Multitouch gestures

project/jni/sdl-1.2/src/video/android/atan2i.h

@@ -0,0 +1,33 @@
+#ifndef __ATAN2I_H__
+#define __ATAN2I_H__
+#include <math.h>
+
+// Fast arctan2, returns angle in radians as integer, with fractional part in lower 16 bits
+// Stolen from http://www.dspguru.com/dsp/tricks/fixed-point-atan2-with-self-normalization , precision is said to be 0.07 rads
+
+#ifndef M_PI
+#define M_PI 3.14159265358979323846
+#endif
+enum { atan2i_coeff_1 = ((int)(M_PI*65536.0/4)), atan2i_coeff_2 = (3*atan2i_coeff_1), atan2i_PI = (int)(M_PI * 65536.0) };
+
+static inline int atan2i(int y, int x)
+{
+   int angle;
+   int abs_y = abs(y);
+   if( abs_y == 0 )
+      abs_y = 1;
+   if (x>=0)
+   {
+      angle = atan2i_coeff_1 - atan2i_coeff_1 * (x - abs_y) / (x + abs_y);
+   }
+   else
+   {
+      angle = atan2i_coeff_2 - atan2i_coeff_1 * (x + abs_y) / (abs_y - x);
+   }
+   if (y < 0)
+      return(-angle);     // negate if in quad III or IV
+   else
+      return(angle);
+};
+
+#endif