Remove transparency if it cannot be remapped

python-pillow · May 21, 2022 · 99f4623 · 99f4623
1 parent 46a80d1
commit 99f4623
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Showing 2 changed files with 19 additions and 1 deletion.
diff --git a/Tests/test_image.py b/Tests/test_image.py
@@ -607,6 +607,20 @@ def test_remap_palette(self):
             with pytest.raises(ValueError):
                 im.remap_palette(None)
 
+    def test_remap_palette_transparency(self):
+        im = Image.new("P", (1, 2))
+        im.putpixel((0, 1), 1)
+        im.info["transparency"] = 0
+
+        im_remapped = im.remap_palette([1, 0])
+        assert im_remapped.info["transparency"] == 1
+
+        # Test unused transparency
+        im.info["transparency"] = 2
+
+        im_remapped = im.remap_palette([1, 0])
+        assert "transparency" not in im_remapped.info
+
     def test__new(self):
         im = hopper("RGB")
         im_p = hopper("P")

diff --git a/src/PIL/Image.py b/src/PIL/Image.py
@@ -1935,7 +1935,11 @@ def remap_palette(self, dest_map, source_palette=None):
         m_im.palette = ImagePalette.ImagePalette("RGB", palette=palette_bytes)
 
         if "transparency" in self.info:
-            m_im.info["transparency"] = new_positions[self.info["transparency"]]
+            try:
+                m_im.info["transparency"] = dest_map.index(self.info["transparency"])
+            except ValueError:
+                if "transparency" in m_im.info:
+                    del m_im.info["transparency"]
 
         return m_im