New module RenderImage (alongside existing RenderText) to provides
image rendering and scaling facilities.
Uses MuPDF, but tries first giflib on GIF.
Allows for getting all the frames from an animated GIF.
This adds a button to the Tap Plus menu, that allows
extracting metadata and cover images for books in
current directory. Info about the process and questions are
initially shown and asked, and the process can be aborted at
any moment.
bump crengine:
Allow for quicker loading when interested in metadata only.
Allow for more than 65535 different attribute values.
Increase gamma values range.
Remove the subprocess management functions from xutil.lua, as they were
moved into base/ffi/util.lua, and use them from there.
Also use the cre_storage_size_factor setting when processing credocuments,
to avoid CRE WARNING while indexing too.
Fix dealing with MuPDF document opening failures (previously, these
were not noticed and indexing was retried each time).
cre:loadDocument() may fail in recognizing the document format, and
koreader would previously keep calling other methods on it, which would
make crengine segfaults. We now check loadDocument success at the
various places it is called, and try to deal the best way we can when it fails.
We previously disabled cache, but that may cause excessive
memory usage with big books. We now use a temporary
cache directory, that we clean when no more needed.
So an image file can have a cover in coverbrowser's display.
It also allows for an alternative viewer (ImageViewer widget)
when holding on file / View full size cover.
* CoverBrowser plugin: alt views for File Browser and History
* Added Prune cache and Compact cache menu actions
* Support for book descriptions, and settings stored in db
