graphics.c: Fix windowing function to be more exact and prevent asymm…

…etric results
imazen · Sep 25, 2020 · fee4501 · fee4501
1 parent cf3f3f4
commit fee4501
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Showing 4 changed files with 135 additions and 133 deletions.
diff --git a/c_components/lib/graphics.c b/c_components/lib/graphics.c
@@ -407,8 +407,8 @@ flow_interpolation_line_contributions_create(flow_c * context, const uint32_t ou
     for (u = 0; u < output_line_size; u++) {
         const double center_src_pixel = ((double)u + 0.5) / scale_factor - 0.5;
 
-        const int left_edge = (int)floor(center_src_pixel) - ((allocated_window_size - 1) / 2);
-        const int right_edge = left_edge + allocated_window_size - 1;
+        const int left_edge =  (int)ceil(center_src_pixel - details->window/downscale_factor -0.0001);
+        const int right_edge = (int)floor(center_src_pixel + details->window/downscale_factor +0.0001);
 
         const uint32_t left_src_pixel = (uint32_t)int_max(0, left_edge);
         const uint32_t right_src_pixel = (uint32_t)int_min(right_edge, (int)input_line_size - 1);

diff --git a/c_components/tests/test_weighting.cpp b/c_components/tests/test_weighting.cpp
@@ -102,10 +102,12 @@ TEST_CASE("Verify weights are symmetric and bounded", "[fastscaling]")
     // filter, 2, from, 200, to, 300, weights, src, 0, (0.00001, 0.00200, 1.2200), 1, ...
     int32_t filter_id = 1;
     int32_t scalings[] = { /*downscale to 1px*/ 1, 1, 2, 1, 3, 1, 4, 1,  5, 1, 6, 1, 7, 1, 17, 1,
-                           /*upscale from 2px*/ 2, 3, 2, 4, 2, 5, 2, 17,
-                           /*other*/ 11,           7, 7, 3, 8, 4 };
+        /*upscale from 2px*/ 2, 3, 2, 4, 2, 5, 2, 17,
+        /*other*/ 11,           7, 7, 3,
+        /* IDCT kernel sizes */ 8, 8, 8, 7, 8, 6, 8, 5, 8, 4, 8, 3, 8, 2, 8, 1 };
 
-    flow_interpolation_filter first_filter = flow_interpolation_filter_NCubicSharp;
+    flow_interpolation_filter first_filter = flow_interpolation_filter_RobidouxFast;
+    //flow_interpolation_filter first_filter = flow_interpolation_filter_NCubicSharp;
     flow_interpolation_filter last_filter = flow_interpolation_filter_NCubicSharp;
     uint32_t scaling_ix;
     for (filter_id = (int32_t)first_filter; filter_id <= (int32_t)last_filter; filter_id++) {