docs: update to discuss some v15 features not yet documented

docs/advanced.rst

@@ -117,14 +117,14 @@ exceed a certain number of megapixels with ``--skip-big``. (A 300 DPI,
 OCR for huge images
 -------------------
 
-Separate from these settings, Tesseract has internal limits on the size
+Tesseract has internal limits on the size
 of images it will process. If you issue
 ``--tesseract-downsample-large-images``, OCRmyPDF will downsample images
 to fit Tesseract limits. (The limits are usually entered only for scanned
 images of oversized media, such as large maps or blueprints exceeding
 110 cm or 43 inches in either dimension, and at high DPI.)
 
-``--tesseract-downsample-above`` adjusts the threshold at which images
+``--tesseract-downsample-above Npixels`` adjusts the threshold at which images
 will be downsampled. By default, only images that exceed any of Tesseract's
 internal limits are downsampled.
 
@@ -195,10 +195,10 @@ In each case OCRmyPDF will search the ``PATH`` environment variable to
 locate the binaries. By modifying the ``PATH`` environment variable, you
 can override the binaries that OCRmyPDF uses.
 
-Changing tesseract configuration variables
+Changing Tesseract configuration variables
 ------------------------------------------
 
-You can override tesseract's default `control
+You can override Tesseract's default `control
 parameters <https://tesseract-ocr.github.io/tessdoc/tess3/ControlParams.html>`__
 with a configuration file.
 
@@ -273,7 +273,7 @@ Unlike ``sandwich`` this renderer is implemented within OCRmyPDF; anyone
 looking to customize how OCR is presented should look here. A major
 disadvantage of this renderer is it not capable of correctly handling
 text outside the Latin alphabet (specifically, it supports the ISO 8859-1
-character). Pull requests to improve the situation are welcome.
+character set). Pull requests to improve the situation are welcome.
 
 Currently, this renderer has the best compatibility with Mozilla's
 PDF.js viewer.
@@ -286,11 +286,31 @@ Rendering and rasterizing options
 .. versionadded:: 14.3.0
 
 The ``--continue-on-soft-render-error`` option allows OCRmyPDF to
-proceed if a page cannot be rasterized rendered. This is useful if you are
+proceed if a page cannot be rasterized/rendered. This is useful if you are
 trying to get the best possible OCR from a PDF that is not well-formed,
 and you are willing to accept some pages that may not visually match the
 input, and that may not OCR well.
 
+Color conversion strategy
+=========================
+
+.. versionadded:: 15.0.0
+
+OCRmyPDF uses Ghostscript to convert PDF to PDF/A. In some cases, this
+conversion requires color conversion. The default strategy is to convert
+using the ``LeaveColorUnchanged`` strategy, which preserves the original
+color space wherever possible (some rare color spaces might still be
+converted).
+
+Usually document scanners produce PDFs in the sRGB color space, and do
+not need to be converted, so the default strategy is appropriate.
+
+Suppose that you have a document that was prepared for professional
+printing in a Separation or CMYK color space, and text was converted to
+curves. In this case, you may want to use a different color conversion
+strategy. The ``--color-conversion-strategy`` option allows you to select a
+different strategy, such as ``RGB``.
+
 Return code policy
 ==================
 

docs/installation.rst

@@ -420,12 +420,12 @@ to change the PATH.
 
     As of early 2021, users have reported problems with the Microsoft Store version of
     Python and OCRmyPDF. These issues affect many other third party Python packages.
-    Please download Python from Python.org or Chocolatey instead, and do not use the
+    Please download Python from Python.org or a package manager instead of the
     Microsoft Store version.
 
 .. warning::
 
-    32-bit Windows might work, but is not supported.
+    32-bit Windows is not supported.
 
 Windows Subsystem for Linux
 ---------------------------
@@ -558,7 +558,7 @@ The following versions are required:
 -  unpaper 6.1
 
 We recommend 64-bit versions of all software. (32-bit versions are not
-supported, although they may still work.)
+supported, although on Linux, they may still work.)
 
 jbig2enc, pngquant, and unpaper are optional. If missing certain
 features are disabled. OCRmyPDF will discover them as soon as they are

docs/jbig2.rst

@@ -59,5 +59,9 @@ To turn on JBIG2 lossy mode, add the argument ``--jbig2-lossy``.
 also required. Also, a JBIG2 encoder must be installed as described in
 the previous section.
 
+You can adjust the threshold for JBIG2 compression with the
+``--jbig2-threshold``. The default is 0.85, meaning that if two symbols
+are 85% similar, they will be compressed together.
+
 *Due to an oversight, ocrmypdf v7.0 and v7.1 used lossy mode by
 default.*

docs/optimizer.rst

@@ -45,8 +45,8 @@ Optimizations that always occurs
 ================================
 
 OCRmyPDF will automatically replace obsolete or inferior compression schemes
-such as RLE or LZW with superior schemes such as Deflate and converting
-monochrome images to CCITT G4. Since this is harmless it always occurs and there
+such as RLE or LZW with superior schemes such as Deflate, and convert
+monochrome images to CCITT G4. Since this is lossless, it always occurs and there
 is no way to disable it. Other non-image compressed objects are compressed as
 well.