From 27134340f598e480db9c50799896325a3d5aa7ed Mon Sep 17 00:00:00 2001
From: Andrew Murray <radarhere@users.noreply.github.com>
Date: Thu, 2 May 2019 19:46:17 +1000
Subject: [PATCH] Expand GIF to include frames with extents outside the image
 size

---
 Tests/images/test_extents.gif | Bin 0 -> 368 bytes
 Tests/test_file_gif.py        |   6 ++++++
 src/PIL/GifImagePlugin.py     |   2 ++
 3 files changed, 8 insertions(+)
 create mode 100644 Tests/images/test_extents.gif

diff --git a/Tests/images/test_extents.gif b/Tests/images/test_extents.gif
new file mode 100644
index 0000000000000000000000000000000000000000..03c436435d6d18bcb407d39374f34afd22be7ff1
GIT binary patch
literal 368
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zqNCjs##whxY+QW2U%|Oc#&gq>lan=qSH+y%wDk0JgXB|lJU1^pJKLi8)t!@@m!F^S
z(99+4wPnS{#U7KjVoz;Zd3kxjVz0SgTUT9O9kDs<?y0S-udh!y+$HP1ZOzTi8JAbZ
zp5C_h_V$9ur{;QZUw3zR#phRdPj6p;e}4lrx17(84G#}@2y4fki70Sj&@o~#8al4E
F1^|#9wif^Z

literal 0
HcmV?d00001

diff --git a/Tests/test_file_gif.py b/Tests/test_file_gif.py
index 8388949888d..f9c31212469 100644
--- a/Tests/test_file_gif.py
+++ b/Tests/test_file_gif.py
@@ -663,3 +663,9 @@ def test_lzw_bits(self):
         self.assertEqual(im.tile[0][3][0], 11)  # LZW bits
         # codec error prepatch
         im.load()
+
+    def test_extents(self):
+        im = Image.open('Tests/images/test_extents.gif')
+        self.assertEqual(im.size, (100, 100))
+        im.seek(1)
+        self.assertEqual(im.size, (150, 150))
diff --git a/src/PIL/GifImagePlugin.py b/src/PIL/GifImagePlugin.py
index 3dc13ac0392..5605b558147 100644
--- a/src/PIL/GifImagePlugin.py
+++ b/src/PIL/GifImagePlugin.py
@@ -233,6 +233,8 @@ def _seek(self, frame):
                 # extent
                 x0, y0 = i16(s[0:]), i16(s[2:])
                 x1, y1 = x0 + i16(s[4:]), y0 + i16(s[6:])
+                if x1 > self.size[0] or y1 > self.size[1]:
+                    self._size = max(x1, self.size[0]), max(y1, self.size[1])
                 self.dispose_extent = x0, y0, x1, y1
                 flags = i8(s[8])