[test] Update extend-pad.

extend-pad was not a clear demonstration of the EXTEND_PAD mode, so revamp
it to show the filter extending a 4 pixel surface to cover the entire
output. However, this hides a discrepancy with the vector surfaces that we
cannot prevent the external renders from applying an interpolation to the
border pixels, so we copy the original test to extend-pad-border to check
the desired behaviour on boundary pixels.

1 files changed, 0 insertions, 0 deletions

diff --git a/test/extend-pad-similar.ref.png b/test/extend-pad-similar.ref.png
new file mode 100644
index 00000000..82da7b65
--- /dev/null
+++ b/test/extend-pad-similar.ref.png