[wxruby-users] chart extension for wxRuby?

[Alex Fenton]

Ellis, Peter wrote:
> Does anyone know of a chart making extension written with wxRuby?  I
> know there are a few Ruby gems out there to make charts (as SVG or an
> image), but they seem to have a lot of overhead associated with them.
> The ones I've found that seem most interesting (Gruff, Scruffy, gnuplot)
> require a big bulky graphics/image processing library to be installed.
> Seems like wxRuby has all the pieces one would need to make a nice chart
> API or custom chart widget,
Yes, all the pieces should be there. There are several charting 
libraries written in C++ for wxWidgets which might offer a good starting 
point [1]

Basically, you use a DC (DeviceContext) to draw lines, polygons, 
ellipses, text etc. DC can draw images from files and do textured fills. 
Wx::Grid would be an excellent component for editing and viewing the 
source data points.

The target canvas can be either the screen (using Window#paint to create 
a PaintDC), or a bitmap (using Bitmap#draw to create a MemoryDC). The 
same actual drawing code is used regardless of the target. Once the 
drawing's been done on a bitmap, call Bitmap.save_file to save the image 
to a variety of formats, including BMP, PNG, TIF or JPG.

For higher-quality output there's also GraphicsContext, which can be 
created by calling GraphicsDC.create(dc) from any other DC. This will 
give anti-aliased edges and also offers gradient fills but is otherwise 
very similar.
> although probably without the SVG, which is fine for my purposes.
>   
There's an SVG-writer as an optional contrib-module in the main 
wxWidgets tree, which allows DC drawing code to be output as SVG. This 
isn't currently porrted to wxRuby, but if there's interest we could have 
a look at adding it.

In my day job I do a lot of charting in Excel and SPSS so I'd be 
interested to hear how it goes if you decide to pursue this.

cheers
alex

[1] 
http://wxcode.sourceforge.net/complist.php?compperpage=1000&viewmode=full&browseby=category&section=graphics&page=1