Downloaded EPUB files are partially corrupted

[jzkmath]

Describe the bug
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After version 48, downloaded EPUB files have errors that prevent them from being processed by Google Play Books. Newly uploaded books will sit on the "processing" phase for an extended time period and then ultimately fail.
Workaround currently is to use calibre to convert to MOBI and then convert back to EPUB to fix corruption

Expected behavior
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Downloaded EPUB files using jncep should process fine when uploaded to google play books.

To Reproduce
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use jncep to download an epub file such as Demon Lord, retry Volume 9 part 2. Attempt to upload this epub to google play books.

Debug trace
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N/A

Running an epub checker I get the following information:

epubcheck Demon_Lord_Retry_Volume_9_Part_2.epub 
Validating using EPUB version 3.2 rules.
ERROR(OPF-029): Demon_Lord_Retry_Volume_9_Part_2.epub(-1,-1): The file "EPUB/i_cdn_j_novel_club_pub_img_1200_webp_01J_A_B_3681VEX0ECHF4280GB14B.jpg" does not appear to match the media type image/jpeg, as specified in the OPF file.
ERROR(PKG-021): Demon_Lord_Retry_Volume_9_Part_2.epub/EPUB/i_cdn_j_novel_club_pub_img_1200_webp_01J_A_B_3681VEX0ECHF4280GB14B.jpg(-1,-1): Corrupted image file encountered.
ERROR(OPF-029): Demon_Lord_Retry_Volume_9_Part_2.epub(-1,-1): The file "EPUB/i_cdn_j_novel_club_pub_img_1200_webp_01J_A_B_3770C0N8B6RK4EPPCP9AC.jpg" does not appear to match the media type image/jpeg, as specified in the OPF file.
ERROR(PKG-021): Demon_Lord_Retry_Volume_9_Part_2.epub/EPUB/i_cdn_j_novel_club_pub_img_1200_webp_01J_A_B_3770C0N8B6RK4EPPCP9AC.jpg(-1,-1): Corrupted image file encountered.
ERROR(OPF-029): Demon_Lord_Retry_Volume_9_Part_2.epub(-1,-1): The file "EPUB/i_cdn_j_novel_club_pub_img_1200_webp_01J_A_B_380PX4S5ZZYXRCPB7ZKEM.jpg" does not appear to match the media type image/jpeg, as specified in the OPF file.
ERROR(PKG-021): Demon_Lord_Retry_Volume_9_Part_2.epub/EPUB/i_cdn_j_novel_club_pub_img_1200_webp_01J_A_B_380PX4S5ZZYXRCPB7ZKEM.jpg(-1,-1): Corrupted image file encountered.

Check finished with errors
Messages: 0 fatals / 6 errors / 0 warnings / 0 infos

EPUBCheck completed

Given this information, I am guessing that jncep is generating epub files that use WEBP instead of JPG or PNG which is breaking the epub file.

Environment (please complete the following information):

• OS: Linux Mint 22
• Python version: 3.12
• JNCEP version: V48

[gvellut]

Thank you for the bug report.

I think you are right: The image has a .jpg extension but is now actually webp (like with https://cdn.j-novel.club/pub/img/1200/webp/01J/A/D/21WRCKSKBFEVTGR3GCF43.jpg). So I think there will be a need to perform a conversion (it seems my kobo cannot display them and it's possibly the same for other devices).

[gvellut]

There is a link to some doc about the image URLs #54 (comment)
It seems one can use a crafted URL to get the image in JPEG format instead of Webp: for example, for the URL above:

Webp (inside the original content):
https://cdn.j-novel.club/pub/img/1200/webp/01J/A/D/21WRCKSKBFEVTGR3GCF43.jpg

JPEG (by slightly changing the URL):
https://cdn.j-novel.club/pub/img/1200/jpg/01J/A/D/21WRCKSKBFEVTGR3GCF43.jpg

[gvellut]

Version 49 (just released) should fix the issue. Let me know if not the case.
Commit: 043a045