BUG: Page.scale now also scales the cropbox

Closes #272

Co-authored-by: Henri Salo <henri.salo@nixu.com>

PyPDF2/_page.py

@@ -897,18 +897,15 @@ def scale(self, sx: float, sy: float) -> None:
         Scale a page by the given factors by applying a transformation
         matrix to its content and updating the page size.
 
+        This updates the mediabox, the cropbox, and the contents
+        of the page.
+
         :param float sx: The scaling factor on horizontal axis.
         :param float sy: The scaling factor on vertical axis.
         """
         self.add_transformation((sx, 0, 0, sy, 0, 0))
-        self.mediabox = RectangleObject(
-            (
-                float(self.mediabox.left) * sx,
-                float(self.mediabox.bottom) * sy,
-                float(self.mediabox.right) * sx,
-                float(self.mediabox.top) * sy,
-            )
-        )
+        self.mediabox = self.mediabox.scale(sx, sy)
+        self.cropbox = self.cropbox.scale(sx, sy)
         if PG.VP in self:
             viewport = self[PG.VP]
             if isinstance(viewport, ArrayObject):

PyPDF2/generic.py

@@ -1360,6 +1360,16 @@ def _ensure_is_number(self, value: Any) -> Union[FloatObject, NumberObject]:
             value = FloatObject(value)
         return value
 
+    def scale(self, sx: float, sy: float) -> "RectangleObject":
+        return RectangleObject(
+            (
+                float(self.left) * sx,
+                float(self.bottom) * sy,
+                float(self.right) * sx,
+                float(self.top) * sy,
+            )
+        )
+
     def ensureIsNumber(
         self, value: Any
     ) -> Union[FloatObject, NumberObject]:  # pragma: no cover