Which JPEG compresion algorithms in ebook editor?

Francois_C · 04-09-2017, 06:47 AM

I love the ebook editor and I use it daily, but, just out of curiosity I would like to know which algorithms are used in JPEG lossless compression of covers and images.

I get better results (about 6%) with it than with Timo Kokkonen's jpegoptim, which strips metadata and optimizes Huffman tables for lossless compression.

Are you using wavelet compression? I heard about applying some sort of JP2000 algorithm on JPEG files.

JSWolf · 04-09-2017, 06:48 AM

The editor's compression also removes the crud from graphics and optimizes them.

kovidgoyal · 04-09-2017, 07:55 AM

mozjpeg is used for jpeg compression.

Francois_C · 04-09-2017, 08:17 AM

Thank you, Kovid and JSWolf.
So, I'll have a look to mozjpeg. I had forgotten to change DCT to progressive with jpegoptim, (as Calibre does), but Calibre/mozjpeg is still 1% better.

04-09-2017, 06:47 AM	#1
Francois_C Zealot Posts: 106 Karma: 8300 Join Date: Jul 2012 Location: France Device: Kobo Aura H2O, Kobo Touch, Kobo Mini	Which JPEG compresion algorithms in ebook editor? I love the ebook editor and I use it daily, but, just out of curiosity I would like to know which algorithms are used in JPEG lossless compression of covers and images. I get better results (about 6%) with it than with Timo Kokkonen's jpegoptim, which strips metadata and optimizes Huffman tables for lossless compression. Are you using wavelet compression? I heard about applying some sort of JP2000 algorithm on JPEG files. Last edited by Francois_C; 04-09-2017 at 06:55 AM.

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04-09-2017, 06:48 AM	#2
JSWolf Resident Curmudgeon Posts: 73,957 Karma: 128903250 Join Date: Nov 2006 Location: Roslindale, Massachusetts Device: Kobo Libra 2, Kobo Aura H2O, PRS-650, PRS-T1, nook STR, PW3	The editor's compression also removes the crud from graphics and optimizes them.

04-09-2017, 07:55 AM	#3
kovidgoyal creator of calibre Posts: 43,850 Karma: 22666666 Join Date: Oct 2006 Location: Mumbai, India Device: Various	mozjpeg is used for jpeg compression.

04-09-2017, 08:17 AM	#4
Francois_C Zealot Posts: 106 Karma: 8300 Join Date: Jul 2012 Location: France Device: Kobo Aura H2O, Kobo Touch, Kobo Mini	Thank you, Kovid and JSWolf. So, I'll have a look to mozjpeg. I had forgotten to change DCT to progressive with jpegoptim, (as Calibre does), but Calibre/mozjpeg is still 1% better.