ImageProcessing gem is a wrapper around MiniMagick and ruby-vips, and
implements an interface for common image resizing and processing. This
is the canonical image processing gem recommended in [Shrine], and
that's where it developed from. The initial implementation was extracted
from Refile, which also implements on-the-fly transformations.
Some features that ImageProcessing gem adds on top of MiniMagick:
* resizing macros
- #resize_to_limit
- #resize_to_fit
- #resize_to_fill
- #resize_and_pad
* automatic orientation
* automatic thumbnail sharpening
* avoids the complex and inefficient MiniMagick::Image class
* will use "magick" instead of "convert" on ImageMagick 7
However, the biggest feature of the ImageProcessing gem is that it has
an alternative implementation that uses libvips. Libvips is an
alternative to ImageMagick that can process images very rapidly (we've
seen up 10x faster than ImageMagick).
What's great is that the ImageProcessing gem provides the same interface
for both implementations. The macros are named the same, and the libvips
implementation does auto orientation and thumbnail sharpening as well;
only the operations/options specific to ImageMagick/libvips differ. The
integration provided by this PR should work for both implementations.
The plan is to introduce the ImageProcessing backend in Rails 6.0 as the
default backend and deprecate the MiniMagick backend, then in Rails 6.1
remove the MiniMagick backend.
In this way we avoid HTML, XML, SVG and other files that can be rendered
by the browser to be served inline by default. Depending on the origin
from where these files are served, this might lead to XSS
vulnerabilities, and in the best case, to more realistic phishing
attacks and open redirects.
We force it rather than falling back to it when other disposition is not
provided. Otherwise it would be possible for someone to force inline
just by passing `disposition=inline` in the URL.
The list of content types to be served as attachments is configurable.
