Merge pull request #3501 from pirate486743186/patch-2

Add APNG extension to PNG plugin

Tests/test_file_png.py

@@ -6,6 +6,12 @@ from io import BytesIO
 import zlib
 import sys
 
+try:
+    from PIL import _webp
+    HAVE_WEBP = True
+except ImportError:
+    HAVE_WEBP = False
+
 codecs = dir(Image.core)
 
 
@@ -579,6 +585,13 @@ class TestFilePng(PillowTestCase):
         self.assertIsInstance(im.text, dict)
         ImageFile.LOAD_TRUNCATED_IMAGES = False
 
+    @unittest.skipUnless(HAVE_WEBP and _webp.HAVE_WEBPANIM,
+                         "WebP support not installed with animation")
+    def test_apng(self):
+        im = Image.open("Tests/images/iss634.apng")
+        expected = Image.open("Tests/images/iss634.webp")
+        self.assert_image_similar(im, expected, 0.23)
+
 
 @unittest.skipIf(sys.platform.startswith('win32'), "requires Unix or macOS")
 class TestTruncatedPngPLeaks(PillowLeakTestCase):

src/PIL/PngImagePlugin.py

@@ -526,6 +526,19 @@ class PngStream(ChunkStream):
 
         return s
 
+    # APNG chunks
+    def chunk_acTL(self, pos, length):
+        s = ImageFile._safe_read(self.fp, length)
+        return s
+
+    def chunk_fcTL(self, pos, length):
+        s = ImageFile._safe_read(self.fp, length)
+        return s
+
+    def chunk_fdAT(self, pos, length):
+        s = ImageFile._safe_read(self.fp, length)
+        return s
+
 
 # --------------------------------------------------------------------
 # PNG reader
@@ -892,6 +905,7 @@ def getchunks(im, **params):
 Image.register_open(PngImageFile.format, PngImageFile, _accept)
 Image.register_save(PngImageFile.format, _save)
 
-Image.register_extension(PngImageFile.format, ".png")
+Image.register_extensions(PngImageFile.format, [".png", ".apng"])
 
 Image.register_mime(PngImageFile.format, "image/png")
+Image.register_mime(PngImageFile.format, "image/apng")