wxruby users - Sep 2008 - render natively

I would like to render natively i.e. via a C dll that I have wrapped
using SWIK.

So I want my c code to receive a buffer that it can render to, and then
have WXruby display this memory buffer/bitmap.

Can anyone advise me what would be the best method for doing this, to
save me having to find out the hard way.

Many thanks,
Jim.
-- 
Posted via http://www.ruby-forum.com/.

Jim flip wrote:
> I would like to render natively i.e. via a C dll that I have wrapped
> using SWIK.
>
> So I want my c code to receive a buffer that it can render to, and then
> have WXruby display this memory buffer/bitmap.
>   
A drawing context (whether an in-memory buffer, an on-screen canvas, or 
a printout) is represented by a DC [1] instance in wxRuby. MemoryDC is 
the specific class for in-memory buffers.

However the API and class is cross-platform and specific to WxRuby, so 
you''re not going to be able to pass this in directly to your dll. You 
don''t give a lot of info about the way your API works, but I''d
think
probably the easiest way would be to have your dll render to a ruby 
String in a recognised image format (wxRuby understands PNG, TIF, JPG, 
BMP, TGA) then wrap this in a ruby StringIO object.

Call Wx::Image.read [2] to load this image into an object, then do 
Wx::Bitmap.from_image to convert it to a windows bitmap that can be 
rendered on screen. Lastly, simple draw this onto a window surface using 
its paint method. Have a look at the example in samples/drawing/image.rb 
to see the basics of writing an image to screen.
> Can anyone advise me what would be the best method for doing this, to
> save me having to find out the hard way.
>   
This should probably work, but there''s a few other options should this 
not be suitable. Also have a search through the archives as there have 
been a few threads about rendering images from external libraries (eg 
ImageMagick).

cheers
alex


[1] http://wxruby.rubyforge.org/doc/dc.html
[2] http://wxruby.rubyforge.org/doc/image.html#Image_read

Thanks for the pointers, I think I will try using a bitmap and it''s 
set_data method as this should be simple to try out but may be a bit 
slow.

Thanks,
Jim.
-- 
Posted via http://www.ruby-forum.com/.

Jim flip wrote:
> Thanks for the pointers, I think I will try using a bitmap and
it''s
> set_data method as this should be simple to try out but may be a bit 
> slow.
>   
If you can avoid composing or decomposing the image data in Ruby (using 
pack etc) this will be pretty fast - for example, if you can get your 
extension to emit image data in that format. Then it''s just a C-level 
memcpy going on.

Similarly Image.read should be fast if you can get your extension to 
produce a known image format. These wxRuby methods are not particularly 
far off the native C library functions in libtiff, libpng etc

alex