Ruby: How do I overlay images on top of another WITHOUT Imagemagick?

Question

I have an image that is 100 X 100, and want to center it in a blank white image that is 200 X 200.

How would I do so with ImageScience and Ruby, or another third party package? And without ImageMagick nor FreeImage? I know that's very constraining but those 2 are being rather lame to me as both don't work on my local Mac and my EngineYard Amazon instance. I am able to use FreeType with Ruby on my Mac, but it fails to deploy on Amazon cloud. I can't install RMagick on my Mac, but it can install on my Amazon cloud.

As an aside, I feel ImageMagick should be installed automatically in every Linux and Mac machine. Would save some people lots of trouble. So much pain for so little value.

Answer 1

The best way would be to use a pure ruby library, such as http://docs.seattlerb.org/png/ from Seattle.rb or https://github.com/wvanbergen/chunky_png

It's quite easy to follow. You should create a white 200x200 canvas and load your image onto it, or if you find it easier, compose images using alpha blending.

(from chucky's examples):

# Compose images using alpha blending.
avatar = ChunkyPNG::Image.from_file('avatar.png')
badge  = ChunkyPNG::Image.from_file('no_ie_badge.png')
avatar.compose!(badge, 10, 10)
avatar.save('composited.png', :fast_rgba) # Force the fast saving routine.

If you don't really need a new image and it's only for displaying pourposes, using css and/or javascript would be much easier.

Answer 2

Sidestepping the question maybe, but did you try installing ImageMagick on your Mac through Homebrew? This is as simple as just installing Homebrew and typing one command:

brew install imagemagick

This should work without any problems at all. Homebrew is like the package manager that should have been included by default in Mac OS X. I also use it to install other packages not included by default, like Git, Ack, Graphviz, ...