edgeplus

• added new threshold: EdgePlus (ScanTailor-Advanced/scantailor-advanced#48)

threshold

• threshold method: DjVuL, BiMod, Sauvola, Blur

warning

• fix warning by @plzombie (see ImageProcessing-ElectronicPublications/mfbdjvu#4 (comment))

ground

• update DjVuL: fix DjVuL ground: define mean bg and fg
• main DjVuL no changes

mask

• also use exist mask

first

• first release

CCITT Group 4 + JPEG.