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From: "ibrahim via 9fans" <9fans@9fans.net>
To: 9fans <9fans@9fans.net>
Subject: Re: [9fans] licence question
Date: Sat, 29 Jan 2022 17:40:32 -0500	[thread overview]
Message-ID: <16434960320.29d60.470765@composer.9fans.topicbox.com> (raw)
In-Reply-To: <AAD18109-9CCD-42FB-8509-56E33BA8509D@iitbombay.org>

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On Saturday, 29 January 2022, at 11:14 PM, Bakul Shah wrote:
> Note that djvu would compress things very nicely. A full page
300dpi magazine color page that may be 25MB uncompressed will
compress down to 40K-80K or so and be very legible, much more
so compared a similar sized jpeg compressed image.

Thanks for your hint. I'm using djvu format for scanned book pages for my private use. The algorithm isn't easy to reimplement cause it uses pattern matching in an extensive way. You get the best results for scanned material where as an example letters are matched quite often. It has superb compression ratios but is slow regarding decompression or rendering.

Regarding handwritten scans the best method I experienced is edge detection filtering and color indexing to create a ppm image. Compression leads than to smaller sizes than by using jpeg. Decompression is faster and when you combine two lines to single one (subpixeling) you get smooth and clean images.

For printed sources djvu produces far smaller results. Thank you for this hint.

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  reply	other threads:[~2022-01-29 22:40 UTC|newest]

Thread overview: 61+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-01-27 22:43 ibrahim via 9fans
2022-01-27 22:48 ` hiro
2022-01-27 23:33   ` ibrahim via 9fans
2022-01-28  0:05     ` hiro
2022-01-28  0:42       ` ibrahim via 9fans
2022-01-28  0:46         ` ori
2022-01-28  1:14           ` ibrahim via 9fans
2022-01-28  3:23             ` Kurt H Maier via 9fans
2022-01-28 12:01               ` ibrahim via 9fans
2022-01-28 21:59                 ` hiro
2022-01-29 13:03                   ` ibrahim via 9fans
2022-01-29 13:24                     ` hiro
2022-01-29 14:08                       ` ibrahim via 9fans
2022-01-29 14:59                         ` sirjofri
2022-01-29 18:11                         ` Grant Defayette
2022-01-29 19:00                           ` ibrahim via 9fans
2022-01-29 20:43                         ` hiro
2022-01-29 21:32                           ` ibrahim via 9fans
2022-01-29 21:42                             ` hiro
2022-01-29 22:23                               ` ibrahim via 9fans
2022-01-29 23:14                                 ` sirjofri
2022-01-29 23:27                                   ` hiro
2022-01-29 23:36                                   ` ibrahim via 9fans
2022-01-30  0:08                                     ` hiro
2022-01-30  1:45                                       ` ron minnich
2022-01-30  2:18                                         ` ibrahim via 9fans
2022-01-30 21:00                                           ` ron minnich
2022-02-01 15:08                                             ` ibrahim via 9fans
2022-02-01 17:06                                               ` Dan Cross
2022-01-29 22:14                         ` Bakul Shah
2022-01-29 22:40                           ` ibrahim via 9fans [this message]
2022-02-04 15:30                         ` Kent R. Spillner
2022-02-04 16:17                           ` Grant Defayette
2022-02-04 16:29                           ` ibrahim via 9fans
2022-02-04 21:12                             ` sirjofri
2022-02-04 17:48                           ` Kurt H Maier via 9fans
2022-02-05  0:08                             ` Frank D. Engel, Jr.
2022-02-05 16:47                               ` hiro
2022-01-29 14:26                     ` David Leimbach via 9fans
2022-02-01 14:12                       ` Dan Cross
2022-02-01 22:47                         ` hiro
2022-02-02 13:22                           ` Wes Kussmaul
2022-02-02 16:25                             ` ori
2022-02-02 18:22                               ` ron minnich
2022-02-02 19:00                                 ` ibrahim via 9fans
2022-01-29 16:15                     ` Wes Kussmaul
2022-01-29 16:56                     ` Bakul Shah
2022-01-29 17:17                       ` ori
2022-01-29 18:14                       ` ibrahim via 9fans
2022-01-29 18:58                     ` cinap_lenrek
2022-01-29 19:23                       ` ibrahim via 9fans
2022-01-29 20:48                         ` hiro
2022-01-29 21:18                           ` Steve Simon
2022-01-29 21:34                             ` hiro
2022-01-29 21:43                             ` ibrahim via 9fans
2022-01-29 22:44                               ` hiro
2022-01-29 23:26                                 ` ibrahim via 9fans
2022-01-30  7:55                           ` tlaronde
2022-01-30 13:44                             ` ibrahim via 9fans
2022-01-30 13:56                               ` tlaronde
2022-01-28  3:14 ` Lucio De Re

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