tests/test_annots.py: test_1645(): use gentle_compare.pixmaps_rms() instead of direct comparison.

Avoids spurious failures from harmless mupdf changes.

Author: julian-smith-artifex-com

tests/test_annots.py

@@ -257,11 +257,13 @@ def test_1645():
                 )
         doc.save(path_out, garbage=1, deflate=True, no_new_id=True)
         print(f'Have created {path_out}. comparing with {path_expected}.')
-        with open( path_out, 'rb') as f:
-            out = f.read()
-        with open( path_expected, 'rb') as f:
-            expected = f.read()
-        assert out == expected, f'Files differ: {path_out} {path_expected}'
+        with pymupdf.open(path_expected) as doc_expected, pymupdf.open(path_out) as doc_out:
+            rms = gentle_compare.pixmaps_rms(
+                    doc_expected[0].get_pixmap(),
+                    doc_out[0].get_pixmap(),
+                    )
+        print(f'test_1645: {rms=}')
+        assert rms < 0.1, f'Pixmaps differ: {path_expected=} {path_out=}'
     finally:
         # Restore annot_stem.
         pymupdf.TOOLS.set_annot_stem(annot_stem)