I would like to get to the bottom of what I am doing wrong that leads to black and white documents having a bigger filesize than color.
My process for a color TIFF is like this:
① tiff2pdf
② ocrmypdf
③ pdf2djvu
Resulting color DjVu file is ~56k. When pdfimages -all
runs on the intermediate PDF file, it shows CCITT (fax) is inside.
My process for a black and white TIFF is the same:
① tiff2pdf
② ocrmypdf
③ pdf2djvu
Resulting black and white DjVu file is ~145k (almost 3× the color size). When pdfimages -all
runs on the intermediate PDF file, it shows a PNG file is inside. If I replace step ① with ImageMagick’s convert
, the first PDF is 10mb, but in the end the resulting djvu
file is still ~145k. And PNG is still inside the intermediate PDF.
I can get the bitonal (bilevel) image smaller by using cjb2 -clean
, which goes straight from TIFF to DjVu, but then I can’t OCR it due to the lack of PDF intermediate version. And the size is still bigger than the color doc (~68k).
#askFedi
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