From: Timothy Hunter <cyclists@...>
Date: 2005-12-31T20:09:28+09:00
Subject: Re: Making screenshots with Ruby

guest@guest.com wrote:
> Oh and forgot to add - I'm using them later with RMagick, so I'd want 
> them loaded in memory in a way that RMagick can understand them, but if 
> it has to it can be saved to file too :)
> 
There are a couple of ways to construct an RMagick image without reading 
an image file. If the screenshot data is in a Ruby string in one of the 
formats that ImageMagick/GraphicsMagick understands (JPEG, GIF, BMP, or 
one of the 80+ others) then you can use Image.from_blob[1].

If the screenshot data is in a Ruby string (or an instance of any class 
with a to_str method, such as NArray) and is simply "raw" pixel data in 
scanline order (left-to-right, top-to-bottom) you use the 
Image.import_pixels method. It's blindingly fast. (I'd give you a URL to 
the doc, but the online doc is sufficiently out-of-date that it doesn't 
describe how import_pixels exploits to_str. You can get the details from 
your local copy of the RMagick doc.)

[1] http://www.simplesystems.org/RMagick/doc/image1.html#from_blob