FastImage finds image dimensions fast using minimal resources
Categories rails, ruby | 11 June, 2009 | By Stephen Sykes
I just released a gem to find image dimensions and type information fast. I have previously done some work in this area, but this is a much more comprehensive solution, and fixes problems with certain jpegs.
FastImage finds the size or type of an image given its uri by fetching as little as needed
The problem
Your app needs to find the size or type of an image. This could be for adding width and height attributes to an image tag, for adjusting layouts or overlays to fit an image or any other of dozens of reasons.
But the image is not locally stored – it’s on another asset server, or in the cloud – at Amazon S3 for example.
You don’t want to download the entire image to your app server – it could be many tens of kilobytes, or even megabytes just to get this information. For most image types, the size of the image is simply stored at the start of the file. For JPEG files it’s a little bit more complex, but even so you do not need to fetch most of the image to find the size.
FastImage does this minimal fetch for image types GIF, JPEG, PNG and BMP. And it doesn’t rely on installing external libraries such as RMagick (which relies on ImageMagick or GraphicsMagick) or ImageScience (which relies on FreeImage).
You only need supply the uri, and FastImage will do the rest.
Examples
FastImage.size("http://stephensykes.com/images/ss.com_x.gif")
=> [266, 56] # width, height
FastImage.type("http://stephensykes.com/images/pngimage")
=> :png
Installation
Gem
Rails
Install the gem as above, and configure it in your environment.rb file as below:
Rails::Initializer.run do |config|
…
config.gem "sdsykes-fastimage", :lib=>"fastimage"
…
end
…
Then you’re off – just use FastImage.size() and FastImage.type() in your code as in the examples.
Documentation
RSS
Nice work!
Would it possible to use a more general URL? So local files are treated in the same way?
Another project you may be interested in is http://github.com/andersonbrandon/ruby-imagespec
It gives you the dimensions and content-type of PNG, GIF, JPG, and SWF (Flash movies). You can pass to it a URL, file handle, or a string containing the path to a file.
Jason: yes, I’ll add that feature
Michael: that uses open-uri to fetch the url – I wonder if it fetches only the minimum necessary to get the size. I’ll test it.
Great project. Thanks!
Jason: Version 1.1.1 was just released, and supports reading from local files.
Vesa: Ole hyvä!
Stephen: As of right now I have open-uri just download the whole file. It was a quick hack since I mostly use the lib for local files. I’ll check out fastimage.
Excellent thanks! :)
Hi, I’ve tried this code:
FastImage.size(“http://www.thanhnien.com.vn/News/Picture201001/lop10.jpg”)
=> nil
I can load the image by FireFox, and see its size as 250×188. What’s the problem?
It’s a bug – thanks for the report. Please install version 1.2.6 using sudo gem install fastimage
It works! Thank you. ^^