From 8811d7023e3297021882b0edcaa03866a7329ee7 Mon Sep 17 00:00:00 2001
From: Fabien Freling <public@ffreling.com>
Date: Thu, 3 Jul 2014 23:54:06 +0200
Subject: [PATCH] Factorize rotated point computation

---
 rotation.cpp | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/rotation.cpp b/rotation.cpp
index 26a3b9e..f854934 100644
--- a/rotation.cpp
+++ b/rotation.cpp
@@ -627,8 +627,6 @@ Image* rotate(Image const& src, double angle)
   src_delta_y.y = src_delta_y.y - src_origin.y;
   round_if_very_small(src_delta_y.x);
   round_if_very_small(src_delta_y.y);
-  // cout << "src delta x = " << src_delta_x << endl;
-  // cout << "src delta y = " << src_delta_y << endl;
 
 
   // // steps for first column in source image (y)
@@ -637,10 +635,10 @@ Image* rotate(Image const& src, double angle)
   int line_nb_steps = max(abs(tr.x - tl.x), abs(tr.y - tl.y));
 
   // steps for first column in rotated image (y)
-  DPoint rotated_step((bl.x - tl.x) / (float) origin_nb_steps, (bl.y - tl.y) / (float) origin_nb_steps);
+  DPoint const rotated_step((bl.x - tl.x) / (float) origin_nb_steps, (bl.y - tl.y) / (float) origin_nb_steps);
 
   // steps for line in rotated image (x)
-  DPoint bresenham((tr.x - tl.x) / (float) line_nb_steps, (tr.y - tl.y) / (float) line_nb_steps);
+  DPoint const bresenham((tr.x - tl.x) / (float) line_nb_steps, (tr.y - tl.y) / (float) line_nb_steps);
 
   unsigned int const src_limit = src.width * src.height * 3;
   unsigned int const rot_limit = rotated->width * rotated->height * 3;
@@ -649,12 +647,13 @@ Image* rotate(Image const& src, double angle)
   {
     // first column origin
     Point const rot_origin(tl.x + y_i * rotated_step.x, tl.y + y_i * rotated_step.y);
+    Point rot_point(rot_origin.x, rot_origin.y);
+    DPoint rot_delta(0.0, 0.0);
 
     Point previous = rot_origin;
 
     for (int x_i = 0; x_i <= (int) line_nb_steps; ++x_i)
     {
-      Point rot_point(rot_origin.x + x_i * bresenham.x, rot_origin.y + x_i * bresenham.y);
 
       Point const delta(rot_point.x - tl.x, rot_point.y - tl.y);
       DPoint src_rotated_point(src_tl.x + delta.x * src_delta_x.x + delta.y * src_delta_y.x,
@@ -677,6 +676,12 @@ Image* rotate(Image const& src, double angle)
       }
 
       previous = rot_point;
+
+      rot_delta.x += bresenham.x;
+      rot_point.x = rot_origin.x + (int) rot_delta.x;
+
+      rot_delta.y += bresenham.y;
+      rot_point.y = rot_origin.y + (int) rot_delta.y;
     }
   }