Disappearing images (png converted to jpg)

Liudprand · 10-04-2022, 07:35 PM

I have quite a few books that are very large - in the hundreds of mb, in some cases.

I've worked out how to use ImageMagick to convert the png files (which are nearly always - perhaps always - used in the books in question, rather than jpegs) into jpg format, and then delete the png files from the book, and finally import the jpg files into the book.

Trouble is, although all of the new jpg image files appear in the Calibre editor exactly where the old png files did, when I open up the book they're all (apart from the cover image) completely blank - just showing "img" at the top.

Do I have to somehow re-link each image with its location within the book? If so, how... ?

Liudprand · 10-04-2022, 07:36 PM

(Just to be clear, the reason I'm converting them to jpg is that Calibre seems to be able to compress them much more easily and quickly, as opposed to png files.)

jhowell · 10-04-2022, 08:54 PM

The calibre editor has a "Replace image with file" function that can replace an image and link the new one into the book properly.

Liudprand · 10-04-2022, 09:39 PM

Quote:

Originally Posted by jhowell

The calibre editor has a "Replace image with file" function that can replace an image and link the new one into the book properly.

Right. But if there are tons of images in a book (which is usually the case, for obvious reasons, in the books I'm talking about), is there a way to replace the images other than doing it one by one?

DNSB · 10-04-2022, 09:42 PM

Quote:

Originally Posted by Liudprand

Right. But if there are tons of images in a book (which is usually the case, for obvious reasons, in the books I'm talking about), is there a way to replace the images other than doing it one by one?

You could replace the image files and then do a search replace on .png and replace it with .jpg in the html files.

This does require replacing all .png file with their .jpg version.

Karellen · 10-04-2022, 10:01 PM

Quote:

Originally Posted by Liudprand

Trouble is, although all of the new jpg image files appear in the Calibre editor exactly where the old png files did, when I open up the book they're all (apart from the cover image) completely blank - just showing "img" at the top.

Do I have to somehow re-link each image with its location within the book? If so, how... ?

Yes, you have to relink each image you replace. See the screenshot below.
For each image you replace, you need to find the corresponding link in the html files and adjust the filename so it points to the new image.

If you had used the "replace image with file..." option from the context menu on the image file, this would have happened automatically, but if the image size is different, and you specified width and height (as shown in the screenshot), then that would need to be changed manually.

Is there a way to batch change files? Not that I am aware of.

kovidgoyal · 10-04-2022, 11:30 PM

Bulk rename all the files to .jpg using the bulk rename tool in the editor. That will update all the links. Then use your scsript to actually convert the files to real jpg.

Liudprand · 10-05-2022, 09:54 AM

Quote:

Originally Posted by kovidgoyal

Bulk rename all the files to .jpg using the bulk rename tool in the editor. That will update all the links. Then use your scsript to actually convert the files to real jpg.

Thanks very much for this.

I did as you suggested, but I still have blank spaces in the book where all of the images should be.

Liudprand · 10-05-2022, 10:05 AM

Quote:

Originally Posted by Liudprand

Thanks very much for this.

I did as you suggested, but I still have blank spaces in the book where all of the images should be.

Actually, ignore that! I tried again and it worked perfectly. Must have missed something out the first time... Thanks again.

Liudprand · 10-05-2022, 11:06 AM

Actually, one follow-up question - which I realise might be asking too much!

Some of the books I have contain literally hundreds of images, some of which are already in jpg form, distributed apparently randomly throughout.

This makes it very difficult to select just the non-jpg images, other than manually. If I accidentally include just one jpg image when I'm trying to change the file extensions in bulk, it gives me an error message because, in that one case, I'm making a request that is circular. So, is there a way to sort the images in the left-hand panel by type, rather than in terms of their position in the book? Then it would be relatively easy to select just the non-jpg images.

Thanks again!

kovidgoyal · 10-05-2022, 01:01 PM

No there is no way to sort the file browser

theducks · 10-05-2022, 03:00 PM

DANGER backup

REGEX the OPF section

10-04-2022, 07:35 PM	#1
Liudprand Zealot Posts: 133 Karma: 10 Join Date: Nov 2021 Device: Kobo Libra 2	Disappearing images (png converted to jpg) I have quite a few books that are very large - in the hundreds of mb, in some cases. I've worked out how to use ImageMagick to convert the png files (which are nearly always - perhaps always - used in the books in question, rather than jpegs) into jpg format, and then delete the png files from the book, and finally import the jpg files into the book. Trouble is, although all of the new jpg image files appear in the Calibre editor exactly where the old png files did, when I open up the book they're all (apart from the cover image) completely blank - just showing "img" at the top. Do I have to somehow re-link each image with its location within the book? If so, how... ?

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10-04-2022, 07:36 PM	#2
Liudprand Zealot Posts: 133 Karma: 10 Join Date: Nov 2021 Device: Kobo Libra 2	(Just to be clear, the reason I'm converting them to jpg is that Calibre seems to be able to compress them much more easily and quickly, as opposed to png files.)

10-04-2022, 08:54 PM	#3
jhowell Grand Sorcerer Posts: 7,068 Karma: 91577715 Join Date: Nov 2011 Location: Charlottesville, VA Device: Kindles	The calibre editor has a "Replace image with file" function that can replace an image and link the new one into the book properly.

10-04-2022, 11:30 PM	#7
kovidgoyal creator of calibre Posts: 45,339 Karma: 27182818 Join Date: Oct 2006 Location: Mumbai, India Device: Various	Bulk rename all the files to .jpg using the bulk rename tool in the editor. That will update all the links. Then use your scsript to actually convert the files to real jpg.

10-05-2022, 11:06 AM	#10
Liudprand Zealot Posts: 133 Karma: 10 Join Date: Nov 2021 Device: Kobo Libra 2	Actually, one follow-up question - which I realise might be asking too much! Some of the books I have contain literally hundreds of images, some of which are already in jpg form, distributed apparently randomly throughout. This makes it very difficult to select just the non-jpg images, other than manually. If I accidentally include just one jpg image when I'm trying to change the file extensions in bulk, it gives me an error message because, in that one case, I'm making a request that is circular. So, is there a way to sort the images in the left-hand panel by type, rather than in terms of their position in the book? Then it would be relatively easy to select just the non-jpg images. Thanks again!

10-05-2022, 01:01 PM	#11
kovidgoyal creator of calibre Posts: 45,339 Karma: 27182818 Join Date: Oct 2006 Location: Mumbai, India Device: Various	No there is no way to sort the file browser

10-05-2022, 03:00 PM	#12
theducks Well trained by Cats Posts: 31,046 Karma: 60358908 Join Date: Aug 2009 Location: The Central Coast of California Device: Kobo Libra2,Kobo Aura2v1, K4NT(Fixed: New Bat.), Galaxy Tab A	DANGER backup REGEX the OPF section

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