Re: [GD-DEVEL] Polygon with holes

On Sep 12, 2007, at 8:34 PM, Mateusz Loskot wrote:
> Hi,
>
> Could anyone provide me with some tricks about what's the best and
> efficiently way to render filled polygon with one or more holes?
> IOW, how to render a donut-like polygon that's filled with red colour
> but internal ring is not filled (is displayed as transparent).

What I ended up doing in a recent project is creating a new paletted  
image buffer of image size and allocate two colors, black and white.  
The black is allocated first and fills the background. Then I drew  
the non-hole parts of the polygon in white, without anti-aliasing.  
(GD's antialiasing isn't great for polygons with dense vertices  
anyway.) Then I drew the holes back in black.

Once that is done, I iterated over the buffer and whenever I found a  
white pixel, I set the correct color on the main image's  
corresponding pixel. Efficient? Maybe not. Simple, yes.

hth,
–natevw