From cb7991be0618d0a7d69eb625e47f7c02ff66ba13 Mon Sep 17 00:00:00 2001
From: Nicolas Robidoux <nicolas.robidoux@gmail.com>
Date: Wed, 18 Mar 2009 03:42:19 +0000
Subject: [PATCH] more legible/a bit faster

---
 libsrc/resample/nohalo1.cpp | 47 ++++++++++++++++++++-----------------
 1 file changed, 26 insertions(+), 21 deletions(-)

diff --git a/libsrc/resample/nohalo1.cpp b/libsrc/resample/nohalo1.cpp
index ee21101a..94c32850 100644
--- a/libsrc/resample/nohalo1.cpp
+++ b/libsrc/resample/nohalo1.cpp
@@ -1,7 +1,7 @@
 /* nohalo level 1 interpolator
  *
  * Hacked for vips by J. Cupitt, 20/1/09
- * Tweaks by N. Robidoux and J. Cupitt 3/09
+ * Tweaks by N. Robidoux and J. Cupitt 4-17/3/09
  *
  * 16/3/09
  * 	- rename as nohalo1
@@ -467,44 +467,49 @@ nohalo1( const double           uno_two,
   { \
     T* restrict out = (T *) pout; \
     \
-    const int relative_y_is_down = ( relative_y >= 0. ); \
     const int relative_x_is_rite = ( relative_x >= 0. ); \
+    const int relative_y_is_down = ( relative_y >= 0. ); \
     \
-    const int sign_of_relative_y = 2 * relative_y_is_down - 1; \
     const int sign_of_relative_x = 2 * relative_x_is_rite - 1; \
+    const int sign_of_relative_y = 2 * relative_y_is_down - 1; \
     \
     const int corner_reflection_shift = \
-      relative_y_is_down * lskip + relative_x_is_rite * bands; \
+      relative_x_is_rite * bands + relative_y_is_down * lskip; \
     \
-    const int shift_1_row    = sign_of_relative_y * lskip; \
-    const int shift_1_pixel  = sign_of_relative_x * bands; \
+    const int shift_back_1_pixel  = sign_of_relative_x * bands; \
+    const int shift_back_1_row    = sign_of_relative_y * lskip; \
     \
     const T* restrict in = ( (T *) pin ) + corner_reflection_shift; \
     \
-    const int uno_two_shift = shift_1_row; \
-    const int uno_thr_shift = shift_1_row - shift_1_pixel; \
-    \
-    const int dos_one_shift = shift_1_pixel; \
-    const int dos_two_shift = 0; \
-    const int dos_thr_shift = -shift_1_pixel; \
+    const int shift_forw_1_pixel = -shift_back_1_pixel; \
+    const int shift_forw_1_row   = -shift_back_1_row; \
     \
     const double w = ( 2 * sign_of_relative_x ) * relative_x; \
     const double z = ( 2 * sign_of_relative_y ) * relative_y; \
     \
-    const int dos_fou_shift = 2 * dos_thr_shift; \
+    const int shift_forw_2_pixel = 2 * shift_forw_1_pixel; \
+    const int shift_forw_2_row   = 2 * shift_forw_1_row; \
+    \
+    const int uno_two_shift =                      shift_back_1_row; \
+    const int uno_thr_shift = shift_forw_1_pixel + shift_back_1_row; \
     \
     const double x = 1. - w; \
-    \
-    const int tre_one_shift = dos_one_shift - shift_1_row; \
-    const int tre_two_shift = -shift_1_row; \
-    const int tre_thr_shift = dos_thr_shift - shift_1_row; \
-    const int tre_fou_shift = dos_fou_shift - shift_1_row; \
-    \
     const double w_times_z = w * z; \
+    \
+    const int dos_one_shift = shift_back_1_pixel; \
+    const int dos_two_shift = 0; \
+    const int dos_thr_shift = shift_forw_1_pixel; \
+    const int dos_fou_shift = shift_forw_2_pixel; \
+    \
+    const int tre_one_shift = shift_back_1_pixel + shift_forw_1_row; \
+    const int tre_two_shift =                      shift_forw_1_row; \
+    const int tre_thr_shift = shift_forw_1_pixel + shift_forw_1_row; \
+    const int tre_fou_shift = shift_forw_2_pixel + shift_forw_1_row; \
+    \
     const double x_times_z = x * z; \
     \
-    const int qua_two_shift = tre_two_shift - shift_1_row; \
-    const int qua_thr_shift = tre_thr_shift - shift_1_row; \
+    const int qua_two_shift =                      shift_forw_2_row; \
+    const int qua_thr_shift = shift_forw_1_pixel + shift_forw_2_row; \
     \
     const double w_times_y_over_4 = .25  * ( w - w_times_z ); \
     const double x_times_z_over_4 = .25  * x_times_z; \