[cairo] [PATCH 1/2] test: Add an update-refs.sh script to update reference images

[Bryce Harrington]

There are cases where the rendered output of a test can vary from
backend to backend in ways which are visually acceptable.  This is why
we have reference images in the first place.  In these cases, changes to
the rendering logic can result in slight differences in the output that
is also within acceptable visual limits.

We see this in the pixman downscaling tests.  This script is introduced
as a way to more easily update the reference images after a renderer
change.

This script is intended to be expanded to handle updating of references
for other tests as we identify similar issues.  The intent is that this
script then serves as a way to document these exceptional cases.

Signed-off-by: Bryce Harrington <bryce at osg.samsung.com>
---
 test/update-refs.sh |   84 +++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 84 insertions(+)
 create mode 100755 test/update-refs.sh

diff --git a/test/update-refs.sh b/test/update-refs.sh
new file mode 100755
index 0000000..104eeb8
--- /dev/null
+++ b/test/update-refs.sh
@@ -0,0 +1,84 @@
+#!/bin/bash
+
+# This script can be used to update the reference images using certain
+# test results as a baseline.
+#
+# Our test suite expects nearly pixel-perfection, but in some cases we
+# give the renderer some flexibility and so these cases will show up as
+# test failures.  So, this script can be used to do a visual check and
+# if they "look" ok, to go ahead and update the reference image by
+# copying the test output.
+#
+# NOTE: When adding to this file, make sure to thoroughly document the
+# rationale when and why the existing reference images can be updated
+# from regular test output, such that people other than you can
+# intelligently keep the test reference images updated.
+
+if [ ! -d output ] || [ ! -d reference ]; then
+    echo "This script must be run in cairo's test directory after the full testsuite has been run."
+    exit
+fi
+
+PDIFF="./pdiff/perceptualdiff"
+
+# Returns 1 if images are different, 0 if they're essentially identical
+images_differ() {
+    # Check if bytewise identical
+    if cmp --silent "${1}" "${2}"; then
+	# Images are identical
+	return 0
+    fi
+
+    # Run perceptualdiff with minimum threshold
+    pdiff_output=$($PDIFF "${1}" "${2}" -threshold 1)
+    result=${pdiff_output%:*}
+    notes=$(echo "${pdiff_output#*: }" | tail -n 1)
+    if [ "$result" = "PASS" ] && [ "$notes" = "Images are binary identical" ]; then
+	return 0
+    fi
+
+    return 1
+}
+
+# ----------------------------------------------------------------------
+# pixman-downscale images
+#
+# The *-95 tests check rendering at a difficult to downsize dimension.
+# The border pixels between different colored areas can be blurred in
+# different ways resulting in some color variation that is acceptable
+# but throws off the testsuite.  So a visual check is sufficient to
+# verify the results aren't crazily off.
+
+# Use the ARGB32 format of the image file as the main reference
+for file in $(ls ./output/pixman-downscale-*-95.image.argb32.out.png); do
+    dest=$(basename ${file/.image.argb32.out./.ref.})
+    echo "$file -> ./reference/${dest}"
+    cp $file ./reference/${dest}
+done
+echo
+
+# If the ARGB32 format of a given backend's file differs from the main reference,
+# then use it as the backend reference
+for file in $(ls ./output/pixman-downscale-*-95.*.argb32.out.png); do
+    ref=$(basename ${file/-95.*.argb32.out.png/-95.ref.png})
+    if ! images_differ "./reference/${ref}" "${file}"; then
+	dest=$(basename ${file/.argb32.out.png/.ref.png})
+	echo "${file} -> ./reference/${dest}"
+	cp ${file} ./reference/${dest}
+    fi
+done
+echo
+
+# If the RGB24 format differs from existing ref image, then use it as a ref.
+for file in $(ls ./output/pixman-downscale-*-95.*.rgb24.out.png); do
+    ref=$(basename ${file/.rgb24.out.png/.ref.png})
+    if [ ! -e "./reference/${ref}" ]; then
+	ref=$(basename ${file/-95.*.rgb24.out.png/-95.ref.png})
+    fi
+
+    if ! images_differ "./reference/${ref}" "${file}"; then
+	dest=$(basename ${file/.rgb24.out.png/.rgb24.ref.png})
+	echo "${file} -> ./reference/${dest}"
+	cp ${file} ./reference/${dest}
+    fi
+done
-- 
1.7.9.5