Re: Problems with outline rasterizer

> -----Original Message-----
> From: Jim Barry [mailto:jim@...]
> Sent: Wednesday, June 10, 2009 3:30 PM
> To: Anti-Grain Geometry
> Subject: [AGG] Problems with outline rasterizer
>
> Hi Folks,
>
> I noticed that the outline rasterizer fails to draw empty (or nearly-
> empty) rectangles. For example, consider a rectangle with vertices ABCD
> and zero height. The sequence of events goes like this:
>

>
> Now the zero-height rectangle will be drawn as a line. Does this seem
> like a reasonable fix, or might it cause other problems?
>
> Also, the outline rasterizer will "optimize" away rectangles with
> single-pixel width/height, because it considers points at a distance of
> 1.5 times the subpixel scale or closer to be coincident. Presumably
> Maxim had a reason for choosing this threshold, but I propose changing
> line_aa_vertex::operator() from this:
>
>   bool operator () (const line_aa_vertex& val)
>   {
>     float_type dx = val.x - x;
>     float_type dy = val.y - y;
>     return (len = uround(sqrt(dx * dx + dy * dy))) >
>       (line_subpixel_scale + line_subpixel_scale / 2);
>   }
>
> to this:
>
>   bool operator () (const line_aa_vertex& val)
>   {
>     float_type dx = val.x - x;
>     float_type dy = val.y - y;
>     return (len = uround(sqrt(dx * dx + dy * dy))) >=
> line_subpixel_scale;
>   }
>
> Comments?
>
> - Jim