Calibre dont like 256 colors png cover

un_pogaz · 07-10-2018, 11:15 AM

To reduce the size of my EPUB, I use Riot for optimize the picture of the book, especialy the cover.

I know that when integrating metadata Caliber my also updated the cover.
For JPG, okay.
But sometimes, a PNG cover, in 256 colors is more optimal without loss of quality (example with the attached image: Black and white, without or little gradation)
I optimize my image, put it manually in the book, then I update my metadata as well as the recorded size.
And I see that the size hasn't changed:
=> Caliber has reset the cover to TrueColors

(In the example image, the size increases from 226 KB to 95 KB)

kovidgoyal · 07-10-2018, 12:18 PM

calibre stores covers in JPG format. JPG does not support indexed images. If you want to preserve the cover in your EPUB files you can either:

1) Turn off theEPUB metadata writer plugin in calibre, then EPUB metadata including covers will not be changed

2) Do not set a cover for the boo in calibre, then the in-book cover will be preserved

un_pogaz · 07-11-2018, 03:15 AM

Quote:

Originally Posted by kovidgoyal

calibre stores covers in JPG format. JPG does not support indexed images. If you want to preserve the cover in your EPUB files you can either:

1) Turn off theEPUB metadata writer plugin in calibre, then EPUB metadata including covers will not be changed

2) Do not set a cover for the boo in calibre, then the in-book cover will be preserved

1) I found something "Set EPUB metadata / Personalization : disable-add-missing-cover" but I don't think that's it.

2) What ???

Would it be possible to diversify the button "Integrated metadata" by adding 2 options ;
1) Integrated metadata without cover
2) Integrated the cover

For now, he does both at the same time and without distinction, which I find very foolish.
Added a separated function would resolve my problem easily, and would add finesse to Calibre.

kovidgoyal · 07-11-2018, 03:33 AM

1) Disable the plugin entirely
or
2) Delete the cover from calibre, then calibre will not update the cover in the book

I'm afraid I'm not interested in adding a setting to only update non-cover metadata.

un_pogaz · 07-11-2018, 06:04 AM

Delete the cover from calibre => Delete cover.jpg => No preview
...
I do not call that a solution.
The problem is avoided in an ugly and inelegant way.
Sure, with his methods: no need to solve a problem, there is not, since we all will do everything not to be confronted with it *whistle*.
*sigh*

By the way,
Thank for the answer and for taking the time to explain to me.

Divingduck · 07-11-2018, 02:24 PM

Take a look to the plugin section. There you will find the PI ModifyEPUB.

un_pogaz · 07-12-2018, 02:43 AM

Quote:

Originally Posted by Divingduck

Take a look to the plugin section. There you will find the PI ModifyEPUB.

Thank o/

07-10-2018, 11:15 AM	#1
un_pogaz Chalut o/ Posts: 410 Karma: 145324 Join Date: Dec 2017 Device: Kobo	Calibre dont like 256 colors png cover To reduce the size of my EPUB, I use Riot for optimize the picture of the book, especialy the cover. I know that when integrating metadata Caliber my also updated the cover. For JPG, okay. But sometimes, a PNG cover, in 256 colors is more optimal without loss of quality (example with the attached image: Black and white, without or little gradation) I optimize my image, put it manually in the book, then I update my metadata as well as the recorded size. And I see that the size hasn't changed: => Caliber has reset the cover to TrueColors (In the example image, the size increases from 226 KB to 95 KB) Attached Thumbnails

07-11-2018, 02:24 PM	#6
Divingduck Wizard Posts: 1,161 Karma: 1404241 Join Date: Nov 2010 Location: Germany Device: Sony PRS-650	Take a look to the plugin section. There you will find the PI ModifyEPUB. Attached Thumbnails

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
translating calibre: strings I dont understand	trijntje	Development	7	08-21-2011 07:02 AM
Calibre dont detect sony prs 500 ubuntu 10.10	pery_soy	Devices	6	04-25-2011 02:50 PM
How to save the book cover in png	georgen	Calibre	13	02-18-2011 03:49 PM
PRS-600 ADE ans Calibre dont recignize	Wesley	Sony Reader	1	12-08-2009 08:29 PM
where to get autorun.xml, icon.png, key.png, lut.bin for PRS-505	obender	Sony Reader Dev Corner	2	01-25-2009 03:20 PM

07-10-2018, 12:18 PM	#2
kovidgoyal creator of calibre Posts: 43,842 Karma: 22666666 Join Date: Oct 2006 Location: Mumbai, India Device: Various	calibre stores covers in JPG format. JPG does not support indexed images. If you want to preserve the cover in your EPUB files you can either: 1) Turn off theEPUB metadata writer plugin in calibre, then EPUB metadata including covers will not be changed 2) Do not set a cover for the boo in calibre, then the in-book cover will be preserved

07-11-2018, 03:33 AM	#4
kovidgoyal creator of calibre Posts: 43,842 Karma: 22666666 Join Date: Oct 2006 Location: Mumbai, India Device: Various	1) Disable the plugin entirely or 2) Delete the cover from calibre, then calibre will not update the cover in the book I'm afraid I'm not interested in adding a setting to only update non-cover metadata.

07-11-2018, 06:04 AM	#5
un_pogaz Chalut o/ Posts: 410 Karma: 145324 Join Date: Dec 2017 Device: Kobo	Delete the cover from calibre => Delete cover.jpg => No preview ... I do not call that a solution. The problem is avoided in an ugly and inelegant way. Sure, with his methods: no need to solve a problem, there is not, since we all will do everything not to be confronted with it whistle. sigh By the way, Thank for the answer and for taking the time to explain to me.