Made the point up/down mapping for pyramid_down<2> and pyramid_down<3> a little

bit more accurate.

dlib/image_transforms/image_pyramid.h

@@ -156,8 +156,7 @@ namespace dlib
                 const vector<T,2>& p
             ) const
             {
-                //do return (p - vector<T,2>(2,2))/2.0;
-                return p/2.0 - vector<double,2>(1,1);
+                return p/2.0 - vector<double,2>(1.25,0.75);
             }
 
             template <typename T>
@@ -165,7 +164,7 @@ namespace dlib
                 const vector<T,2>& p
             ) const
             {
-                return p*2 + vector<T,2>(2,2);
+                return (p + vector<T,2>(1.25,0.75))*2;
             }
 
         // -----------------------------
@@ -497,8 +496,7 @@ namespace dlib
             ) const
             {
                 const double ratio = 2.0/3.0;
-                //do return (p - vector<T,2>(1,1))*ratio;
-                return p*ratio - vector<double,2>(ratio,ratio);
+                return p*ratio - vector<double,2>(1,1);
             }
 
             template <typename T>
@@ -507,7 +505,7 @@ namespace dlib
             ) const
             {
                 const double ratio = 3.0/2.0;
-                return p*ratio + vector<T,2>(1,1);
+                return p*ratio + vector<T,2>(ratio,ratio);
             }
 
         // -----------------------------

dlib/test/pyramid_down.cpp

@@ -206,7 +206,7 @@ void test_pyramid_down_rgb2()
 template <typename pyramid_down_type>
 void test_pyramid_down_grayscale2()
 {
-    array2d<unsigned char> img, img3;
+    array2d<unsigned char> img;
     array2d<unsigned char> img2, img4;
 
 
@@ -225,7 +225,6 @@ void test_pyramid_down_grayscale2()
     pyramid_down_type pyr;
 
     pyr(img, img2);
-    pyr(img, img3);
 
 
     DLIB_TEST(((rect1.tl_corner() - pyr.rect_down(pyr.rect_up(rect1,2),2).tl_corner()).length()) < 1);
@@ -246,17 +245,13 @@ void test_pyramid_down_grayscale2()
     /*
     image_window my_window(img);
     image_window win2(img2);
-    image_window win3(img3);
     win2.add_overlay(image_window::overlay_rect(rect1, rgb_pixel(255,0,0)));
     win2.add_overlay(image_window::overlay_rect(rect2, rgb_pixel(255,0,0)));
     win2.add_overlay(image_window::overlay_rect(rect3, rgb_pixel(255,0,0)));
-    win3.add_overlay(image_window::overlay_rect(rect1, rgb_pixel(255,0,0)));
-    win3.add_overlay(image_window::overlay_rect(rect2, rgb_pixel(255,0,0)));
-    win3.add_overlay(image_window::overlay_rect(rect3, rgb_pixel(255,0,0)));
     */
 
 
-    DLIB_TEST(std::abs((int)mean(subm(matrix_cast<long>(mat(img2)),rect1)) - 255) < 3);
+    DLIB_TEST(std::abs((int)mean(subm(matrix_cast<long>(mat(img2)),rect1)) - 255) <= 3);
     DLIB_TEST(std::abs((int)mean(subm(matrix_cast<long>(mat(img2)),rect2)) - 170) < 3);
     DLIB_TEST(std::abs((int)mean(subm(matrix_cast<long>(mat(img2)),rect3)) - 100) < 3);
     assign_image(img4, img);