title: Antialiased composition by coverage?
body: <p>Does anyone know of a graphics system which handles composition of multiple anti-aliased lines well? </p>
  
  <p>I'm showing a dependency diagram and have a bunch of curves emanating from a point. These are drawn anti-aliased in the usual way, of blending partially covered pixels. So if two lines would occupy the same half of a pixel, the antialiasing blends it to 75% filled rather than 50% filled. With enough lines drawn on top of each other, the pixel blend clamps and you end up with aliased lines.</p>
  
  <p>I know anti-grain geometry has algorithms for calculating blends which cater for lines which abut, and that oversampling might work, but are there any other approaches?</p>