[gegl] color-reduction: speed up quantize_value by truncating with cast instead of calling floorf

[Øyvind "pippin" Kolås <ok src gnome org>]

commit 148a8e4627f4d276acf72218655891e601ecd656
Author: Øyvind Kolås <pippin gimp org>
Date:   Fri Feb 26 16:34:32 2021 +0100

    color-reduction: speed up quantize_value by truncating with cast instead of calling floorf

 operations/common/dither.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/operations/common/dither.c b/operations/common/dither.c
index cc66e9d7e..65a1b17cd 100644
--- a/operations/common/dither.c
+++ b/operations/common/dither.c
@@ -73,7 +73,7 @@ quantize_value (guint value,
                 guint n_levels)
 {
   float recip = 65535.0 / n_levels;
-  return floorf (value / recip) * recip;
+  return (int)(value / recip) * recip;
 }
 
 static void