Improve bilinear image scaling below 50%

The original code can not scale well below 50%. To improve
filtering in a fast way, huge images are scaled by powers of
two before fine scaling using the original bilinear scale.

1 files changed, 6 insertions, 0 deletions

diff --git a/FL/Fl_Image.H b/FL/Fl_Image.H
index 8b8b433e8..6cf1e1267 100644
--- a/FL/Fl_Image.H
+++ b/FL/Fl_Image.H
@@ -354,6 +354,12 @@ private:
   fl_uintptr_t id_;
   fl_uintptr_t mask_;
   int cache_w_, cache_h_; // size of image when cached
+
+  Fl_RGB_Image *copy_scale_down_2h_() const;
+  Fl_RGB_Image *copy_scale_down_2v_() const;
+  Fl_RGB_Image *copy_bilinear_(int W, int H) const;
+  Fl_RGB_Image *copy_nearest_neighbor_(int W, int H) const;
+  Fl_RGB_Image *copy_optimize_(int W, int H) const;
 public:
 
   Fl_RGB_Image(const uchar *bits, int W, int H, int D=3, int LD=0);