Added has_transparency_data()

Tests/test_image.py

@@ -906,6 +906,31 @@ class TestImage:
         im = Image.new("RGB", size)
         assert im.tobytes() == b""
 
+    def test_has_transparency_data(self):
+        for mode in ("1", "L", "P", "RGB"):
+            im = Image.new(mode, (1, 1))
+            assert not im.has_transparency_data()
+
+        for mode in ("LA", "La", "PA", "RGBA", "RGBa"):
+            im = Image.new(mode, (1, 1))
+            assert im.has_transparency_data()
+
+        # P mode with "transparency" info
+        with Image.open("Tests/images/first_frame_transparency.gif") as im:
+            assert "transparency" in im.info
+            assert im.has_transparency_data()
+
+        # RGB mode with "transparency" info
+        with Image.open("Tests/images/rgb_trns.png") as im:
+            assert "transparency" in im.info
+            assert im.has_transparency_data()
+
+        # P mode with RGBA palette
+        im = Image.new("RGBA", (1, 1)).convert("P")
+        assert im.mode == "P"
+        assert im.palette.mode == "RGBA"
+        assert im.has_transparency_data()
+
     def test_apply_transparency(self):
         im = Image.new("P", (1, 1))
         im.putpalette((0, 0, 0, 1, 1, 1))

docs/reference/Image.rst

@@ -195,6 +195,7 @@ This helps to get the bounding box coordinates of the input image::
 .. automethod:: PIL.Image.Image.getpalette
 .. automethod:: PIL.Image.Image.getpixel
 .. automethod:: PIL.Image.Image.getprojection
+.. automethod:: PIL.Image.Image.has_transparency_data
 .. automethod:: PIL.Image.Image.histogram
 .. automethod:: PIL.Image.Image.paste
 .. automethod:: PIL.Image.Image.point

src/PIL/Image.py

@@ -915,7 +915,7 @@ class Image:
 
         self.load()
 
-        has_transparency = self.info.get("transparency") is not None
+        has_transparency = "transparency" in self.info
         if not mode and self.mode == "P":
             # determine default mode
             if self.palette:
@@ -1531,6 +1531,23 @@ class Image:
             rawmode = mode
         return list(self.im.getpalette(mode, rawmode))
 
+    def has_transparency_data(self):
+        """
+        Determine if an image has transparency data, whether in the form of an
+        alpha channel, a palette with an alpha channel, or a "transparency" key
+        in the info dictionary.
+
+        Note the image might still appear solid, if all of the values shown
+        within are opaque.
+
+        :returns: A boolean.
+        """
+        return (
+            self.mode in ("LA", "La", "PA", "RGBA", "RGBa")
+            or (self.mode == "P" and self.palette.mode == "RGBA")
+            or "transparency" in self.info
+        )
+
     def apply_transparency(self):
         """
         If a P mode image has a "transparency" key in the info dictionary,