326 lines
8.2 KiB
C
326 lines
8.2 KiB
C
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/*
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* CMWrgbhsv.c --
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*
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* Procedures to translate between RGB color space and HSV color space.
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* Courtesy of Ken Fishkin.
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*
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* *********************************************************************
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* * Copyright (C) 1985, 1990 Regents of the University of California. *
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* * Permission to use, copy, modify, and distribute this *
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* * software and its documentation for any purpose and without *
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* * fee is hereby granted, provided that the above copyright *
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* * notice appear in all copies. The University of California *
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* * makes no representations about the suitability of this *
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* * software for any purpose. It is provided "as is" without *
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* * express or implied warranty. Export of this software outside *
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* * of the United States of America may require an export license. *
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* *********************************************************************
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*/
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#ifndef lint
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static char rcsid[] __attribute__ ((unused)) = "$Header: /usr/cvsroot/magic-8.0/cmwind/CMWrgbhsv.c,v 1.1.1.1 2008/02/03 20:43:50 tim Exp $";
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#endif /* not lint */
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#include <stdio.h>
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#include <math.h>
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#include "utils/magic.h"
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/* max of three numbers */
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#define MAX3(a,b,c) (a > b ? (a > c ? a : c) : ( b > c ?b : c))
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/* and min */
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#define MIN3(a,b,c) (a < b ? (a < c ? a : c) : ( b < c ?b : c))
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/*
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|-----------------------------------------------------------------------|
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| procedure : RGBxHSV |
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| description : given r,g,b, each on [0,1], return hue, sat- |
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| : uration, and value, each on [0,1]. |
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| : returns true <==> hue is defined. |
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| source : Smith, Alvy Ray. "Color Tutorial Notes". |
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| : Technical Memo 37, LucasFilm. |
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| : hue calc changed a tad, according to Foley |
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| : and Van Dam. |
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|-----------------------------------------------------------------------|
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*/
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bool
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RGBxHSV( r, g, b, h, s, v)
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double r, g, b;
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double *h, *s, *v;
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{
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double max, delta;
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double mr,mg,mb;
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*v = max = MAX3(r,g,b);
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if ( (max == 0) || ( (delta = max - MIN3(r,g,b) ) == 0) ) {
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/* achromatic */
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*s = 0;
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*h = 0;
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return(FALSE);
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};
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*s = delta/ max;
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mr = (max - r)/delta;
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mg = (max - g)/delta;
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mb = (max - b)/delta;
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if (r == max)
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*h = mb - mg;
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else if ( g == max)
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*h = 2.0 + mr - mb;
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else if ( b == max)
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*h = 4.0 + mg - mr;
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*h /= 6;
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if (*h < 0.0)
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*h += 1.0;
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return(TRUE);
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}
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/*
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|-----------------------------------------------------------------------|
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| procedure : HSVxRGB |
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| description : given HSV on [0,1], returns equivalent |
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| : RGB on [0,1]. |
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| source : Smith, Alvy Ray. "Color Tutorial Notes". |
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| : Technical Memo 37, LucasFilm. |
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|-----------------------------------------------------------------------|
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*/
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#define SETRGB(rr,gg,bb) *r=rr;*g=gg;*b=bb
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void
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HSVxRGB( h,s,v,r,g,b)
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double h,s,v;
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double *r,*g,*b;
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{
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double f,m,n,k;
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int i;
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double vs,vsf;
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h *= 6;
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i = h; /* integer part of hue */
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f = h - i; /* fractional part */
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vs = v*s;
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vsf = vs*f;
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m = v - vs;
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n = v - vsf;
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k = v - vs + vsf;
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switch(i % 6) {
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case 0 : SETRGB( v,k,m); break;
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case 1 : SETRGB( n,v,m); break;
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case 2 : SETRGB( m,v,k); break;
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case 3 : SETRGB( m,n,v); break;
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case 4 : SETRGB( k,m,v); break;
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case 5 : SETRGB( v,m,n); break;
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}
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}
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/*
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|-----------------------------------------------------------------------|
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| procedure : RGBxHSL |
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| description : converts from RGB to HSL coordinates. |
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| source : '79 graphics core. |
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|-----------------------------------------------------------------------|
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*/
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bool
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RGBxHSL( r, g, b, h, s, l )
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double r, g, b;
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double *h, *s, *l;
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{
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double min, max;
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double delta, mr, mg, mb;
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min = MIN3( r,g,b);
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max = MAX3( r,g,b);
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/* Lightness calculation */
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/* source - 79 graphics core */
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*l = 0.5 * (max + min);
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if ( (delta = max - min) == 0) {
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/* achromatic */
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*s = 0.0;
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*h = 0.0;
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return FALSE;
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}
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/* Saturation calculation */
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/* HSL is a double cone */
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if (*l < 0.5)
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*s = (delta)/(max+min);
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else
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*s = (delta)/(2.0-(max+min));
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/* hue calculation */
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mr = (max - r)/delta;
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mg = (max - g)/delta;
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mb = (max - b)/delta;
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if (r == max)
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*h = mb - mg;
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else if ( g == max)
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*h = 2.0 + mr - mb;
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else if ( b == max)
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*h = 4.0 + mg - mr;
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*h /= 6;
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if (*h < 0.0)
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*h += 1.0;
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return(TRUE);
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}
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/*
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|-----------------------------------------------------------------------|
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| procedure : HSLxRGB |
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| description : converts from HSL, each on [0,1], to RGB, |
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| : each on [0,1]. |
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| note : the idea is to use s,l to get HSV s,v, and |
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| : then use HSVxRGB - this is faster than the |
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| : '79 core algorithm. |
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|-----------------------------------------------------------------------|
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*/
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void
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HSLxRGB( h, s, l, r, g, b )
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double h, s, l;
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double *r, *g, *b;
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{
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double min;
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double v;
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double f,n,k;
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int i;
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double vsf;
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if ( l <= 0.5)
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v = l * (1.0 + s);
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else
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v = l + s - l*s;
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min = 2*l - v;
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if ( (s == 0.0) || ( l == 0.0) || ( l == 1.0 ) ) {
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SETRGB(l,l,l);
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return;
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}
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/* now just use hsvxrgb */
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s = ( v - min) / v;
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h *= 6;
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i = h; /* integer part of hue */
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f = h - i; /* fractional part */
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vsf = v*s*f;
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n = v - vsf;
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k = min + vsf;
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switch(i % 6) {
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case 0 : SETRGB( v,k,min); break;
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case 1 : SETRGB( n,v,min); break;
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case 2 : SETRGB( min,v,k); break;
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case 3 : SETRGB( min,n,v); break;
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case 4 : SETRGB( k,min,v); break;
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case 5 : SETRGB( v,min,n); break;
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}
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}
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/*
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|-----------------------------------------------------------------------|
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| procedure : Correct_chromaticity |
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| description : given the white point at location (wx,wy), |
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| : and an existing point (x,y), such that |
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| : x + y > 1, intersect a line through the |
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| : white point and the exisiting point with the |
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| : line x+y = 1. side-affects new point. |
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|-----------------------------------------------------------------------|
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*/
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void
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Correct_chromaticity(x, y, wx, wy)
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double *x,*y;
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double wx,wy;
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{
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double oldx,oldy;
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double slope;
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double b;
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oldx = *x; oldy = *y;
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slope = ( oldy - wy ) / ( oldx - wx);
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/* find b by eval'ing at white point */
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b = wy - slope*wx;
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*x = ( 1.0 - b ) / ( 1.0 + slope);
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*y = 1.0 - *x;
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}
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/*
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|-----------------------------------------------------------------------|
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| procedure : xyz_to_mrgb |
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| description : converts xyz to monitor rgb. |
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| : only really correct for mitsubishi mon. |
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|-----------------------------------------------------------------------|
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*/
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void
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xyz_to_mrgb(x, y, z, mr, mg, mb)
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double x, y, z;
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double *mr, *mg, *mb;
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{
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*mr = 2.4513*x - 1.2249*y - 0.3237*z;
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*mg = -1.4746*x + 2.5052*y + 0.0596*z;
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*mb = 0.0212*x - 0.2550*y + 1.1487*z;
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}
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/*
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|-----------------------------------------------------------------------|
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| procedure : Make_mRGB_Nice |
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| description : make mRGB values lie in 0..1, correcting for |
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| : luminance overflow, chrominance irreproduc- |
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| : ibility. |
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| assumptions : at most one of mR,mG,mB < 0 |
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|-----------------------------------------------------------------------|
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*/
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void
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Make_mRGB_Nice(mR,mG,mB)
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double *mR,*mG,*mB;
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{
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double min,max;
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double mr, mg, mb;
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double mY;
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double white_mr,white_mg,white_mb;
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max = *mR;
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if ( max < *mG) max = *mG;
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if ( max < *mB) max = *mB;
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if ( max > 1.0) { /* luminance overflow, maintain chromaticity */
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*mR /= max;
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*mG /= max;
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*mB /= max;
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}
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min = *mR;
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if ( min > *mG) min = *mG;
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if ( min > *mB) min = *mB;
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if ( min >= 0.0 )
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return;
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/* correct in mrgb space */
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mY = *mR + *mG + *mB;
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mr = *mR/mY; mg = *mG / mY; mb = *mB / mY;
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/* correct based on which component is < 0 */
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/* find monitor white point */
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xyz_to_mrgb(1.0/3.0,1.0/3.0,1.0/3.0,&white_mr,&white_mg,&white_mb);
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if ( mr < 0 ) {
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mr = 0.0;
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Correct_chromaticity( &mg, &mb, white_mg,white_mb);
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} else if ( mg < 0 ) {
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mg = 0.0;
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Correct_chromaticity( &mr, &mb, white_mr,white_mb);
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} else if ( mb < 0 ) {
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mb = 0.0;
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Correct_chromaticity( &mr, &mg, white_mr,white_mg);
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}
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*mR = mr*mY;
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*mG = mg*mY;
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*mB = mb*mY;
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}
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