Initial import of the CDE 2.1.30 sources from the Open Group.

cde/programs/dtscreen/hsbramp.c

@@ -0,0 +1,120 @@
+/* $XConsortium: hsbramp.c /main/3 1995/11/02 16:07:23 rswiston $ */
+/*
+ */
+/*                                                                      *
+ * (c) Copyright 1993, 1994 Hewlett-Packard Company                     *
+ * (c) Copyright 1993, 1994 International Business Machines Corp.       *
+ * (c) Copyright 1993, 1994 Sun Microsystems, Inc.                      *
+ * (c) Copyright 1993, 1994 Novell, Inc.                                *
+ */
+/*-
+ * hsbramp.c - Create an HSB ramp.
+ *
+ * Copyright (c) 1991 by Patrick J. Naughton.
+ *
+ * See dtscreen.c for copying information.
+ *
+ * Revision History:
+ * 29-Jul-90: renamed hsbramp.c from HSBmap.c
+ *	      minor optimizations.
+ * 01-Sep-88: Written.
+ */
+
+#include <sys/types.h>
+#include <math.h>
+
+void
+hsb2rgb(H, S, B, r, g, b)
+    double      H,
+                S,
+                B;
+    u_char     *r,
+               *g,
+               *b;
+{
+    int         i;
+    double      f;
+    double      bb;
+    u_char      p;
+    u_char      q;
+    u_char      t;
+
+    H -= floor(H);		/* remove anything over 1 */
+    H *= 6.0;
+    i = floor(H);		/* 0..5 */
+    f = H - (float) i;		/* f = fractional part of H */
+    bb = 255.0 * B;
+    p = (u_char) (bb * (1.0 - S));
+    q = (u_char) (bb * (1.0 - (S * f)));
+    t = (u_char) (bb * (1.0 - (S * (1.0 - f))));
+    switch (i) {
+    case 0:
+	*r = (u_char) bb;
+	*g = t;
+	*b = p;
+	break;
+    case 1:
+	*r = q;
+	*g = (u_char) bb;
+	*b = p;
+	break;
+    case 2:
+	*r = p;
+	*g = (u_char) bb;
+	*b = t;
+	break;
+    case 3:
+	*r = p;
+	*g = q;
+	*b = (u_char) bb;
+	break;
+    case 4:
+	*r = t;
+	*g = p;
+	*b = (u_char) bb;
+	break;
+    case 5:
+	*r = (u_char) bb;
+	*g = p;
+	*b = q;
+	break;
+    }
+}
+
+
+/*
+ * Input is two points in HSB color space and a count
+ * of how many discreet rgb space values the caller wants.
+ *
+ * Output is that many rgb triples which describe a linear
+ * interpolate ramp between the two input colors.
+ */
+
+void
+hsbramp(h1, s1, b1, h2, s2, b2, count, red, green, blue)
+    double      h1,
+                s1,
+                b1,
+                h2,
+                s2,
+                b2;
+    int         count;
+
+    u_char     *red,
+               *green,
+               *blue;
+{
+    double      dh;
+    double      ds;
+    double      db;
+
+    dh = (h2 - h1) / count;
+    ds = (s2 - s1) / count;
+    db = (b2 - b1) / count;
+    while (count--) {
+	hsb2rgb(h1, s1, b1, red++, green++, blue++);
+	h1 += dh;
+	s1 += ds;
+	b1 += db;
+    }
+}