Improve encryption tests; drop some public domain resources

Generate the encrypted files we need and remove special test files we retained for this.

Replace jbig2.pdf based on congress.jpg with version based on ccitt.pdf.

tests/resources/README.rst

@@ -111,14 +111,12 @@ These test resources are assemblies or derivatives from other previously mention
 - baiona_alpha.png (from baiona.png, RGB+A version)
 - cardinal.pdf (four cardinal directions, baked-in rotated copies of linn.png)
 - ccitt.pdf (linn.png, converted to CCITT encoding)
-- encrypted_algo4.pdf (congress.jpg, encrypted with algorithm 4 - not supported by PyPDF2)
 - graph_ocred.pdf (from graph.pdf)
 - jbig2.pdf (congress.jpg, converted to JBIG2 encoding)
 - multipage.pdf (from several other files)
 - palette.pdf (congress.jpg, converted to a 256-color palette)
 - poster.pdf (from linn.png)
 - rotated_skew.pdf (a /Rotate'd and skewed document from linn.png)
-- skew-encrypted.pdf (skew.pdf with encryption - access supported by PyPDF2, password is "password")
 - skew.pdf (from linn.png, skew simulated by adjusting the transformation matrix)
 - toc.pdf (from formxobject.pdf, trivial.pdf)
 

tests/test_main.py

@@ -292,12 +292,6 @@ def test_input_file_not_a_pdf(caplog, no_outpdf):
         assert input_file in caplog.text
 
 
-def test_encrypted(resources, caplog, no_outpdf):
-    result = run_ocrmypdf_api(resources / 'skew-encrypted.pdf', no_outpdf)
-    assert result == ExitCode.encrypted_pdf
-    assert 'encryption must be removed' in caplog.text
-
-
 @pytest.mark.parametrize('renderer', RENDERERS)
 def test_pagesegmode(renderer, resources, outpdf):
     check_ocrmypdf(
@@ -398,14 +392,27 @@ def test_tesseract_image_too_big(renderer, resources, outpdf):
     )
 
 
-def test_algo4(resources, outpdf):
-    p = run_ocrmypdf(
-        resources / 'encrypted_algo4.pdf',
+@pytest.mark.parametrize('encryption_level', [2, 3, 4, 6])
+def test_encrypted(resources, outpdf, encryption_level, caplog):
+    encryption = pikepdf.models.encryption.Encryption(
+        owner='ocrmypdf',
+        user='ocrmypdf',
+        R=encryption_level,
+        aes=(encryption_level >= 4),
+        metadata=(encryption_level == 6),
+    )
+
+    with pikepdf.open(resources / 'jbig2.pdf') as pdf:
+        pdf.save(outpdf, encryption=encryption)
+
+    exitcode = run_ocrmypdf_api(
+        outpdf,
         outpdf,
         '--plugin',
         'tests/plugins/tesseract_noop.py',
     )
-    assert p.returncode == ExitCode.encrypted_pdf
+    assert exitcode == ExitCode.encrypted_pdf
+    assert 'encryption must be removed' in caplog.text
 
 
 def test_jbig2_passthrough(resources, outpdf):