186 lines
3.9 KiB
C
186 lines
3.9 KiB
C
/* @(#) Turn XYZ to Lab colourspace.
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* @(#)
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* @(#) Usage:
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* @(#) im_XYZ2Lab( imagein, imageout )
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* @(#) IMAGE *imagein, *imageout;
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* @(#)
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* @(#) Float in, float out.
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* @(#)
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* @(#) Returns: -1 on error, else 0
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* Modifed:
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* 16/11/94 JC
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* - uses im_wrapone()
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* - in-line conversion
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* 27/1/03 JC
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* - swapped cbrt() for pow(), more portable
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* 12/11/04
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* - swapped pow() for cbrt() again, pow() is insanely slow on win32
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* - added a configure test for cbrt().
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* 23/11/04
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* - use a large LUT instead, about 5x faster
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* 23/11/06
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* - ahem, build the LUT outside the eval thread
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*/
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/*
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This file is part of VIPS.
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VIPS is free software; you can redistribute it and/or modify
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it under the terms of the GNU Lesser General Public License as published by
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the Free Software Foundation; either version 2 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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*/
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/*
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These files are distributed with VIPS - http://www.vips.ecs.soton.ac.uk
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*/
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#ifdef HAVE_CONFIG_H
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#include <config.h>
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#endif /*HAVE_CONFIG_H*/
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#include <vips/intl.h>
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#include <stdio.h>
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#include <math.h>
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#include <vips/vips.h>
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#ifdef WITH_DMALLOC
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#include <dmalloc.h>
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#endif /*WITH_DMALLOC*/
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#ifndef HAVE_CBRT
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#define cbrt( X ) pow( (X), 1.0 / 3.0 )
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#endif /*!HAVE_CBRT*/
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/* Lookup table size.
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*/
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#define QUANT_ELEMENTS (100000)
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float cbrt_table[QUANT_ELEMENTS];
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void
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imb_XYZ2Lab_tables( void )
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{
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static int built_tables = 0;
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int i;
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if( built_tables )
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return;
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for( i = 0; i < QUANT_ELEMENTS; i++ ) {
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float Y = (double) i / QUANT_ELEMENTS;
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if( Y < 0.008856 )
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cbrt_table[i] = 7.787 * Y + (16.0 / 116.0);
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else
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cbrt_table[i] = cbrt( Y );
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}
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built_tables = 1;
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}
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/* Process a buffer of data.
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*/
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void
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imb_XYZ2Lab( float *p, float *q, int n, im_colour_temperature *temp )
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{
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int x;
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for( x = 0; x < n; x++ ) {
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float nX, nY, nZ;
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int i;
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float f;
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float cbx, cby, cbz;
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nX = QUANT_ELEMENTS * p[0] / temp->X0;
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nY = QUANT_ELEMENTS * p[1] / temp->Y0;
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nZ = QUANT_ELEMENTS * p[2] / temp->Z0;
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p += 3;
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i = (int) nX;
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if( i < 0 )
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i = 0;
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if( i > QUANT_ELEMENTS - 2 )
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i = QUANT_ELEMENTS - 2;
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f = nX - i;
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cbx = cbrt_table[i] + f * (cbrt_table[i + 1] - cbrt_table[i]);
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i = (int) nY;
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if( i < 0 )
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i = 0;
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if( i > QUANT_ELEMENTS - 2 )
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i = QUANT_ELEMENTS - 2;
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f = nY - i;
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cby = cbrt_table[i] + f * (cbrt_table[i + 1] - cbrt_table[i]);
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i = (int) nZ;
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if( i < 0 )
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i = 0;
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if( i > QUANT_ELEMENTS - 2 )
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i = QUANT_ELEMENTS - 2;
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f = nZ - i;
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cbz = cbrt_table[i] + f * (cbrt_table[i + 1] - cbrt_table[i]);
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q[0] = 116.0 * cby - 16.0;
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q[1] = 500.0 * (cbx - cby);
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q[2] = 200.0 * (cby - cbz);
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q += 3;
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}
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}
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int
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im_XYZ2Lab_temp( IMAGE *in, IMAGE *out,
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double X0, double Y0, double Z0 )
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{
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im_colour_temperature *temp = IM_NEW( out, im_colour_temperature );
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/* Check input image.
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*/
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if( !temp )
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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_errormsg( "im_XYZ2Lab: 3-band uncoded float only" );
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return( -1 );
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}
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/* Prepare the output image
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*/
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if( im_cp_desc( out, in) )
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return( -1 );
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out->Type = IM_TYPE_LAB;
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/* Do the processing.
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*/
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imb_XYZ2Lab_tables();
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temp->X0 = X0;
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temp->Y0 = Y0;
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temp->Z0 = Z0;
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if( im_wrapone( in, out,
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(im_wrapone_fn) imb_XYZ2Lab, temp, NULL ) )
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return( -1 );
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return( 0 );
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}
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int
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im_XYZ2Lab( IMAGE *in, IMAGE *out )
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{
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return( im_XYZ2Lab_temp( in, out, IM_D65_X0, IM_D65_Y0, IM_D65_Z0 ) );
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}
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