ftp://ftp.ntnu.no/old/pub/X11/R5contrib/xscreensaver-1.17.tar.gz

[xscreensaver] / utils / hsv.c

diff --git a/utils/hsv.c b/utils/hsv.c
new file mode 100644 (file)
index 0000000..bf508f3
--- /dev/null
+++ b/utils/hsv.c
@@ -0,0 +1,110 @@
+/* xscreensaver, Copyright (c) 1992 Jamie Zawinski <jwz@lucid.com>
+ *
+ * Permission to use, copy, modify, distribute, and sell this software and its
+ * documentation for any purpose is hereby granted without fee, provided that
+ * the above copyright notice appear in all copies and that both that
+ * copyright notice and this permission notice appear in supporting
+ * documentation.  No representations are made about the suitability of this
+ * software for any purpose.  It is provided "as is" without express or 
+ * implied warranty.
+ */
+
+/* This file contains some utility routines for randomly picking the colors
+   to hack the screen with.
+ */
+
+#include <X11/Xlib.h>
+
+void
+hsv_to_rgb (h,s,v, r,g,b)
+     int h;                    /* 0 - 360   */
+     double s, v;              /* 0.0 - 1.0 */
+     unsigned short *r, *g, *b;        /* 0 - 65535 */
+{
+  double H, S, V, R, G, B;
+  double p1, p2, p3;
+  double f;
+  int i;
+  S = s; V = v;
+  H = (h % 360) / 60.0;
+  i = H;
+  f = H - i;
+  p1 = V * (1 - S);
+  p2 = V * (1 - (S * f));
+  p3 = V * (1 - (S * (1 - f)));
+  if     (i == 0) { R = V;  G = p3; B = p1; }
+  else if (i == 1) { R = p2; G = V;  B = p1; }
+  else if (i == 2) { R = p1; G = V;  B = p3; }
+  else if (i == 3) { R = p1; G = p2; B = V;  }
+  else if (i == 4) { R = p3; G = p1; B = V;  }
+  else            { R = V;  G = p1; B = p2; }
+  *r = R * 65535;
+  *g = G * 65535;
+  *b = B * 65535;
+}
+
+void
+rgb_to_hsv (r,g,b, h,s,v)
+     unsigned short r, g, b;   /* 0 - 65535 */
+     int *h;                   /* 0 - 360   */
+     double *s, *v;            /* 0.0 - 1.0 */
+{
+  double R, G, B, H, S, V;
+  double cmax, cmin;
+  double cmm;
+  int imax;
+  R = ((double) r) / 65535.0;
+  G = ((double) g) / 65535.0;
+  B = ((double) b) / 65535.0;
+  cmax = R; cmin = G; imax = 1;
+  if  ( cmax < G ) { cmax = G; cmin = R; imax = 2; }
+  if  ( cmax < B ) { cmax = B; imax = 3; }
+  if  ( cmin > B ) { cmin = B; }
+  cmm = cmax - cmin;
+  V = cmax;
+  if (cmm == 0)
+    S = H = 0;
+  else
+    {
+      S = cmm / cmax;
+      if      (imax == 1) H =       (G - B) / cmm;
+      else if (imax == 2) H = 2.0 + (B - R) / cmm;
+      else if (imax == 3) H = 4.0 + (R - G) / cmm;
+      if (H < 0) H += 6.0;
+    }
+  *h = (H * 60.0);
+  *s = S;
+  *v = V;
+}
+
+
+void
+make_color_ramp (h1, s1, v1, h2, s2, v2,
+                pixels, npixels)
+     int h1, h2;                       /* 0 - 360   */
+     double s1, s2, v1, v2;            /* 0.0 - 1.0 */
+     XColor *pixels;
+     int npixels;
+{
+  int dh = (h2 - h1) / npixels;
+  double ds = (s2 - s1) / npixels;
+  double dv = (v2 - v1) / npixels;
+  int i;
+  for (i = 0; i < npixels; i++)
+    hsv_to_rgb ((h1 += dh), (s1 += ds), (v1 += dv),
+               &pixels [i].red, &pixels [i].green, &pixels [i].blue);
+}
+
+
+void
+cycle_hue (color, degrees)
+     XColor *color;
+     int degrees;
+{
+  int h;
+  double s, v;
+  rgb_to_hsv (color->red, color->green, color->blue,
+             &h, &s, &v);
+  h = (h + degrees) % 360;
+  hsv_to_rgb (h, s, v, &color->red, &color->green, &color->blue);
+}