libvips/libsrc/colour/im_Lab2XYZ.c

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/* @(#) Turn Lab to XYZ colourspace.
* @(#)
* @(#) Usage:
* @(#) im_Lab2XYZ( imagein, imageout )
* @(#) IMAGE *imagein, *imageout;
* @(#)
* @(#) Float in, float out.
* @(#)
* @(#) Returns: -1 on error, else 0
* Modified:
* 15/11/94 JC
* - ANSIfied
* - sets Type of output
* - better error messages
* 16/11/94 JC
* - partialed
* - in-line conversion
* 8/2/95 JC
* - new im_wrapone function
*/
/*
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>
#ifdef WITH_DMALLOC
#include <dmalloc.h>
#endif /*WITH_DMALLOC*/
/* Process a buffer of data.
*/
void
imb_Lab2XYZ( float *p, float *q, int n, im_colour_temperature *temp )
{
int x;
for( x = 0; x < n; x++ ) {
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float L, a, b;
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float X, Y, Z;
double cby, tmp;
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L = p[0];
a = p[1];
b = p[2];
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p += 3;
if( L < 8.0 ) {
Y = (L * temp->Y0) / 903.3;
cby = 7.787 * (Y / temp->Y0) + 16.0 / 116.0;
}
else {
cby = (L + 16.0) / 116.0;
Y = temp->Y0 * cby * cby * cby;
}
tmp = a / 500.0 + cby;
if( tmp < 0.2069 )
X = temp->X0 * (tmp - 0.13793) / 7.787;
else
X = temp->X0 * tmp * tmp * tmp;
tmp = cby - b / 200.0;
if( tmp < 0.2069 )
Z = temp->Z0 * (tmp - 0.13793) / 7.787;
else
Z = temp->Z0 * tmp * tmp * tmp;
/* Write.
*/
q[0] = X;
q[1] = Y;
q[2] = Z;
q += 3;
}
}
int
im_Lab2XYZ_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_Lab2XYZ", "%s", _( "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_XYZ;
/* Process!
*/
temp->X0 = X0;
temp->Y0 = Y0;
temp->Z0 = Z0;
if( im_wrapone( in, out,
(im_wrapone_fn) imb_Lab2XYZ, temp, NULL ) )
return( -1 );
return( 0 );
}
int
im_Lab2XYZ( IMAGE *in, IMAGE *out )
{
return( im_Lab2XYZ_temp( in, out, IM_D65_X0, IM_D65_Y0, IM_D65_Z0 ) );
}