public interface

AATileGenerator

sun.java2d.pipe.AATileGenerator
Known Indirect Subclasses

Class Overview

The API for an object that generates alpha coverage tiles for a given path. The RenderingEngine will be consulted as a factory to return one of these objects for a given Shape and a given set of rendering attributes. This object will iterate through the bounds of the rendering primitive and return tiles of a constant size as specified by the getTileWidth() and getTileHeight() parameters. The iteration order of the tiles will be as specified by the pseudo-code: 

     int bbox[] = {left, top, right, bottom};
     AATileGenerator aatg = renderengine.getAATileGenerator(..., bbox);
     int tw = aatg.getTileWidth();
     int th = aatg.getTileHeight();
     byte tile[] = new byte[tw * th];
     for (y = top; y < bottom; y += th) {
         for (x = left; x < right; x += tw) {
             int a = aatg.getTypicalAlpha();
             int w = Math.min(tw, right-x);
             int h = Math.min(th, bottom-y);
             if (a == 0x00) {
                 // can skip this tile...
                 aatg.nextTile();
             } else if (a == 0xff) {
                 // can treat this tile like a fillRect
                 aatg.nextTile();
                 doFill(x, y, w, h);
             } else {
                 aatg.getAlpha(tile, 0, tw);
                 handleAlpha(tile, x, y, w, h);
             }
         }
     }
     aatg.dispose();
The bounding box for the iteration will be returned by the RenderingEngine via an argument to the getAATileGenerator() method.

Summary

Public Methods
abstract void dispose()
Disposes this tile generator.
abstract void getAlpha(byte[] tile, int offset, int rowstride)
Gets the alpha coverage values for the current tile.
abstract int getTileHeight()
Gets the height of the tiles that the generator batches output into.
abstract int getTileWidth()
Gets the width of the tiles that the generator batches output into.
abstract int getTypicalAlpha()
Gets the typical alpha value that will characterize the current tile.
abstract void nextTile()
Skips the current tile and moves on to the next tile.

Public Methods

public abstract void dispose ()

Disposes this tile generator. No further calls will be made on this instance.

public abstract void getAlpha (byte[] tile, int offset, int rowstride)

Gets the alpha coverage values for the current tile. Either this method, or the nextTile() method should be called once per tile, but not both.

public abstract int getTileHeight ()

Gets the height of the tiles that the generator batches output into.

Returns
  • the height of the standard alpha tile

public abstract int getTileWidth ()

Gets the width of the tiles that the generator batches output into.

Returns
  • the width of the standard alpha tile

public abstract int getTypicalAlpha ()

Gets the typical alpha value that will characterize the current tile. The answer may be 0x00 to indicate that the current tile has no coverage in any of its pixels, or it may be 0xff to indicate that the current tile is completely covered by the path, or any other value to indicate non-trivial coverage cases.

Returns
  • 0x00 for no coverage, 0xff for total coverage, or any other value for partial coverage of the tile

public abstract void nextTile ()

Skips the current tile and moves on to the next tile. Either this method, or the getAlpha() method should be called once per tile, but not both.