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, 1 insertions, 0 deletions

diff --git a/test/create-from-png.c b/test/create-from-png.c
index 5ed3f6169..9e2ad7f83 100644
--- a/test/create-from-png.c
+++ b/test/create-from-png.c
@@ -72,6 +72,7 @@ draw (cairo_t *cr, int width, int height)
     free (filename);
 
     cairo_set_source_surface (cr, surface, 0, 0);
+    cairo_pattern_set_filter (cairo_get_source (cr), CAIRO_FILTER_NEAREST);
     cairo_paint (cr);
 
     cairo_surface_destroy (surface);