use atan2 and hypot more

might be a little quicker

TODO

@@ -4,7 +4,7 @@
 
   try to_polar, set LBB, zoom in and scroll around a bit
 
-- speed up rect with atan2?
+
 
 - vips_resize() should not use the anti-alias filter if vips_shrink() has
   not been called, ie. for shrinks < 2 or so

configure.ac

@@ -340,6 +340,7 @@ AC_FUNC_VPRINTF
 AC_CHECK_FUNCS([getcwd gettimeofday getwd memset munmap putenv realpath strcasecmp strchr strcspn strdup strerror strrchr strspn vsnprintf realpath mkstemp mktemp random rand sysconf atexit])
 AC_CHECK_LIB(m,cbrt,[AC_DEFINE(HAVE_CBRT,1,[have cbrt() in libm.])])
 AC_CHECK_LIB(m,hypot,[AC_DEFINE(HAVE_HYPOT,1,[have hypot() in libm.])])
+AC_CHECK_LIB(m,atan2,[AC_DEFINE(HAVE_ATAN2,1,[have atan2() in libm.])])
 
 # have to have these
 # need glib 2.6 for GOption

libvips/arithmetic/complex.c

@@ -131,13 +131,41 @@ G_DEFINE_TYPE( VipsComplex, vips_complex, VIPS_TYPE_UNARY );
 		g_assert( 0 ); \
 	} 
 
+static double
+vips_complex_hypot( double a, double b )
+{
+	double d;
+
+#ifdef HAVE_HYPOT
+	d = hypot( a, b ); 
+#else
+	d = sqrt( a * a + b * b );
+#endif
+
+	return( d ); 
+}
+
+static double
+vips_complex_atan2( double a, double b )
+{
+	double h;
+
+#ifdef HAVE_ATAN2
+	h = VIPS_DEG( atan2( b, a ) );
+#else
+	h = vips_col_ab2h( a, b ); 
+#endif 
+
+	return( h ); 
+}
+
 #define POLAR( Q, X, Y ) { \
 	double re = (X); \
 	double im = (Y); \
 	double am, ph; \
 	\
-	am = sqrt( re * re + im * im ); \
+	am = vips_complex_hypot( re, im ); \
-	ph = vips_col_ab2h( re, im ); \
+	ph = vips_complex_atan2( re, im ); \
 	\
 	Q[0] = am; \
 	Q[1] = ph; \

libvips/colour/Lab2LCh.c

@@ -63,6 +63,9 @@ vips_col_ab2h( double a, double b )
 {
 	double h;
 
+#ifdef HAVE_ATAN2
+	h = VIPS_DEG( atan2( b, a ) );
+#else
 	/* We have to get the right quadrant!
 	 */
 	if( a == 0 ) {
@@ -84,6 +87,7 @@ vips_col_ab2h( double a, double b )
 		else
 			h = VIPS_DEG( t + VIPS_PI );
 	}
+#endif
 
 	return( h );
 }
@@ -91,8 +95,17 @@ vips_col_ab2h( double a, double b )
 void
 vips_col_ab2Ch( float a, float b, float *C, float *h )
 {
+#ifdef HAVE_ATAN2
+	*h = VIPS_DEG( atan2( b, a ) );
+#else
 	*h = vips_col_ab2h( a, b ); 
+#endif 
+
+#ifdef HAVE_HYPOT
+	*C = hypot( a, b ); 
+#else
 	*C = sqrt( a * a + b * b );
+#endif
 }
 
 static void