Ruby: Find non-transparent PNG and convert into JPG

Question

What is the smartest way to find out if a PNG has transparency or not in Ruby? Is it OK if I just check if there's an alpha-channel? If yes: How do I check for an alpha-channel?

I'm writing a script that will convert all PNGs without transparency into smaller JPGs.

Thanks a lot for your help!

UPDATE: In the meantime I've written that script and you can find it at Github.

Answer 1

Checking the alpha channel seems the most sensible thing to do. Is it safe to assume you are using RMagick? did you read the documentation?

>> require 'RMagick'
>> image = Magick::Image.read("a.png").first
>> image.alpha?
=> true

http://www.imagemagick.org/RMagick/doc/image1.html#alpha_q