Fix #2596

When continuing to use a page object after the PDF has been saved with garbage options may change the MuPDF cache such that e.g. rendering the page after the save will produce wrong appearance or even garbled appearance.
The user needs to reload the page (page = doc.reload(page)) before using it further, especially for rendering.
The reload method now always empties the cache.

fitz/fitz.i

@@ -4625,6 +4625,7 @@ if basestate:
                     old_annots[k] = v
                 page._erase()  # remove the page
                 page = None
+                TOOLS.store_shrink(100)
                 page = self.load_page(pno)  # reload the page
 
                 # copy annot refs over to the new dictionary

src/__init__.py

@@ -5042,6 +5042,7 @@ def reload_page(self, page: "struct Page *") -> "struct Page *":
             old_annots[k] = v
         page._erase()  # remove the page
         page = None
+        TOOLS.store_shrink(100)
         page = self.load_page(pno)  # reload the page
 
         # copy annot refs over to the new dictionary

tests/test_general.py

@@ -539,3 +539,17 @@ def test_2692():
                 clip=fitz.Rect(0,0,10,10),
                 )
 
+
+def test_2596():
+    """Cconfirm correctly abandoning cache when reloading a page."""
+    doc = fitz.Document("resources/test_2596.pdf")
+    page = doc[0]
+    pix0 = page.get_pixmap()  # render the page
+    _ = doc.tobytes(garbage=3)  # save with garbage collection
+
+    # Note this will invalidate cache content for this page.
+    # Reloading the page now empties the cache, so rendering
+    # will deliver the same pixmap
+    page = doc.reload_page(page)
+    pix1 = page.get_pixmap()
+    assert pix1.samples == pix0.samples