[Pixman] [PATCH 12/15] pixman-filter: Turn off subsampling when not necessary

[spitzak at gmail.com]

From: Bill Spitzak <spitzak at gmail.com>

If sample is IMPULSE and reconstruct is BOX or IMPULSE the sub-pixel
position of the sample is not relevant, so only one subsample is needed.
---
 pixman/pixman-filter.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/pixman/pixman-filter.c b/pixman/pixman-filter.c
index 64981cd..7e10108 100644
--- a/pixman/pixman-filter.c
+++ b/pixman/pixman-filter.c
@@ -230,6 +230,8 @@ filter_width (pixman_kernel_t reconstruct,
 	      pixman_kernel_t sample,
 	      double scale)
 {
+    if (reconstruct == PIXMAN_KERNEL_BOX && sample == PIXMAN_KERNEL_IMPULSE)
+	return 0;
     return ceil (scale * filters[sample].width + filters[reconstruct].width);
 }
 
@@ -323,13 +325,13 @@ pixman_filter_create_separable_convolution (int             *n_values,
     int subsample_x, subsample_y;
     int width, height;
 
-    subsample_x = (1 << subsample_bits_x);
-    subsample_y = (1 << subsample_bits_y);
-
     width = filter_width (reconstruct_x, sample_x, sx);
-    if (width < 1) width = 1;
+    if (width < 1) { width = 1; subsample_bits_x = 0; }
     height = filter_width (reconstruct_y, sample_y, sy);
-    if (height < 1) height = 1;
+    if (height < 1) { height = 1; subsample_bits_y = 0; }
+
+    subsample_x = (1 << subsample_bits_x);
+    subsample_y = (1 << subsample_bits_y);
 
     *n_values = 4 + width * subsample_x + height * subsample_y;
 
-- 
1.9.1