regtest: Use diff.png extension for image diff files

So that they are recognized as images

4 files changed, 17 insertions, 5 deletions

diff --git a/regtest/backends/__init__.py b/regtest/backends/__init__.py
index 47985fbc..77e5498d 100644
--- a/regtest/backends/__init__.py
+++ b/regtest/backends/__init__.py
@@ -33,13 +33,17 @@ class UnknownBackendError(Exception):
 
 class Backend:
 
-    def __init__(self, name):
+    def __init__(self, name, diff_ext = None):
         self._name = name
+        self._diff_ext = diff_ext
         self._utilsdir = Config().utils_dir
 
     def get_name(self):
         return self._name
 
+    def get_diff_ext(self):
+        return self._diff_ext
+
     def __should_have_checksum(self, entry):
         if not entry.startswith(self._name):
             return False
@@ -155,6 +159,14 @@ class Backend:
     def has_stderr(self, test_path):
         return os.path.exists(os.path.join(test_path, self._name + '.stderr'))
 
+    def has_diff(self, test_result):
+        if not self._diff_ext:
+            return False
+        basename = os.path.basename(test_result)
+        if not basename.startswith(self._name):
+            return False
+        return os.path.exists(test_result + self._diff_ext)
+
     def __create_stderr_file(self, stderr, out_path):
         if not stderr:
             return
@@ -216,7 +228,7 @@ class Backend:
         ref = Image.open(ref_path)
         result = Image.open(result_path)
         diff = ImageChops.difference(ref, result)
-        diff.save(result_path + '.diff', 'png')
+        diff.save(result_path + '.diff.png', 'png')
 
     def _create_diff(self, ref_path, result_path):
         raise NotImplementedError
diff --git a/regtest/backends/cairo.py b/regtest/backends/cairo.py
index a990ddf7..304783ea 100644
--- a/regtest/backends/cairo.py
+++ b/regtest/backends/cairo.py
@@ -23,7 +23,7 @@ import os
 class Cairo(Backend):
 
     def __init__(self, name):
-        Backend.__init__(self, name)
+        Backend.__init__(self, name, '.diff.png')
         self._pdftocairo = os.path.join(self._utilsdir, 'pdftocairo');
 
     def create_refs(self, doc_path, refs_path):
diff --git a/regtest/backends/splash.py b/regtest/backends/splash.py
index 5fbfba62..3144bc75 100644
--- a/regtest/backends/splash.py
+++ b/regtest/backends/splash.py
@@ -23,7 +23,7 @@ import os
 class Splash(Backend):
 
     def __init__(self, name):
-        Backend.__init__(self, name)
+        Backend.__init__(self, name, '.diff.png')
         self._pdftoppm = os.path.join(self._utilsdir, 'pdftoppm');
 
     def create_refs(self, doc_path, refs_path):
diff --git a/regtest/backends/text.py b/regtest/backends/text.py
index 14e7c030..10b660a3 100644
--- a/regtest/backends/text.py
+++ b/regtest/backends/text.py
@@ -23,7 +23,7 @@ import os
 class Text(Backend):
 
     def __init__(self, name):
-        Backend.__init__(self, name)
+        Backend.__init__(self, name, '.diff')
         self._pdftotext = os.path.join(self._utilsdir, 'pdftotext');
 
     def create_refs(self, doc_path, refs_path):