Gracefully recover from tesseract's failure to process very large images

And test cases to check this

ocrmypdf/tesseract.py

@@ -98,6 +98,8 @@ def get_orientation(input_file, language: list, timeout: float, log):
         return OrientationConfidence(angle=0, confidence=0.0)
     except CalledProcessError as e:
         tesseract_log_output(log, e.output, input_file)
+        if 'Image too large' in e.output:
+            return OrientationConfidence(0, 0)
         raise e from e
     else:
         osd = {}
@@ -148,6 +150,13 @@ def page_timedout(log, input_file):
     log.warning(prefix + " took too long to OCR - skipping")
 
 
+def _generate_null_hocr(output_hocr, pageinfo):
+    with open(output_hocr, 'w', encoding="utf-8") as f:
+        f.write(HOCR_TEMPLATE.format(
+            pageinfo['width_pixels'],
+            pageinfo['height_pixels']))
+
+
 def generate_hocr(input_file, output_hocr, language: list, tessconfig: list,
                   timeout: float, pageinfo_getter, pagesegmode: int, log):
 
@@ -175,13 +184,13 @@ def generate_hocr(input_file, output_hocr, language: list, tessconfig: list,
         # Temporary workaround to hocrTransform not being able to function if
         # it does not have a valid hOCR file.
         page_timedout(log, input_file)
-        with open(output_hocr, 'w', encoding="utf-8") as f:
-            pageinfo = pageinfo_getter()
-            f.write(HOCR_TEMPLATE.format(
-                pageinfo['width_pixels'],
-                pageinfo['height_pixels']))
+        _generate_null_hocr(output_hocr, pageinfo_getter())
     except CalledProcessError as e:
         tesseract_log_output(log, e.output, input_file)
+        if 'Image too large' in e.output:
+            _generate_null_hocr(output_hocr, pageinfo_getter())
+            return
+
         raise e from e
     else:
         tesseract_log_output(log, stdout, input_file)
@@ -242,6 +251,9 @@ def generate_pdf(input_image, skip_pdf, output_pdf, language: list,
         shutil.copy(skip_pdf, output_pdf)
     except CalledProcessError as e:
         tesseract_log_output(log, e.output, input_image)
+        if 'Image too large' in e.output:
+            shutil.copy(skip_pdf, output_pdf)
+            return
         raise e from e
     else:
         tesseract_log_output(log, stdout, input_image)

tests/spoof/tesseract_big_image_error.py

@@ -0,0 +1,50 @@
+#!/usr/bin/env python3
+import sys
+
+
+VERSION_STRING = '''tesseract 3.04.00
+ leptonica-1.72
+  libjpeg 8d : libpng 1.6.19 : libtiff 4.0.6 : zlib 1.2.5
+SPOOFED: return error claiming image too big
+'''
+
+"""Simulates a Tesseract crash
+
+It isn't strictly necessary to crash the process and that has unwanted
+side effects like triggering core dumps or error reporting, logging and such.
+It's enough to dump some text to stderr and return an error code.
+
+Follows the POSIX? convention of returning 128 + signal number.
+
+"""
+
+
+def main():
+    if sys.argv[1] == '--version':
+        print(VERSION_STRING, file=sys.stderr)
+        sys.exit(0)
+    elif sys.argv[1] == '--list-langs':
+        print('List of available languages (1):\neng', file=sys.stderr)
+        sys.exit(0)
+    elif sys.argv[-1] == 'hocr':
+        print("Image too large: (33830, 14959)\n"
+              "Error during processing.", file=sys.stderr)
+        sys.exit(1)
+    elif sys.argv[-1] == 'pdf':
+        print("Image too large: (33830, 14959)\n"
+              "Error during processing.", file=sys.stderr)
+        sys.exit(1)
+    elif sys.argv[-1] == 'stdout':
+        print("Image too large: (33830, 14959)\n"
+              "Error during processing.", file=sys.stderr)
+        sys.exit(1)
+    else:
+        print("Spoof doesn't understand arguments", file=sys.stderr)
+        print(sys.argv, file=sys.stderr)
+        sys.exit(1)
+
+    sys.exit(0)
+
+
+if __name__ == '__main__':
+    main()

tests/spoof/tesseract_cache.py

@@ -90,6 +90,13 @@ def main():
             universal_newlines=True)
     stdout, stderr = p.communicate()
 
+    if p.returncode != 0:
+        # Do not cache errors or crashes
+        print("Tesseract error", file=sys.stderr)
+        print(stdout, end='')
+        print(stderr, end='', file=sys.stderr)
+        return p.returncode
+
     with open(cache_name + '.stdout', 'w') as f:
         f.write(stdout)
     with open(cache_name + '.stderr', 'w') as f:

tests/test_main.py

@@ -113,6 +113,11 @@ def spoof_tesseract_crash():
     return spoof('tesseract', 'tesseract_crash.py')
 
 
+@pytest.fixture
+def spoof_tesseract_big_image_error():
+    return spoof('tesseract', 'tesseract_big_image_error.py')
+
+
 def test_quick(spoof_tesseract_noop):
     check_ocrmypdf('c02-22.pdf', 'test_quick.pdf', env=spoof_tesseract_noop)
 
@@ -477,3 +482,13 @@ def test_tesseract_crash_autorotate(spoof_tesseract_crash):
     assert sh.returncode == ExitCode.child_process_error
     assert not os.path.exists(_outfile('wontwork.pdf'))
     assert "ERROR" in err
+
+
+@pytest.mark.parametrize('renderer', [
+    'hocr',
+    'tesseract',
+    ])
+def test_tesseract_image_too_big(renderer, spoof_tesseract_big_image_error):
+    check_ocrmypdf(
+        'hugemono.pdf', 'hugemono_%s.pdf' % renderer, '-r',
+        '--pdf-renderer', renderer, env=spoof_tesseract_big_image_error)