Don’t resize the same image twice when the --dpi option is set

It also avoids crashes with PNG images, as the incomplete PNG part used in the
PDF was read by Pillow the second time instead of the whole PNG file.

weasyprint/images.py

@@ -94,28 +94,17 @@ def draw(self, stream, concrete_width, concrete_height, image_rendering):
             return
 
         width, height = self.width, self.height
+        interpolate = 'true' if image_rendering == 'auto' else 'false'
+        ratio = 1
         if self._dpi:
             pt_to_in = 4 / 3 / 96
             width_inches = abs(concrete_width * stream.ctm[0][0] * pt_to_in)
             height_inches = abs(concrete_height * stream.ctm[1][1] * pt_to_in)
             dpi = max(self.width / width_inches, self.height / height_inches)
             if dpi > self._dpi:
                 ratio = self._dpi / dpi
-                image = Image.open(io.BytesIO(self.image_data.data))
-                width = int(round(self.width * ratio))
-                height = int(round(self.height * ratio))
-                image.thumbnail((max(1, width), max(1, height)))
-                image_file = io.BytesIO()
-                image.save(
-                    image_file, format=image.format, optimize=self.optimize)
-                width, height = image.width, image.height
-                self.image_data = self.cache_image_data(image_file.getvalue())
-        else:
-            dpi = None
-
-        interpolate = 'true' if image_rendering == 'auto' else 'false'
+        image_name = stream.add_image(self, width, height, interpolate, ratio)
 
-        image_name = stream.add_image(self, width, height, interpolate)
         stream.transform(
             concrete_width, 0, 0, -concrete_height, 0, concrete_height)
         stream.draw_x_object(image_name)

weasyprint/pdf/stream.py

@@ -8,6 +8,7 @@
 from fontTools import subset
 from fontTools.ttLib import TTFont, TTLibError, ttFont
 from fontTools.varLib.mutator import instantiateVariableFont
+from PIL import Image
 
 from ..logger import LOGGER
 from ..matrix import Matrix
@@ -361,13 +362,24 @@ def add_group(self, x, y, width, height):
         self._x_objects[group.id] = group
         return group
 
-    def add_image(self, image, width, height, interpolate):
-        image_name = f'i{image.id}{width}{height}{interpolate}'
+    def add_image(self, image, width, height, interpolate, ratio):
+        image_name = f'i{image.id}{width}{height}{interpolate}{ratio}'
         self._x_objects[image_name] = None  # Set by write_pdf
         if image_name in self._images:
             # Reuse image already stored in document
             return image_name
 
+        if ratio != 1:
+            thumbnail = Image.open(io.BytesIO(image.image_data.data))
+            width = int(round(image.width * ratio))
+            height = int(round(image.height * ratio))
+            thumbnail.thumbnail((max(1, width), max(1, height)))
+            image_file = io.BytesIO()
+            thumbnail.save(
+                image_file, format=thumbnail.format, optimize=image.optimize)
+            width, height = thumbnail.width, thumbnail.height
+            image.image_data = image.cache_image_data(image_file.getvalue())
+
         xobject = image.get_xobject(width, height, interpolate)
         self._images[image_name] = xobject
         return image_name