It’s been on the CPAN for a few weeks, but I’ve not taken the time to pontificate about what exactly Graphics::Primitive and its cadre of helpers are.

Backstory

I started working on Chart::Clicker quite a while back. I’d just come from a job as a senior Java developer and still had AWT and Swing on the brain. I’d developed a custom charting package in perl a few months before but wasn’t happy with the results. I sought out a solid charting package to emulate and was heavily inspired by JFreeChart. One of the side effects of this was my disappointment with the availability of general graphics packages on the CPAN. I was jealous of the simple classes in Java that reduced a lot of the work in making graphics: Point, Rectangle, Color and more.

I released Chart::Clicker and was happy. I had emulated a lot of the ideas inside Clicker, writing general Component, Font, Color and Border classes, to name a few. As time went by and people began using Clicker it because clear to me that these concepts could be generalized and turned into a general framework for creating graphics. Thus became Graphics::Primitive.

Enter Graphics::Primitive

Graphics::Primitive is a collection of objects that allow you build a 2d “scene”. The building block of these scenes is a Component. It has a width and height, colors (fore and back), borders, insets and padding. A Container builds on Component and yields a component that can contain other components. To allow for more than plain ol’ boxes Graphics::Primitive provides TextBox, Canvas and Image. While these entities are all pretty simple, but you can create complex results by nesting them.

Creating Output

Graphics::Primitive is really just a data structure. It doesn’t actually do any drawing. Drawing is done by Drivers. The only driver at present is Cairo. It makes a great first driver, however, as it provides PDF, PostScript, PNG and SVG output.

Layout

Graphics::Primitive also doesn’t concern itself with laying out your components. Graphics::Primitive will leave components wherever you put them if left to its own devices. To handle automatic layout management I created Layout::Manager. As you add components to a container you can provide constraints for them. Then you can ask an instance of Layout::Manager to “layout” your container (and any containers contained in it). This concept is borrowed from Java’s layout managers. It is worth noting that each container has it’s own Layout::Manager so you can choose the one that is most fitting for the look you desire.

Benefits

Graphics::Primitive allows you to separate your data from your presentation. Creating an artifact in Graphics::Primitive allows you to change the output format. Need a PDF and a PNG? There’s no reason to rely on a conversion tool or a separate rendering path. Simply clone the component to pass it to each driver.

What Can You Do With it?

The aforementioned Chart::Clicker is made using Graphics::Primitive. You can look over examples of its output. The examples are all pngs but any of those can be converted to any of the formats supported by the Cairo driver by changing a single parameter.

There is a Catalyst view, which I released onto CPAN today. This allows you to serve your components via HTTP.

Document::Writer aims to abstract the underlying Graphics::Primitive components into an API friendly to creating documents. It will likely change quite a bit as I refine the ideas and increase underlying features.

Supporting Cast

I created a handful of other modules in an effort to reduce the work others might do when building similar code.

Graphics::Color provides simple objects for various color spaces. I’ve got a list of color spaces to add, as well as conversion routines.

Geometry::Primitive provides simple geometry entities such as Point, Circle and Rectangle. These objects serve as the base for Graphics::Primitive.

Future Plans

I’m currently sitting on code that allows serialization of a Graphic::Primitive scene using MooseX::Storage, but some API conflicts are stopping me from releasing until I work them out.

Document::Writer will be getting lots of new features as I back out a lot of my crappy text code for a more robust text-layout engine based on Pango. There are supposedly bindings coming for perl that are not tied to GTK+.

Conclusion

Graphics::Primitive has been a lot of fun. If I’d known what I was getting into I probably would’ve run away screaming. There have been many nights that I couldn’t sleep because a problem was rolling around my brain and I had to get up and hack on it for a few hours.

Please check it out and feel free to hit me up with ideas and suggestions. I’ll be giving a talk, hopefully, at PPW 2008. The presentation itself is made in Graphics::Primitive, just for extra oomph.

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Posted at : September 4th, 2008 - 5:33 pm
Filed under : Catalyst, Chart::Clicker, Code, General, Languages, Perl, Work
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