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/* im_scale
*
* Author: John Cupitt
* Written on: 22/4/93
* Modified on:
* 30/6/93 JC
* - adapted for partial v2
* - ANSI
* 31/8/93 JC
* - calculation of offset now includes scale
* 8/5/06
* - set Type on output too
* 16/10/06
* - what? no, don't set Type, useful to be able to scale histograms, for
* example
* 1/2/10
* - gtkdoc
* 30/5/13
* - redo as a class
* - add log scale and exponent as an option
* 14/1/14
* - use linear uchar mode
* 14/7/14
* - round to nearest on uchar output
*/
/*
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 <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <vips/vips.h>
#include "pconversion.h"
typedef struct _VipsScale {
VipsConversion parent_instance;
VipsImage *in;
gboolean log;
double exp;
} VipsScale;
typedef VipsConversionClass VipsScaleClass;
G_DEFINE_TYPE( VipsScale, vips_scale, VIPS_TYPE_CONVERSION );
static int
vips_scale_build( VipsObject *object )
{
VipsConversion *conversion = VIPS_CONVERSION( object );
VipsScale *scale = (VipsScale *) object;
VipsImage **t = (VipsImage **) vips_object_local_array( object, 7 );
double mx;
double mn;
if( VIPS_OBJECT_CLASS( vips_scale_parent_class )->build( object ) )
return( -1 );
if( vips_stats( scale->in, &t[0], NULL ) )
return( -1 );
mn = *VIPS_MATRIX( t[0], 0, 0 );
mx = *VIPS_MATRIX( t[0], 1, 0 );
if( mn == mx ) {
/* Range of zero: just return black.
*/
if( vips_black( &t[1], scale->in->Xsize, scale->in->Ysize,
"bands", scale->in->Bands,
NULL ) ||
vips_image_write( t[1], conversion->out ) )
return( -1 );
}
else if( scale->log ) {
double f = 255.0 / log10( 1.0 + pow( mx, scale->exp ) );
if( vips_pow_const1( scale->in, &t[2], scale->exp, NULL ) ||
vips_linear1( t[2], &t[3], 1.0, 1.0, NULL ) ||
vips_log10( t[3], &t[4], NULL ) ||
vips_linear1( t[4], &t[5], f, 0.0,
"uchar", TRUE,
NULL ) ||
vips_image_write( t[5], conversion->out ) )
return( -1 );
}
else {
double f = 255.0 / (mx - mn);
/* Add .5 to get round-to-nearest.
*/
double a = -(mn * f) + 0.5;
if( vips_linear1( scale->in, &t[2], f, a,
"uchar", TRUE,
NULL ) ||
vips_image_write( t[2], conversion->out ) )
return( -1 );
}
return( 0 );
}
static void
vips_scale_class_init( VipsScaleClass *class )
{
GObjectClass *gobject_class = G_OBJECT_CLASS( class );
VipsObjectClass *vobject_class = VIPS_OBJECT_CLASS( class );
gobject_class->set_property = vips_object_set_property;
gobject_class->get_property = vips_object_get_property;
vobject_class->nickname = "scale";
vobject_class->description = _( "scale an image to uchar" );
vobject_class->build = vips_scale_build;
VIPS_ARG_IMAGE( class, "in", 1,
_( "Input" ),
_( "Input image" ),
VIPS_ARGUMENT_REQUIRED_INPUT,
G_STRUCT_OFFSET( VipsScale, in ) );
VIPS_ARG_BOOL( class, "log", 3,
_( "Log" ),
_( "Log scale" ),
VIPS_ARGUMENT_OPTIONAL_INPUT,
G_STRUCT_OFFSET( VipsScale, log ),
FALSE );
VIPS_ARG_DOUBLE( class, "exp", 3,
_( "Exponent" ),
_( "Exponent for log scale" ),
VIPS_ARGUMENT_OPTIONAL_INPUT,
G_STRUCT_OFFSET( VipsScale, exp ),
0.00001, 10000, 0.25 );
}
static void
vips_scale_init( VipsScale *scale )
{
scale->exp = 0.25;
}
/**
* vips_scale:
* @in: input image
* @out: output image
* @...: %NULL-terminated list of optional named arguments
*
* Optional arguments:
*
* * @log: log scale pixels
* * @exp: exponent for log scale
*
* Search the image for the maximum and minimum value, then return the image
* as unsigned 8-bit, scaled so that the maximum value is 255 and the
* minimum is zero.
*
* If @log is set, transform with log10(1.0 + pow(x, @exp)) + .5,
* then scale so max == 255. By default, @exp is 0.25.
*
* See also: vips_cast().
*
* Returns: 0 on success, -1 on error
*/
int
vips_scale( VipsImage *in, VipsImage **out, ... )
{
va_list ap;
int result;
va_start( ap, out );
result = vips_call_split( "scale", ap, in, out );
va_end( ap );
return( result );
}
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