Allow loading of WMF images at a given DPI

Tests/test_file_wmf.py

@@ -53,6 +53,17 @@ class TestFileWmf(PillowTestCase):
         with Image.open("Tests/images/drawing_roundDown.emf") as im:
             self.assertEqual(im.info["dpi"], 1426)
 
+    def test_load_set_dpi(self):
+        with Image.open("Tests/images/drawing.wmf") as im:
+            self.assertEquals(im.size, (82, 82))
+
+            if hasattr(Image.core, "drawwmf"):
+                im.load(144)
+                self.assertEquals(im.size, (164, 164))
+
+                with Image.open("Tests/images/drawing_wmf_ref_144.png") as expected:
+                    self.assert_image_similar(im, expected, 2.0)
+
     def test_save(self):
         im = hopper()
 

src/PIL/WmfImagePlugin.py

@@ -78,6 +78,7 @@ class WmfStubImageFile(ImageFile.StubImageFile):
     format_description = "Windows Metafile"
 
     def _open(self):
+        self._inch = None
 
         # check placable header
         s = self.fp.read(80)
@@ -87,7 +88,7 @@ class WmfStubImageFile(ImageFile.StubImageFile):
             # placeable windows metafile
 
             # get units per inch
-            inch = word(s, 14)
+            self._inch = word(s, 14)
 
             # get bounding box
             x0 = short(s, 6)
@@ -96,12 +97,14 @@ class WmfStubImageFile(ImageFile.StubImageFile):
             y1 = short(s, 12)
 
             # normalize size to 72 dots per inch
-            size = (x1 - x0) * 72 // inch, (y1 - y0) * 72 // inch
+            self.info["dpi"] = 72
+            size = (
+                (x1 - x0) * self.info["dpi"] // self._inch,
+                (y1 - y0) * self.info["dpi"] // self._inch,
+            )
 
             self.info["wmf_bbox"] = x0, y0, x1, y1
 
-            self.info["dpi"] = 72
-
             # sanity check (standard metafile header)
             if s[22:26] != b"\x01\x00\t\x00":
                 raise SyntaxError("Unsupported WMF file format")
@@ -118,7 +121,6 @@ class WmfStubImageFile(ImageFile.StubImageFile):
             # get frame (in 0.01 millimeter units)
             frame = _long(s, 24), _long(s, 28), _long(s, 32), _long(s, 36)
 
-            # normalize size to 72 dots per inch
             size = x1 - x0, y1 - y0
 
             # calculate dots per inch from bbox and frame
@@ -145,6 +147,16 @@ class WmfStubImageFile(ImageFile.StubImageFile):
     def _load(self):
         return _handler
 
+    def load(self, dpi=None):
+        if dpi is not None and self._inch is not None:
+            self.info["dpi"] = int(dpi + 0.5)
+            x0, y0, x1, y1 = self.info["wmf_bbox"]
+            self._size = (
+                (x1 - x0) * self.info["dpi"] // self._inch,
+                (y1 - y0) * self.info["dpi"] // self._inch,
+            )
+        super().load()
+
 
 def _save(im, fp, filename):
     if _handler is None or not hasattr(_handler, "save"):