252 lines
5.0 KiB
C
252 lines
5.0 KiB
C
/* LCh2CMC
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*
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* Modified:
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* 2/11/09
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* - gtkdoc
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* 19/9/12
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* - redone as a class
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* 24/9/14
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* - rechecked against original paper, seems OK
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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., 51 Franklin Street, Fifth Floor, Boston, MA
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02110-1301 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 <glib/gi18n-lib.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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#include "pcolour.h"
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typedef VipsColourTransform VipsLCh2CMC;
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typedef VipsColourTransformClass VipsLCh2CMCClass;
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G_DEFINE_TYPE( VipsLCh2CMC, vips_LCh2CMC, VIPS_TYPE_COLOUR_TRANSFORM );
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/* I ordered this paper from the library and it took ages. For reference, the
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* recommended short formula are:
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*
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* Lucs
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* = 1.744 * L, L < 16
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* = (1/l) * (21.75 * ln(L) + 0.3838 * L - 38.54), otherwise
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*
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* Cucs = (l/c) * (0.162 * C + 10.92 * (ln(0.638 + 0.07216 * C)) + 4.907)
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*
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* hucs = h + D * f
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* where
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* D = k4 + k5 * P * | P | ** k6
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* P = cos(k7 * h + k8)
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* f = (C ** 4 / (C ** 4 + 1900)) ** 0.5
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*
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* h k4 k5 k6 k7 k8
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* 0 - 49 133.87 -134.5 -0.924 1.727 340
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* 49 - 110 11.78 -12.7 -0.218 2.120 333
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* 110 - 269.5 13.87 10.93 0.140 1.000 -83
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* 269.5 - 360 0.14 5.23 0.170 1.610 233
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*
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* They have a much more complicated but slightly more accurate formula for
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* hucs. This one is pretty good, simple approximation.
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*/
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/**
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* vips_col_L2Lcmc:
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* @L: CIE L*
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*
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* Calculate Lcmc from L.
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*
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* Returns: Lcmc
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*/
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float
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vips_col_L2Lcmc( float L )
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{
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float Lcmc;
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if( L < 16.0 )
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Lcmc = 1.744 * L;
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else
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Lcmc = 21.75 * log( L ) + 0.3838 * L - 38.54;
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return( Lcmc );
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}
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/**
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* vips_col_C2Ccmc:
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* @C: Chroma
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*
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* Calculate Ccmc from C.
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*
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* Returns: Ccmc.
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*/
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float
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vips_col_C2Ccmc( float C )
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{
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float Ccmc;
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Ccmc = 0.162 * C + 10.92 * log( 0.638 + 0.07216 * C ) + 4.907;
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if( Ccmc < 0 )
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Ccmc = 0;
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return( Ccmc );
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}
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/**
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* vips_col_Ch2hcmc:
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* @C: Chroma
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* @h: Hue (degrees)
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*
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* Calculate hcmc from C and h.
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*
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* Returns: hcmc.
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*/
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float
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vips_col_Ch2hcmc( float C, float h )
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{
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float P, D, f, g;
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float k4, k5, k6, k7, k8;
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float hcmc;
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if( h < 49.1 ) {
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k4 = 133.87;
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k5 = -134.5;
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k6 = -.924;
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k7 = 1.727;
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k8 = 340.0;
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}
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else if( h < 110.1 ) {
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k4 = 11.78;
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k5 = -12.7;
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k6 = -.218;
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k7 = 2.12;
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k8 = 333.0;
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}
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else if( h < 269.6 ) {
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k4 = 13.87;
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k5 = 10.93;
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k6 = 0.14;
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k7 = 1.0;
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k8 = -83.0;
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}
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else {
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k4 = .14;
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k5 = 5.23;
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k6 = .17;
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k7 = 1.61;
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k8 = 233.0;
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}
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P = cos( VIPS_RAD( k7 * h + k8 ) );
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D = k4 + k5 * P * pow( VIPS_FABS( P ), k6 );
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g = C * C * C * C;
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f = sqrt( g / (g + 1900.0) );
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hcmc = h + D * f;
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return( hcmc );
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}
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static void
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vips_LCh2CMC_line( VipsColour *colour, VipsPel *out, VipsPel **in, int width )
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{
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float *p = (float *) in[0];
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float *q = (float *) out;
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int x;
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for( x = 0; x < width; x++ ) {
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float L = p[0];
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float C = p[1];
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float h = p[2];
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p += 3;
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q[0] = vips_col_L2Lcmc( L );
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q[1] = vips_col_C2Ccmc( C );
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q[2] = vips_col_Ch2hcmc( C, h );
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q += 3;
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}
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}
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static void
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vips_LCh2CMC_class_init( VipsLCh2CMCClass *class )
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{
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VipsObjectClass *object_class = (VipsObjectClass *) class;
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VipsColourClass *colour_class = VIPS_COLOUR_CLASS( class );
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object_class->nickname = "LCh2CMC";
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object_class->description = _( "transform LCh to CMC" );
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colour_class->process_line = vips_LCh2CMC_line;
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}
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static void
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vips_LCh2CMC_init( VipsLCh2CMC *LCh2CMC )
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{
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VipsColour *colour = VIPS_COLOUR( LCh2CMC );
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colour->interpretation = VIPS_INTERPRETATION_CMC;
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}
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/**
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* vips_LCh2CMC: (method)
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* @in: input image
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* @out: (out): output image
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* @...: %NULL-terminated list of optional named arguments
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*
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* Turn LCh to CMC.
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*
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* The CMC colourspace is described in "Uniform Colour Space Based on the
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* CMC(l:c) Colour-difference Formula", M R Luo and B Rigg, Journal of the
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* Society of Dyers and Colourists, vol 102, 1986. Distances in this
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* colourspace approximate, within 10% or so, differences in the CMC(l:c)
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* colour difference formula.
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*
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* This operation generates CMC(1:1). For CMC(2:1), halve Lucs and double
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* Cucs.
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*
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* See also: vips_CMC2LCh().
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*
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* Returns: 0 on success, -1 on error
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*/
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int
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vips_LCh2CMC( VipsImage *in, VipsImage **out, ... )
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{
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va_list ap;
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int result;
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va_start( ap, out );
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result = vips_call_split( "LCh2CMC", ap, in, out );
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va_end( ap );
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return( result );
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}
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