Convert deskew to use degrees, since all our other angles are in degrees

src/ocrmypdf/_exec/tesseract.py

@@ -10,6 +10,7 @@
 import logging
 import re
 from distutils.version import StrictVersion
+from math import pi
 from os import fspath
 from pathlib import Path
 from subprocess import PIPE, STDOUT, CalledProcessError, TimeoutExpired
@@ -172,7 +173,7 @@ def get_orientation(
 def get_deskew(
     input_file: Path, languages: List[str], engine_mode: Optional[int], timeout: float
 ) -> float:
-    """Gets angle to deskew this page, in radians."""
+    """Gets angle to deskew this page, in degrees."""
     args_tesseract = tess_base_args(languages, engine_mode) + [
         '--psm',
         '2',
@@ -193,8 +194,9 @@ def get_deskew(
         raise SubprocessOutputError() from e
 
     parsed = _parse_tesseract_output(p.stdout)
-    deskew = float(parsed.get('Deskew angle', 0))
-    return deskew
+    deskew_radians = float(parsed.get('Deskew angle', 0))
+    deskew_degrees = 180 / pi * deskew_radians
+    return deskew_degrees
 
 
 def tesseract_log_output(stream):

src/ocrmypdf/_pipeline.py

@@ -6,7 +6,6 @@
 
 
 import logging
-import math
 import os
 import re
 import sys
@@ -479,9 +478,7 @@ def preprocess_deskew(input_file: Path, page_context: PageContext):
     dpi = get_page_square_dpi(page_context.pageinfo, page_context.options)
 
     ocr_engine = page_context.plugin_manager.hook.get_ocr_engine()
-    deskew_angle = ocr_engine.get_deskew(input_file, page_context.options)
-
-    deskew_angle_degrees = deskew_angle * 180.0 / math.pi
+    deskew_angle_degrees = ocr_engine.get_deskew(input_file, page_context.options)
 
     with Image.open(input_file) as im:
         # According to Pillow docs, .rotate() will automatically use Image.NEAREST

src/ocrmypdf/pluginspec.py

@@ -368,7 +368,7 @@ class OcrEngine(ABC):
 
     @staticmethod
     def get_deskew(input_file: Path, options: Namespace) -> float:
-        """Returns the deskew angle of the image, in radians."""
+        """Returns the deskew angle of the image, in degrees."""
         return 0.0
 
     @staticmethod

tests/test_preprocessing.py

@@ -5,7 +5,7 @@
 # file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
 
-from math import isclose, pi
+from math import isclose
 
 import pytest
 from PIL import Image
@@ -36,7 +36,7 @@ def test_deskew(resources, outdir):
         pageno=1,
     )
 
-    skew_angle = tesseract.get_deskew(deskewed_png, [], None, 5.0) * 180 / pi
+    skew_angle = tesseract.get_deskew(deskewed_png, [], None, 5.0)
     print(skew_angle)
     assert -0.5 < skew_angle < 0.5, "Deskewing failed"