v13 release notes

docs/release_notes.rst

@@ -17,6 +17,36 @@ wish to use some of its features for working with PDFs.
    Python 3.6 reaches end of life on December 23, 2021. We will continue to support
    OCRmyPDF v12.x if major issues are identified until that date.
 
+v13.0.0
+=======
+
+**Breaking changes**
+
+-  The deprecated module ``ocrmypdf.leptonica`` has been removed.
+-  We no longer depend on Leptonica (``liblept``) or CFFI.
+-  The argument ``--remove-background`` is temporarily disabled while we search for an
+   alternative to the Leptonica implementation of this feature.
+-  The ``--threshold`` argument has been removed, since this also depended on Leptonica.
+   Tesseract 5.x has implemented improvements to thresholding, so this feature will be
+   redundant anyway.
+-  ``--deskew`` was previous calculated by a Leptonica algorithm. We now use a feature
+   of Tesseract to term the appropriate the angle to deskew a page. The deskew angle
+   according to Tesseract may differ from Leptonica's algorithm. At least in theory,
+   Tesseract's deskew angle is informed by a more complex analysis than Leptonica,
+   so this should improve results in general. We also use Pillow to perform the
+   deskewing, which may affect the appearance of the image compared to Leptonica.
+-  Support for Python 3.6 was dropped along with shims needed to support.
+-  We now require pikepdf 4.0 or newer. This, in turn, means that OCRmyPDF requires
+   a system compatible with the manylinux2014 specification. This change was "forced"
+   by Pillow not releasing manylinux2010 wheels anymore.
+
+**Fixes**
+
+-  Fixed an issue where OCRmyPDF failed to find Ghostscript on Windows even when 
+   installed, and would exit with an error.
+-  By removing Leptonica, we fixed all issues related to Leptonica on Apple
+   Silicon or Leptonica failing to import on Windows.
+
 v12.7.2
 =======