */ INT_MAX,
/* F */ 1.0,
/* X */ 1.0,
/* D */ 1.0,
/* DX */ 1.0
};
static int
vips_gamma_build( VipsObject *object )
{
VipsConversion *conversion = VIPS_CONVERSION( object );
VipsGamma *gamma = (VipsGamma *) object;
VipsImage **t = (VipsImage **) vips_object_local_array( object, 5 );
VipsImage *in = gamma->in;
double scale;
if( VIPS_OBJECT_CLASS( vips_gamma_parent_class )->
build( object ) )
return( -1 );
scale = pow( vips_gamma_maxval[in->BandFmt],
1.0 / gamma->exponent ) /
vips_gamma_maxval[in->BandFmt];
if( in->BandFmt == VIPS_FORMAT_UCHAR ||
in->BandFmt == VIPS_FORMAT_USHORT ) {
if( vips_identity( &t[0],
"ushort", in->BandFmt == VIPS_FORMAT_USHORT,
NULL ) ||
vips_pow_const1( t[0], &t[1],
1.0 / gamma->exponent, NULL ) ||
vips_linear1( t[1], &t[2], 1.0 / scale, 0, NULL ) ||
vips_cast( t[2], &t[3], in->BandFmt, NULL ) ||
vips_maplut( in, &t[4], t[3], NULL ) ||
vips_image_write( t[4], conversion->out ) )
return( -1 );
}
else {
if( vips_pow_const1( in, &t[1],
1.0 / gamma->exponent, NULL ) ||
vips_linear1( t[1], &t[2], 1.0 / scale, 0, NULL ) ||
vips_cast( t[2], &t[3], in->BandFmt, NULL ) ||
vips_image_write( t[3], conversion->out ) )
return( -1 );
}
return( 0 );
}
static void
vips_gamma_class_init( VipsGammaClass *class )
{
GObjectClass *gobject_class = G_OBJECT_CLASS( class );
VipsObjectClass *vobject_class = VIPS_OBJECT_CLASS( class );
VipsOperationClass *operation_class = VIPS_OPERATION_CLASS( class );
gobject_class->set_property = vips_object_set_property;
gobject_class->get_property = vips_object_get_property;
vobject_class->nickname = "gamma";
vobject_class->description = _( "gamma an image" );
vobject_class->build = vips_gamma_build;
operation_class->flags = VIPS_OPERATION_SEQUENTIAL_UNBUFFERED;
VIPS_ARG_IMAGE( class, "in", -1,
_( "in" ),
_( "Input image" ),
VIPS_ARGUMENT_REQUIRED_INPUT,
G_STRUCT_OFFSET( VipsGamma, in ) );
VIPS_ARG_DOUBLE( class, "exponent", 0,
_( "exponent" ),
_( "Gamma factor" ),
VIPS_ARGUMENT_OPTIONAL_INPUT,
G_STRUCT_OFFSET( VipsGamma, exponent ),
0.000001, 1000.0, 2.4 );
}
static void
vips_gamma_init( VipsGamma *gamma )
{
gamma->exponent = 1.0 / 2.4;
}
/**
* vips_gamma:
* @in: input image
* @out: output image
* @...: %NULL-terminated list of optional named arguments
*
* Optional arguments:
*
* * @exponent: gamma, default 1.0 / 2.4
*
* Calculate @in ** (1 / @exponent), normalising to the maximum range of the
* input type. For float types use 1.0 as the maximum.
*
* See also: vips_identity(), vips_pow_const1(), vips_maplut()
*
* Returns: 0 on success, -1 on error
*/
int
vips_gamma( VipsImage *in, VipsImage **out, ... )
{
va_list ap;
int result;
va_start( ap, out );
result = vips_call_split( "gamma", ap, in, out );
va_end( ap );
return( result );
}
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