FastImage finds image dimensions fast using minimal resources

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 neededThe problemYour 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

require ‘fastimage’

=> [266, 56]  # width, height
=> :png


sudo gem install sdsykes-fastimage -s

RailsInstall the gem as above, and configure it in your environment.rb file as below: do |config|

config.gem “sdsykes-fastimage”, :lib=>“fastimage”


Then you’re off – just use FastImage.size() and FastImage.type() in your code as in the examples.Documentation


13 thoughts on “FastImage finds image dimensions fast using minimal resources

  1. Jason: yes, I’ll add that featureMichael: 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.

  2. 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.

  3. It’s a bug – thanks for the report. Please install version 1.2.6 using sudo gem install fastimage

  4. Thanks for a wonderful project. However, when I tried:FastImage.size("")=> nilI can load this image in browser, or get its dimensions by using"").first.rows and"").first.columnsThanks,– Phuc

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