Add tesseract caching to speed up tests

tests/spoof/tesseract_cache.py

@@ -0,0 +1,73 @@
+#!/usr/bin/env python3
+import sys
+import os
+import hashlib
+import shutil
+import subprocess
+
+
+CACHE_PATH = os.path.abspath(os.path.join(
+        os.path.dirname(__file__), '..', 'cache'))
+
+
+def main():
+    operation = sys.argv[-1]
+    # For anything except a hocr or pdf, defer to real tesseract
+    if operation != 'hocr' and operation != 'pdf':
+        tess_args = ['tesseract'] + sys.argv[1:]
+        os.execvp("tesseract", tess_args)
+        return  # Not reachable
+
+    try:
+        os.makedirs(CACHE_PATH)
+    except FileExistsError:
+        pass
+
+    m = hashlib.sha1()
+
+    version = subprocess.check_output(
+        ['tesseract', '--version'],
+        stderr=subprocess.STDOUT)
+
+    m.update(version.encode())
+    m.update(operation.encode())
+
+    try:
+        lang = sys.argv[sys.argv.index('-l') + 1]
+        m.update(lang.encode())
+    except ValueError:
+        pass
+
+    input_file = sys.argv[-3]
+    output_file = sys.argv[-2]
+
+    if operation == 'hocr':
+        output_file += '.hocr'
+    elif operation == 'pdf':
+        output_file += '.pdf'
+
+    with open(input_file, 'rb') as f:
+        m.update(f.read())
+
+    cache_name = os.path.join(CACHE_PATH, m.hexdigest())
+    if os.path.exists(cache_name):
+        # Cache hit
+        print("Tesseract cache hit", file=sys.stderr)
+        shutil.copy(cache_name, output_file)
+        sys.exit(0)
+
+    # Cache miss
+    print("Tesseract cache miss", file=sys.stderr)
+
+    # Call tesseract
+    subprocess.check_call(['tesseract'] + sys.argv[1:])
+
+    # Insert file into cache
+    if os.path.exists(output_file):
+        shutil.copy(output_file, cache_name)
+    else:
+        print("Could not find output file", file=sys.stderr)
+
+
+if __name__ == '__main__':
+    main()