imgio: your friendly image asset resizing service

Usage

imgio helps you resizing images along the lines of src.sencha.io. In short: add a prefix to an image URL, and get the image resized to whatever size you need. imgio will never size up an image though: what you'll get instead is an image matching the requested ratio.

imgio creates PNG and JPEG output files, and supports a plethora of input formats - everything RMagick handles.

When it takes a bit longer...

...to fetch the images from their respective sources, then you will be glad that @Overbyrd implemented sinatra async mode. This mode, which is the default on ruby 1.9 installations (and, btw, is not available on Ruby 1.8.7) lets your imgio instance fetch a number of images in parallel. You could do this by deploying multiple imgio instances behind an apache or nginx proxy - but this way your CPU is used more effectively (and a free Heroku instance looks much better now.)

HTML

The following <img> tag will always be 120px wide and 90px high. The requested image will be rescaled to fill that size. Overflowing parts of the image will be cut off.

<img src="http://<yourserver>/fill/120x90/http://www.google.de/images/srpr/logo3w.png" width="120" height="90">
</img>

The requested image will be rescaled to fit completely into the requested size. Empty parts are filled in white (JPEG) or transparent (PNG).

<img src="http://<yourserver>/fit/120x90/http://www.google.de/images/srpr/logo3w.png" width="120" height="90">
</img>

Things that automatically scale its content. (UIImageView, android.widget.ImageView)

Such views allow you to scale & fill properly by themselves. However, escecially on mobile platforms scaling down the image to whatever is actually needed still helps with not wasting precious memory and CPU resources. To do so, just request http://<yourserver>/fill/120x90/http://www.google.de/images/srpr/logo3w.png instead.

The full URL syntax

The URL describes an internal workflow. Think of it as a Unix shell pipe in left to right: the source URL goes in, travels through different data processors ('robots'), and finally comes out of the workflow again. The full URL syntax is http://<yourserver>/[robot[/options]]*/uri. Which and how many, if any, options are valid is specific to each robot.

imgio currently supports these robots: )

• fit/x: takes an image and produces a new image scaled down to fit into x pixels. The image will never scaled up; if it is too small than width and height will be adjusted to keep the requested aspect ratio.
• fill/x: takes an image and produces a new image scaled down to fit into x pixels. The image will never scaled up; if it is too small than width and height will be adjusted to keep the requested aspect ratio.
• png: convert the image into PNG format. Currently supported only in the left-most position.
• jpg[/quality]: convert the image into JPEG format. Currently supported only in the left-most position.

Deployment

Run

bundle install
bundle exec thin start

How it works

This script parses the URL you pass it, fetches the image at the URL, uses RMagick to convert the image, and spits out the result. Pretty basic stuff, actually.

Caching is important

The HTTP response has the proper cache headers set to cache the result for 1 day (on default). That means each requested image is built only a few times per day - assuming your webserver is configured to use a cache like varnish. Hint: Heroku runs its instances behind a varnish cache.

How to deploy

This is a simple sinatra application. Should work out of the box using the usual sinatra deployment options. How to deploy on heroku

Help improve this script (if you feel like doing so)

• Clone. Extend. Fix. Send pull request.

Development

• Make sure you have ImageMagick installed
• Imgio only works with ruby >= 1.9.
• Bundler is used for dependency management, so use $ bundle install to fetch the needed dependencies
• You can run the included tests with $ rake

Contributors

• @radiospiel
• @sebastianspier
• @Overbryd