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//
// Lynkeos
// $Id$
//
// Created by Jean-Etienne LAMIAUD on Sun Aug 17 2008.
// Copyright (c) 2008-2019. Jean-Etienne LAMIAUD
//
// This program is free software; you can redistribute it and/or modify
// it under the terms of the GNU 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 General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
//
#include "LynkeosGammaCorrecter.h"
#define K_MAX_NB_OF_CONVERTERS 3
static const double K_LinearExtent = 0.00304;
/*!
* @abstract Gamma converters array
* @discussion contains all living gamma converters, ordered by last use
*/
static NSMutableArray *converters = nil;
static NSLock *convertersLock = nil;
static double gammaCorrected( double v, double exponent, double linearExtent,
double offset, double slope )
{
double res = 0.0;
if ( exponent == 1.0 )
res = v;
else
{
if ( v <= linearExtent )
res = slope * v;
else
{
if ( exponent < 1.0 )
res = (1.0+offset)*pow(v,exponent) - offset;
else
res = pow((v+offset)/(1.0+offset),exponent);
}
}
return res;
}
/*!
* @abstract Private members of the Gamma correcter
*/
@interface LynkeosGammaCorrecter(Private)
//!Change the gamma value of the correcter
- (void) changeGamma:(double)gamma ;
@end
@implementation LynkeosGammaCorrecter(Private)
- (void) changeGamma:(double)gamma
{
NSAssert( _inUse == 0,
@"Trying to change the gamma of a converter while being used" );
double g, a;
if ( _lut != NULL )
free(_lut );
_lut = NULL;
_gamma = gamma;
_exponent = 1.0/gamma;
// For gamma < 1, we will use 1/slope and apply offset to the input
if ( gamma < 1.0 )
g = 1.0/gamma;
else
g = gamma;
_offset = (1.0 - g)/(g*(1.0 - 1.0/pow(K_LinearExtent,1.0/g))-1);
a = (1.0 + _offset)/g*pow(K_LinearExtent,1.0/g-1.0);
if ( gamma < 1.0 )
{
_slope = 1.0/a;
_linearExtent = K_LinearExtent/a;
}
else
{
_slope = a;
_linearExtent = K_LinearExtent;
}
// Prepare a LUT with these settings
if ( gamma > 1.0 )
_lutSize = (u_long)(256.0*_slope + 0.5);
else
_lutSize = (u_long)(1.0/(1.0
- (1.0+_offset)*pow(255.0/256.0,_exponent)
+ _offset) + 0.5);
_lut = (u_char*)malloc( _lutSize*sizeof(u_char) );
NSAssert1( _lut != NULL, @"Failed to allocate a %ld element gamma LUT",
_lutSize );
u_long i;
for( i = 0; i < _lutSize; i++ )
{
double v = gammaCorrected( (double)i/(double)_lutSize,
_exponent, _linearExtent,
_offset, _slope ) * 256.0;
if ( v < 256.0 )
_lut[i] = (u_char)(v);
else
_lut[i] = 255;
}
}
@end
@implementation LynkeosGammaCorrecter
+ (void) initialize
{
converters = [[NSMutableArray alloc] initWithCapacity:K_MAX_NB_OF_CONVERTERS];
convertersLock = [[NSLock alloc] init];
}
- (id) init
{
if ( (self = [super init]) != nil )
{
_gamma = 1.0;
_exponent = 1.0;
_linearExtent = 0.0;
_offset = 0.0;
_slope = 1.0;
_lut = NULL;
_lutSize = 0;
_inUse = 0;
}
return( self );
}
- (void) dealloc
{
if ( _lut != NULL )
free( _lut );
[super dealloc];
}
+ (LynkeosGammaCorrecter*) getCorrecterForGamma:(double)gamma
{
[convertersLock lock];
const NSUInteger nb = [converters count];
LynkeosGammaCorrecter *c, *theCorrecter;
NSInteger i, theCorrecterIndex = NSNotFound;
theCorrecter = nil;
for( i = 0; i < (int)nb && theCorrecter == nil; i++ )
{
c = [converters objectAtIndex:i];
if ( c->_gamma == gamma )
{
// We found it, extract it from the array (it will be put back in front)
theCorrecter = c;
theCorrecterIndex = i;
if (theCorrecterIndex != 0)
[converters removeObject:c];
}
}
if ( theCorrecter == nil )
{
// No matching converter found, either reuse the last free one,
// or create a new
if ( nb < K_MAX_NB_OF_CONVERTERS )
theCorrecter = [[self alloc] init];
else
{
for( i = (int)(nb-1); i>= 0 && theCorrecter == nil; i-- )
{
c = [converters objectAtIndex:i];
if ( c->_inUse == 0 )
{
theCorrecter = c;
theCorrecterIndex = i;
if (theCorrecterIndex != 0)
[converters removeObject:c];
}
}
}
if (theCorrecter == nil)
{
[convertersLock unlock];
NSAssert( false, @"Too much gamma converters in use" );
}
[theCorrecter changeGamma:gamma];
}
if (theCorrecterIndex != 0)
[converters insertObject:theCorrecter atIndex:0];
theCorrecter->_inUse++;
[convertersLock unlock];
return( theCorrecter );
}
- (void) releaseCorrecter
{
if ( _inUse == 0 )
NSLog( @"Attempt to release a free gamma converter" );
else
_inUse--;
}
@end
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