K2pdfopt 2.53 + x64

NEW FEATURES:
Added more support for DJVU input files, including OCR-layer text extraction, reading of bookmarks, and information viewing (-i or GUI "Info" view).
Added support for CBZ input files.
ENHANCEMENTS:
The multithreaded Tesseract OCR capability has been significantly improved. The images for OCR processing are now queued up into larger groups so that the multithreading is more effective. Since the introduction of the -ocrd option in v2.50 (Dec 2018), the default OCR method of OCRing an entire line of text at a time had effectively turned off OCR multithreading since only one row of text at a time was passed to the OCR engine.
Updated many of the support libraries to their latest releases:
Tesseact 4.1.1, Leptonica 1.79, Mupdf 1.17, Freetype 2.10.2 libpng 1.6.37, jpeg-turbo 2.0.4, openjpeg 2.3.1
When previewing "marked up" pages, the preview now only processes the desired preview page, making it much faster for previewing pages above page 1.
Added -ocrvbb option to more precisely determine OCR layer text bounding boxes in pre-existing OCR layers.
BUG FIXES:
Fixed bug in ocr layer sorting algorithm in wtextchars_group_by_words() function in k2ocr.c
Fixed a bug where one of my png image reading functions was notthread safe (not re-entrant). This had the potential to cause very random crashing.
Fixed multiple issues with text selection of a pre-existing OCR layer. Some text wasn't always included in certain cases, and sometimes the selection box was over-sized.
Altered the detection of words in a row of text to work better / more consistently in obvious cases. See v2.53 comments in get_word_gap_threshold() in bmpregion.c.

Fixed problem when scaling sometimes gets out of control with tall regions. Was causing excessively large bitmaps to be allocated which would sometimes run the system out of memory.