[gegl] buffer: speed up NEAREST gegl_buffer_sample

[Øyvind Kolås <ok src gnome org>]

commit c8eb73eb761ee3b7a393fbb785117db0c96f98f8
Author: Øyvind Kolås <pippin gimp org>
Date:   Tue May 15 11:36:53 2018 +0200

    buffer: speed up NEAREST gegl_buffer_sample
    
    For the nearest neighbor case, use gegl_buffer_get with a 1x1 rectangle instead
    of a temporary sampler.

 gegl/buffer/gegl-sampler.c |   47 +++++++++++++++++++++++++++++++++----------
 1 files changed, 36 insertions(+), 11 deletions(-)
---
diff --git a/gegl/buffer/gegl-sampler.c b/gegl/buffer/gegl-sampler.c
index a9a4246..b63dbec 100644
--- a/gegl/buffer/gegl-sampler.c
+++ b/gegl/buffer/gegl-sampler.c
@@ -414,19 +414,29 @@ gegl_sampler_gtype_from_enum (GeglSamplerType sampler_type)
     }
 }
 
-void
-gegl_buffer_sample_at_level (GeglBuffer       *buffer,
-                             gdouble           x,
-                             gdouble           y,
-                             GeglMatrix2      *scale,
-                             gpointer          dest,
-                             const Babl       *format,
-                             gint              level,
-                             GeglSamplerType   sampler_type,
-                             GeglAbyssPolicy   repeat_mode)
+static inline void
+_gegl_buffer_sample_at_level (GeglBuffer       *buffer,
+                              gdouble           x,
+                              gdouble           y,
+                              GeglMatrix2      *scale,
+                              gpointer          dest,
+                              const Babl       *format,
+                              gint              level,
+                              GeglSamplerType   sampler_type,
+                              GeglAbyssPolicy   repeat_mode)
 {
   GeglSampler *sampler;
 
+  if (sampler_type == GEGL_SAMPLER_NEAREST &&
+      level == 0)
+    {
+      GeglRectangle rect = {x, y, 1, 1};
+      gegl_buffer_get (buffer, &rect, 1.0,
+                       format, dest, GEGL_AUTO_ROWSTRIDE,
+                       repeat_mode);
+      return;
+    }
+
   if (!format)
     format = buffer->soft_format;
 
@@ -438,6 +448,21 @@ gegl_buffer_sample_at_level (GeglBuffer       *buffer,
   g_object_unref (sampler);
 }
 
+void
+gegl_buffer_sample_at_level (GeglBuffer       *buffer,
+                             gdouble           x,
+                             gdouble           y,
+                             GeglMatrix2      *scale,
+                             gpointer          dest,
+                             const Babl       *format,
+                             gint              level,
+                             GeglSamplerType   sampler_type,
+                             GeglAbyssPolicy   repeat_mode)
+{
+  _gegl_buffer_sample_at_level (buffer, x, y, scale, dest,
+                                format, level, sampler_type, repeat_mode);
+}
+
 
 void
 gegl_buffer_sample (GeglBuffer       *buffer,
@@ -449,7 +474,7 @@ gegl_buffer_sample (GeglBuffer       *buffer,
                     GeglSamplerType   sampler_type,
                     GeglAbyssPolicy   repeat_mode)
 {
-  gegl_buffer_sample_at_level (buffer, x, y, scale, dest, format, 0, sampler_type, repeat_mode);
+  _gegl_buffer_sample_at_level (buffer, x, y, scale, dest, format, 0, sampler_type, repeat_mode);
 }
 
 void