What is the most efficient procedure to generate BW images?

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kusnick

What is the most efficient procedure to generate BW images?

Post by kusnick »

Hi folks. I’ve been used XNVIEW to convert my images to binary. I use the “no dither” option and save the image in PNG format. It seems to me the way to generate the smallest file size. The “Floyd Steinberg” option generates a better 2 unique color archive, but the result with PNG file is awful (10 x larger than the “no dither option”.
So I ask you… there’s something else I can do or this is the “end of history” for now in terms of BW files?
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strider1551
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Re: What is the most efficient procedure to generate BW imag

Post by strider1551 »

So you're asking how to produce the smallest bitonal (b/w) image? I also take it you need it in an image format (png, tiff, etc.) and not a document format (pdf, djvu - although djvu is technically an image format, but anyway...)?

If you need something that is loseless (absolutely no loss in quality), last I knew the best compression method was CCITT Group4, sometimes abbreviated to just G4. It is commonly used with TIFF images. It does well enough that I never consider it worthwhile to even bother with something lossy for a bitonal image.
kusnick

Re: What is the most efficient procedure to generate BW imag

Post by kusnick »

Thanks for the hint. Yes, I’m talking about the bitonal image file and not about the document format. What matters, anyway, is the final result… and in this case I’ve used PDF because it is still the most widespread format for sharing, despite the fact I think I can get better results from DJVU.
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dingodog
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Re: What is the most efficient procedure to generate BW imag

Post by dingodog »

a specific utility for optimize conversion of colorful images in B/W is

optimize2bw
- http://www.exactcode.de/site/open_sourc ... utilities/
optimize2bw: Reads shaded, color or gray image files and does perform automatic thresholding and optional scaling on the data. It is useful for long term archiving of documents that have to be stored in sub-byte black and white data to reduce storage requirements.
included in

exactimage tools
- http://www.exactcode.de/site/open_source/exactimage/
- http://www.exactcode.de/site/open_sourc ... /releases/

generally speaking, any dithering must be avoided; more black points,mean more information, more information mean bigger size for image

for book scans, you need to CLEAN the background, in order to have a white background

*Scantailor*
is able to perform this task for you
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