PS/PDF: Set image Interpolation flag

If the filter mode is anything other than DEFAILT, FAST or NEAREST set the
Interpolate flag in the image dictionary so that a smoothing filter is
applied when rasterising the vector file.

As we have no control over the implementation of the Interpolate filter
(the PS/PDF specifications leave it undefined) we need to capture the
output of poppler/GS and update our reference images. (For a couple of
tests, the filtering is irrelevant so for those we set the filter to
NEAREST.)

Note that GhostScript's Interpolate filter does not work on rotated images
(and a variety of other transformations) so several of the PS reference
images have use nearest-neighbour sampling instead of a bilinear filter.

1 files changed, 4 insertions, 2 deletions

diff --git a/test/surface-pattern-scale-up.c b/test/surface-pattern-scale-up.c
index 3c097532e..33f62fc0a 100644
--- a/test/surface-pattern-scale-up.c
+++ b/test/surface-pattern-scale-up.c
@@ -24,6 +24,9 @@
  * Author: Behdad Esfahbod <behdad@behdad.org>
  */
 
+/* Exhibits nasty behaviour with GS due as their /Interpolate implementation
+ * does not function for rotated images. */
+
 #include <math.h>
 #include "cairo-test.h"
 #include <stdio.h>
@@ -34,8 +37,7 @@ static cairo_test_draw_function_t draw;
 
 static const cairo_test_t test = {
     "surface-pattern-scale-up",
-    "Test scaled-up transformed not-repeated surface patterns"
-    "\nFails xlib backend (with argb32) with inexplicable alpha in result",
+    "Test scaled-up transformed not-repeated surface patterns",
     SIZE, SIZE,
     draw
 };