Download PDF books from archive.org

Internet Archive (archive.org) holds more than 34 millions books. Some books are permitted to read online by borrowing for a limit period. With the extension, the borrowed books can be downloaded for offline reading.
HathiTrust Digital Library (hathitrust.org) support added. All books with full view permission can be downloaded.

Usage
For Internet Archive (https://archive.org/):
After borrowing a book, two new buttons, ""Quality"" and ""Download"", appear under the book viewer alongside the ""Favorite"" button.

To get the current book as a PDF file, press the ""Download"" button.
To get each leaf as a JPEG file, press the ""Download"" button while holding Ctrl key (Command key on Mac).
To get only a range of leafs, press the ""Download"" button while holding Alt key (Option key on Mac), then input a range.

For HathiTrust (https://hathitrust.org/):
For books with full view permission, a new section, ""Ayesha"", appears above the ""Download"" section on the left-hand side of the page. The section contains three buttons, ""Quality"", ""Tasks"" and ""Download"".

To get the current book as a PDF file, press the ""Download"" button.
To get each leaf as a JPEG/PNG file, press the ""Download"" button while holding Ctrl key (Command key on Mac).
To get only a range of leafs, press the ""Download"" button while holding Alt key (Option key on Mac), then input a range.

The download process may take some breaks due to server constraints.

Availability
For Brave below version 1.67.119, item 'File System Access API' on 'brave://flags' page should be enabled.

Change log
v0.7.3
* Bug fix and improvement of leaf range selection function

v0.7.2
* Add Leaf range selection support
* On range download, the range number was appended to the default downloaded filename

v0.7.0
* Add hathitrust.org support
* Add PNG leaf type support
* Add HTTP 502/504 gateway errors support, when that happened download will retry, not just abort
* If the buttons does not appear due to slow network, you can show it manually by clicking the extension icon on the browser toolbar after the page being loaded

v0.6.3
* Possible download succeeded with 0 byte PDF file for large books. Now fixed

v0.6.2
* Quality code was appended to the default downloaded filename
* Books will be returned automatically on successful download for availablity to other users

v0.6.1
* Possibble leaf lost caused by unexpected abort. Now fixed
* In some browsers under incorrect settings, download succeeded but no PDF file found. Now fixed
* For Brave, whenever the browser is launched, the extension have to be refreshed. Now fixed

v0.6.0
* Downloads will now retry automatically on network errors. So it will work more smoothly than ever
* Download process can be aborted at any time. There is no need to wait for cleaning up any more
* Inaccurate button title place. Now fixed
* More browsers are supported
* Compatibility improvements

v0.5.0
* Add option of download as JPEG files

v0.4.0
* Retrieve the leaf info from book structure instead of from book view page, in case it may be incorrect on boundary conditions
* Add metadata to the PDF file
* Add button title with the same style as the page
* The buttons show up quickly even on slow network now
* Improve the reliability and stability

v0.3.0
* Add option of leaf quality
* Constraint the download function to the books that can be borrowed, don't interfere with the books of always available
* Clean uncompleted files on failed/canceled downloads

v0.2.0
* Download to a whole PDF book
* Independant of CORS extension

v0.1.0
* Download each leaf to a single JPEG file
* Dependant on CORS extension"