libvips/libsrc/colour/im_XYZ2Lab.c

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/* @(#) Turn XYZ to Lab colourspace.
* @(#)
* @(#) Usage:
* @(#) im_XYZ2Lab( imagein, imageout )
* @(#) IMAGE *imagein, *imageout;
* @(#)
* @(#) Float in, float out.
* @(#)
* @(#) Returns: -1 on error, else 0
* Modifed:
* 16/11/94 JC
* - uses im_wrapone()
* - in-line conversion
* 27/1/03 JC
* - swapped cbrt() for pow(), more portable
* 12/11/04
* - swapped pow() for cbrt() again, pow() is insanely slow on win32
* - added a configure test for cbrt().
* 23/11/04
* - use a large LUT instead, about 5x faster
* 23/11/06
* - ahem, build the LUT outside the eval thread
*/
/*
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., 59 Temple Place, Suite 330, Boston, MA 02111-1307 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 <math.h>
#include <vips/vips.h>
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#include <vips/internal.h>
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#ifdef WITH_DMALLOC
#include <dmalloc.h>
#endif /*WITH_DMALLOC*/
#ifndef HAVE_CBRT
#define cbrt( X ) pow( (X), 1.0 / 3.0 )
#endif /*!HAVE_CBRT*/
/* Lookup table size.
*/
#define QUANT_ELEMENTS (100000)
float cbrt_table[QUANT_ELEMENTS];
void
imb_XYZ2Lab_tables( void )
{
static int built_tables = 0;
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int was_built;
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int i;
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g_mutex_lock( im__global_lock );
was_built = built_tables;
built_tables = 1;
g_mutex_unlock( im__global_lock );
if( was_built )
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return;
for( i = 0; i < QUANT_ELEMENTS; i++ ) {
float Y = (double) i / QUANT_ELEMENTS;
if( Y < 0.008856 )
cbrt_table[i] = 7.787 * Y + (16.0 / 116.0);
else
cbrt_table[i] = cbrt( Y );
}
}
/* Process a buffer of data.
*/
void
imb_XYZ2Lab( float *p, float *q, int n, im_colour_temperature *temp )
{
int x;
for( x = 0; x < n; x++ ) {
float nX, nY, nZ;
int i;
float f;
float cbx, cby, cbz;
nX = QUANT_ELEMENTS * p[0] / temp->X0;
nY = QUANT_ELEMENTS * p[1] / temp->Y0;
nZ = QUANT_ELEMENTS * p[2] / temp->Z0;
p += 3;
i = (int) nX;
if( i < 0 )
i = 0;
if( i > QUANT_ELEMENTS - 2 )
i = QUANT_ELEMENTS - 2;
f = nX - i;
cbx = cbrt_table[i] + f * (cbrt_table[i + 1] - cbrt_table[i]);
i = (int) nY;
if( i < 0 )
i = 0;
if( i > QUANT_ELEMENTS - 2 )
i = QUANT_ELEMENTS - 2;
f = nY - i;
cby = cbrt_table[i] + f * (cbrt_table[i + 1] - cbrt_table[i]);
i = (int) nZ;
if( i < 0 )
i = 0;
if( i > QUANT_ELEMENTS - 2 )
i = QUANT_ELEMENTS - 2;
f = nZ - i;
cbz = cbrt_table[i] + f * (cbrt_table[i + 1] - cbrt_table[i]);
q[0] = 116.0 * cby - 16.0;
q[1] = 500.0 * (cbx - cby);
q[2] = 200.0 * (cby - cbz);
q += 3;
}
}
int
im_XYZ2Lab_temp( IMAGE *in, IMAGE *out,
double X0, double Y0, double Z0 )
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{
im_colour_temperature *temp;
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/* Check input image.
*/
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if( !(temp = IM_NEW( out, im_colour_temperature )) )
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return( -1 );
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if( in->Bands != 3 ||
in->BandFmt != IM_BANDFMT_FLOAT ||
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in->Coding != IM_CODING_NONE ) {
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im_error( "im_XYZ2Lab", _( "not 3-band uncoded float" ) );
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return( -1 );
}
/* Prepare the output image
*/
if( im_cp_desc( out, in) )
return( -1 );
out->Type = IM_TYPE_LAB;
/* Do the processing.
*/
imb_XYZ2Lab_tables();
temp->X0 = X0;
temp->Y0 = Y0;
temp->Z0 = Z0;
if( im_wrapone( in, out,
(im_wrapone_fn) imb_XYZ2Lab, temp, NULL ) )
return( -1 );
return( 0 );
}
int
im_XYZ2Lab( IMAGE *in, IMAGE *out )
{
return( im_XYZ2Lab_temp( in, out, IM_D65_X0, IM_D65_Y0, IM_D65_Z0 ) );
}