Ampize replaces tags to AMP specific tags and removes prohibited tags and attributes.
If img tag doesn't explictly specify a size Ampize download a source image and set a size to amp-img tag automatically.

Add this line to your application's Gemfile:

gem 'ampize'

And then execute:

$ bundle

Or install it yourself as:

$ gem install ampize

ampize = Ampize::Ampize.new()
result = ampize.transform('<img src="./spec/data/rect.jpg" />')
puts result
>> <amp-img src="./spec/data/rect.jpg" width="100" height="100" layout="responsive"></amp-img>

If img element doesn't have width/height attributes then Ampize download an image to get a dimension. Ofcourse if img element have a size Ampize keep it.

Currently Ampize doesn't support amp-audio, amp-video. Your contribution is always welcome.

Bug reports and pull requests are welcome on GitHub at https://github.com/dotneet/ampize.