GuetzliImageIOPlugin
Version: GIT Web: www.bit.ly/2CCxbBg
Under this hard-to-read word we can find a Qt image plugin, which delivers the Guetzli JPEG encoder in the form of Qt image plugin. We already wrote about Guetzli (‘a cookie’ in Swiss German) in LXF224, and admitted that this small piece of software developed by Google turned out to be very effective in further slimming down JPEG files. Guetzli is a perceptual encoder that produces nonprogressive JPEGs that are typically 20-30% smaller than ‘normal’ JPEGs (assuming you used libjpeg to get them). This dedicated image plugin for Guetzli is a great addition to the boring command line tool of Guetzli itself, as it opens the door for dozens of Qt-based imaging apps to write and read files generated by Guetzli. The plugin is a shared library that you should put in a place like /usr/lib64/qt5/plugins/ imageformats – check your distribution’s default prefix for image plugins if that path is empty on your system, of course.
After you’ve installed it, GuetzliImageIOPlugin doesn’t supersede standard Qt image library for reading JPEG files in common applications: instead it provides an API for developing custom Qt-based image encoders and viewers that would benefit from Guetzli. The source package of the plugin already comes with a demo app called
SimpleGuetzliGUI and showcases the work of the plugin. With this app, you can open an existing JPEG or PNG file, and re-encode it to Guetzli-style JPEG. The GUI shows image size figures for both source and target files and has just two buttons: Open and Save As. Guetzli delivers the best compression gain if you set the quality ratio to something around 85%, and it’s very easy to prove that with SimpleGuetzliGUI.
We highly recommend using this image plugin for showing the benefits of the new JPEG encoder – and for escaping the command line in favour of userfriendly imaging applications.
“Custom Qt-based image encoders and viewers that would benefit from Guetzli”