Merge pull request #1233 from radarhere/features

Separated out feature checking from selftest

PIL/features.py

@@ -0,0 +1,67 @@
+from PIL import Image
+
+modules = {
+    "pil": "PIL._imaging",
+    "tkinter": "PIL._imagingtk",
+    "freetype2": "PIL._imagingft",
+    "littlecms2": "PIL._imagingcms",
+    "webp": "PIL._webp",
+    "transp_webp": ("WEBP", "WebPDecoderBuggyAlpha")
+}
+
+
+def check_module(feature):
+    if feature not in modules:
+        raise ValueError("Unknown module %s" % feature)
+
+    module = modules[feature]
+
+    method_to_call = None
+    if type(module) is tuple:
+        module, method_to_call = module
+
+    try:
+        imported_module = __import__(module)
+    except ImportError:
+        # If a method is being checked, None means that
+        # rather than the method failing, the module required for the method
+        # failed to be imported first
+        return None if method_to_call else False
+
+    if method_to_call:
+        method = getattr(imported_module, method_to_call)
+        return method() is True
+    else:
+        return True
+
+
+def get_supported_modules():
+    supported_modules = []
+    for feature in modules:
+        if check_module(feature):
+            supported_modules.append(feature)
+    return supported_modules
+
+codecs = {
+    "jpg": "jpeg",
+    "jpg_2000": "jpeg2k",
+    "zlib": "zip",
+    "libtiff": "libtiff"
+}
+
+
+def check_codec(feature):
+    if feature not in codecs:
+        raise ValueError("Unknown codec %s" % feature)
+
+    codec = codecs[feature]
+
+    return codec + "_encoder" in dir(Image.core)
+
+
+def get_supported_codecs():
+    supported_codecs = []
+    for feature in codecs:
+        if check_codec(feature):
+            supported_codecs.append(feature)
+    return supported_codecs

Tests/test_features.py

@@ -0,0 +1,35 @@
+from helper import unittest, PillowTestCase
+
+from PIL import features
+
+
+class TestFeatures(PillowTestCase):
+
+    def test_check_features(self):
+        for feature in features.modules:
+            self.assertTrue(
+                features.check_module(feature) in [True, False, None])
+        for feature in features.codecs:
+            self.assertTrue(features.check_codec(feature) in [True, False])
+
+    def test_supported_features(self):
+        self.assertTrue(type(features.get_supported_modules()) is list)
+        self.assertTrue(type(features.get_supported_codecs()) is list)
+
+    def test_unsupported_codec(self):
+        # Arrange
+        codec = "unsupported_codec"
+        # Act / Assert
+        self.assertRaises(ValueError, lambda: features.check_codec(codec))
+
+    def test_unsupported_module(self):
+        # Arrange
+        module = "unsupported_module"
+        # Act / Assert
+        self.assertRaises(ValueError, lambda: features.check_module(module))
+
+
+if __name__ == '__main__':
+    unittest.main()
+
+# End of file

selftest.py

@@ -9,6 +9,7 @@ if "--installed" in sys.argv:
     del sys.path[0]
 
 from PIL import Image, ImageDraw, ImageFilter, ImageMath
+from PIL import features
 
 if "--installed" in sys.argv:
     sys.path.insert(0, sys_path_0)
@@ -162,22 +163,6 @@ def testimage():
     """
 
 
-def check_module(feature, module):
-    try:
-        __import__(module)
-    except ImportError:
-        print("***", feature, "support not installed")
-    else:
-        print("---", feature, "support ok")
-
-
-def check_codec(feature, codec):
-    if codec + "_encoder" not in dir(Image.core):
-        print("***", feature, "support not installed")
-    else:
-        print("---", feature, "support ok")
-
-
 if __name__ == "__main__":
     # check build sanity
 
@@ -189,23 +174,34 @@ if __name__ == "__main__":
     print("Python modules loaded from", os.path.dirname(Image.__file__))
     print("Binary modules loaded from", os.path.dirname(Image.core.__file__))
     print("-"*68)
-    check_module("PIL CORE", "PIL._imaging")
+    for name, feature in [
-    check_module("TKINTER", "PIL._imagingtk")
+        ("pil", "PIL CORE"),
-    check_codec("JPEG", "jpeg")
+        ("tkinter", "TKINTER"),
-    check_codec("JPEG 2000", "jpeg2k")
+        ("freetype2", "FREETYPE2"),
-    check_codec("ZLIB (PNG/ZIP)", "zip")
+        ("littlecms2", "LITTLECMS2"),
-    check_codec("LIBTIFF", "libtiff")
+        ("webp", "WEBP"),
-    check_module("FREETYPE2", "PIL._imagingft")
+        ("transp_webp", "Transparent WEBP")
-    check_module("LITTLECMS2", "PIL._imagingcms")
+    ]:
-    check_module("WEBP", "PIL._webp")
+        supported = features.check_module(name)
-    try:
+
-        from PIL import _webp
+        if supported is None:
-        if _webp.WebPDecoderBuggyAlpha():
+            # A method was being tested, but the module required
-            print("***", "Transparent WEBP", "support not installed")
+            # for the method could not be correctly imported
+            pass
+        elif supported:
+            print("---", feature, "support ok")
         else:
-            print("---", "Transparent WEBP", "support ok")
+            print("***", feature, "support not installed")
-    except Exception:
+    for name, feature in [
-        pass
+        ("jpg", "JPEG"),
+        ("jpg_2000", "OPENJPEG (JPEG2000)"),
+        ("zlib", "ZLIB (PNG/ZIP)"),
+        ("libtiff", "LIBTIFF")
+    ]:
+        if features.check_codec(name):
+            print("---", feature, "support ok")
+        else:
+            print("***", feature, "support not installed")
     print("-"*68)
 
     # use doctest to make sure the test program behaves as documented!