Add new --pages feature to limit OCR to only specific pages

tests/test_page_numbers.py

@@ -0,0 +1,56 @@
+# © 2019 James R. Barlow: github.com/jbarlow83
+#
+# This file is part of OCRmyPDF.
+#
+# OCRmyPDF is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# OCRmyPDF is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with OCRmyPDF.  If not, see <http://www.gnu.org/licenses/>.
+
+import pytest
+
+from ocrmypdf import ocrmypdf as run
+from ocrmypdf._validation import _pages_from_ranges
+from ocrmypdf.pdfinfo import PdfInfo
+
+
+def test_str_ranges():
+    assert _pages_from_ranges('43') == {42}
+    assert _pages_from_ranges('1, 2, 3') == {0, 1, 2}
+    assert _pages_from_ranges('1-3') == {0, 1, 2}
+    assert _pages_from_ranges('1-3,5,7,42') == {0, 1, 2, 4, 6, 41}
+    assert _pages_from_ranges('3, 3, 3, 3,') == {2}
+
+
+def test_nonmonotonic_warning(caplog):
+    pages = _pages_from_ranges('1, 3, 2')
+    assert pages == {0, 1, 2}
+    assert 'out of order' in caplog.text
+
+
+def test_list_range():
+    assert _pages_from_ranges([0, 1, 2]) == {0, 1, 2}
+
+
+def test_limited_pages(resources, outpdf, spoof_tesseract_cache):
+    multi = resources / 'multipage.pdf'
+    run(
+        multi,
+        outpdf,
+        pages='5-6',
+        optimize=0,
+        output_type='pdf',
+        tesseract_env=spoof_tesseract_cache,
+    )
+    pi = PdfInfo(outpdf)
+    assert not pi.pages[0].has_text
+    assert pi.pages[4].has_text
+    assert pi.pages[5].has_text