Simplify feature checking, fix transparent webp detection, add webpmux detection

PIL/features.py

@@ -6,41 +6,22 @@ modules = {
     "freetype2": "PIL._imagingft",
     "littlecms2": "PIL._imagingcms",
     "webp": "PIL._webp",
-    "transp_webp": ("WEBP", "WebPDecoderBuggyAlpha")
 }
 
-
 def check_module(feature):
-    if feature not in modules:
+    if not (feature in modules):
         raise ValueError("Unknown module %s" % feature)
 
     module = modules[feature]
 
-    method_to_call = None
-    if isinstance(module, 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
-
+    except ImportError:
+        return False
 
 def get_supported_modules():
-    supported_modules = []
-    for feature in modules:
-        if check_module(feature):
-            supported_modules.append(feature)
-    return supported_modules
+    return [f for f in modules if check_module(f)]
 
 codecs = {
     "jpg": "jpeg",
@@ -49,7 +30,6 @@ codecs = {
     "libtiff": "libtiff"
 }
 
-
 def check_codec(feature):
     if feature not in codecs:
         raise ValueError("Unknown codec %s" % feature)
@@ -60,8 +40,38 @@ def check_codec(feature):
 
 
 def get_supported_codecs():
-    supported_codecs = []
-    for feature in codecs:
-        if check_codec(feature):
-            supported_codecs.append(feature)
-    return supported_codecs
+    return [f for f in codecs if check_codec(f)]
+
+features = {
+    "webp_mux": ("PIL._webp", 'HAVE_WEBPMUX'),
+    "transp_webp": ("PIL._webp", "HAVE_TRANSPARENCY"),
+}
+
+def check_feature(feature):
+    if feature not in features:
+        raise ValueError("Unknown feature %s" % feature)
+
+    module, flag = features[feature]
+    
+    try:
+        imported_module = __import__(module, fromlist=['PIL'])
+        return getattr(imported_module, flag)
+    except ImportError:
+        return None
+
+
+def get_supported_features():
+    return [f for f in features if check_feature(f)]
+
+
+def check(feature):
+    return (feature in modules and check_module(feature) or \
+            feature in codecs and check_codec(feature) or \
+            feature in features and check_feature(feature))
+
+def get_supported():
+    ret = get_supported_modules()
+    ret.extend(get_supported_features())
+    ret.extend(get_supported_codecs())
+    return ret
+        

_webp.c

@@ -247,8 +247,12 @@ PyObject* WebPDecoderVersion_wrapper(PyObject* self, PyObject* args){
  * The version of webp that ships with (0.1.3) Ubuntu 12.04 doesn't handle alpha well.
  * Files that are valid with 0.3 are reported as being invalid.
  */
+int WebPDecoderBuggyAlpha() {
+    return WebPGetDecoderVersion()==0x0103;
+}
+
 PyObject* WebPDecoderBuggyAlpha_wrapper(PyObject* self, PyObject* args){
-    return Py_BuildValue("i", WebPGetDecoderVersion()==0x0103);
+    return Py_BuildValue("i", WebPDecoderBuggyAlpha());
 }
 
 static PyMethodDef webpMethods[] =
@@ -268,6 +272,11 @@ void addMuxFlagToModule(PyObject* m) {
 #endif
 }
 
+void addTransparencyFlagToModule(PyObject* m) {
+    PyModule_AddObject(m, "HAVE_TRANSPARENCY",
+		       PyBool_FromLong(!WebPDecoderBuggyAlpha()));
+}
+
 
 #if PY_VERSION_HEX >= 0x03000000
 PyMODINIT_FUNC
@@ -284,6 +293,7 @@ PyInit__webp(void) {
 
     m = PyModule_Create(&module_def);
     addMuxFlagToModule(m);
+    addTransparencyFlagToModule(m);
     return m;
 }
 #else
@@ -292,5 +302,6 @@ init_webp(void)
 {
     PyObject* m = Py_InitModule("_webp", webpMethods);
     addMuxFlagToModule(m);
+    addTransparencyFlagToModule(m);
 }
 #endif

selftest.py

@@ -178,25 +178,14 @@ if __name__ == "__main__":
         ("freetype2", "FREETYPE2"),
         ("littlecms2", "LITTLECMS2"),
         ("webp", "WEBP"),
-        ("transp_webp", "Transparent WEBP")
-    ]:
-        supported = features.check_module(name)
-
-        if supported is None:
-            # A method was being tested, but the module required
-            # for the method could not be correctly imported
-            pass
-        elif supported:
-            print("---", feature, "support ok")
-        else:
-            print("***", feature, "support not installed")
-    for name, feature in [
+        ("transp_webp", "Transparent WEBP"),
+        ("webp_mux", "WEBPMUX"),
         ("jpg", "JPEG"),
         ("jpg_2000", "OPENJPEG (JPEG2000)"),
         ("zlib", "ZLIB (PNG/ZIP)"),
         ("libtiff", "LIBTIFF")
     ]:
-        if features.check_codec(name):
+        if features.check(name):
             print("---", feature, "support ok")
         else:
             print("***", feature, "support not installed")