121 lines
2.4 KiB
C
121 lines
2.4 KiB
C
/* $XConsortium: hsbramp.c /main/3 1995/11/02 16:07:23 rswiston $ */
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/*
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*/
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/* *
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* (c) Copyright 1993, 1994 Hewlett-Packard Company *
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* (c) Copyright 1993, 1994 International Business Machines Corp. *
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* (c) Copyright 1993, 1994 Sun Microsystems, Inc. *
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* (c) Copyright 1993, 1994 Novell, Inc. *
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*/
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/*-
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* hsbramp.c - Create an HSB ramp.
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*
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* Copyright (c) 1991 by Patrick J. Naughton.
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*
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* See dtscreen.c for copying information.
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*
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* Revision History:
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* 29-Jul-90: renamed hsbramp.c from HSBmap.c
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* minor optimizations.
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* 01-Sep-88: Written.
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*/
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#include <sys/types.h>
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#include <math.h>
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void
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hsb2rgb(H, S, B, r, g, b)
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double H,
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S,
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B;
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u_char *r,
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*g,
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*b;
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{
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int i;
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double f;
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double bb;
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u_char p;
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u_char q;
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u_char t;
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H -= floor(H); /* remove anything over 1 */
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H *= 6.0;
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i = floor(H); /* 0..5 */
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f = H - (float) i; /* f = fractional part of H */
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bb = 255.0 * B;
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p = (u_char) (bb * (1.0 - S));
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q = (u_char) (bb * (1.0 - (S * f)));
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t = (u_char) (bb * (1.0 - (S * (1.0 - f))));
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switch (i) {
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case 0:
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*r = (u_char) bb;
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*g = t;
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*b = p;
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break;
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case 1:
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*r = q;
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*g = (u_char) bb;
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*b = p;
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break;
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case 2:
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*r = p;
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*g = (u_char) bb;
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*b = t;
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break;
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case 3:
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*r = p;
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*g = q;
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*b = (u_char) bb;
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break;
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case 4:
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*r = t;
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*g = p;
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*b = (u_char) bb;
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break;
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case 5:
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*r = (u_char) bb;
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*g = p;
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*b = q;
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break;
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}
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}
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/*
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* Input is two points in HSB color space and a count
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* of how many discreet rgb space values the caller wants.
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*
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* Output is that many rgb triples which describe a linear
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* interpolate ramp between the two input colors.
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*/
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void
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hsbramp(h1, s1, b1, h2, s2, b2, count, red, green, blue)
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double h1,
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s1,
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b1,
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h2,
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s2,
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b2;
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int count;
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u_char *red,
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*green,
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*blue;
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{
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double dh;
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double ds;
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double db;
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dh = (h2 - h1) / count;
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ds = (s2 - s1) / count;
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db = (b2 - b1) / count;
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while (count--) {
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hsb2rgb(h1, s1, b1, red++, green++, blue++);
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h1 += dh;
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s1 += ds;
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b1 += db;
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}
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}
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