Allow loading of EMF images at a given DPI (#8536)

Co-authored-by: Andrew Murray <[email protected]>

Author: radarhere

Tests/images/drawing_emf_ref_72_144.png

@@ -97,6 +97,20 @@ def test_load_set_dpi() -> None:
 
             assert_image_similar_tofile(im, "Tests/images/drawing_wmf_ref_144.png", 2.1)
 
+    with Image.open("Tests/images/drawing.emf") as im:
+        assert im.size == (1625, 1625)
+
+        if not hasattr(Image.core, "drawwmf"):
+            return
+        im.load(im.info["dpi"])
+        assert im.size == (1625, 1625)
+
+    with Image.open("Tests/images/drawing.emf") as im:
+        im.load((72, 144))
+        assert im.size == (82, 164)
+
+        assert_image_equal_tofile(im, "Tests/images/drawing_emf_ref_72_144.png")
+
 
 @pytest.mark.parametrize("ext", (".wmf", ".emf"))
 def test_save(ext: str, tmp_path: Path) -> None:

Tests/test_file_wmf.py

@@ -80,19 +80,18 @@ class WmfStubImageFile(ImageFile.StubImageFile):
     format_description = "Windows Metafile"
 
     def _open(self) -> None:
-        self._inch = None
-
         # check placable header
         s = self.fp.read(80)
 
         if s.startswith(b"\xd7\xcd\xc6\x9a\x00\x00"):
             # placeable windows metafile
 
             # get units per inch
-            self._inch = word(s, 14)
-            if self._inch == 0:
+            inch = word(s, 14)
+            if inch == 0:
                 msg = "Invalid inch"
                 raise ValueError(msg)
+            self._inch: tuple[float, float] = inch, inch
 
             # get bounding box
             x0 = short(s, 6)
@@ -103,8 +102,8 @@ def _open(self) -> None:
             # normalize size to 72 dots per inch
             self.info["dpi"] = 72
             size = (
-                (x1 - x0) * self.info["dpi"] // self._inch,
-                (y1 - y0) * self.info["dpi"] // self._inch,
+                (x1 - x0) * self.info["dpi"] // inch,
+                (y1 - y0) * self.info["dpi"] // inch,
             )
 
             self.info["wmf_bbox"] = x0, y0, x1, y1
@@ -138,6 +137,7 @@ def _open(self) -> None:
                 self.info["dpi"] = xdpi
             else:
                 self.info["dpi"] = xdpi, ydpi
+            self._inch = xdpi, ydpi
 
         else:
             msg = "Unsupported file format"
@@ -153,13 +153,17 @@ def _open(self) -> None:
     def _load(self) -> ImageFile.StubHandler | None:
         return _handler
 
-    def load(self, dpi: int | None = None) -> Image.core.PixelAccess | None:
-        if dpi is not None and self._inch is not None:
+    def load(
+        self, dpi: float | tuple[float, float] | None = None
+    ) -> Image.core.PixelAccess | None:
+        if dpi is not None:
             self.info["dpi"] = dpi
             x0, y0, x1, y1 = self.info["wmf_bbox"]
+            if not isinstance(dpi, tuple):
+                dpi = dpi, dpi
             self._size = (
-                (x1 - x0) * self.info["dpi"] // self._inch,
-                (y1 - y0) * self.info["dpi"] // self._inch,
+                int((x1 - x0) * dpi[0] / self._inch[0]),
+                int((y1 - y0) * dpi[1] / self._inch[1]),
             )
         return super().load()