Antialiased Line Drawing
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To draw antialiased lines on the PixelBlock, mix in the CLineStencil class below and define the four abstract methods. Wu Antialiasing is used for lines that are not horizontal, vertical, or diagonal. You will see in the code comments how you have to choose between including clipping code or testing each pixel is inside the PixelBlock before setting it (code-size versus code speed). It is worth pointing out that the the antialiased line blending can look banded against a black background as shown in the image below. Against lighter backgrounds there is no banding.

class CLinePainter : public CPixelBlock, public CLineStencil {
  WORD GetWidth () const {return CPixelBlock::GetWidth ();}
  WORD GetHeight() const {return CPixelBlock::GetHeight();}
  DWORD* GetPointer(WORD x, WORD y) const {return CPixelBlock::GetPointer(x,y);}
  void   SetPixel(WORD x, WORD y, DWORD Colour) {CPixelBlock::SetPixel(x,y, Colour);}
  void BlendPixel(WORD x, WORD y, DWORD Colour, BYTE Transparency) {CPixelBlock::BlendPixel(x,y, Colour, Transparency);}
public:
  CLinePainter() {}
  virtual ~CLinePainter() {}
};
Wu Antialiased Line Drawing
You can mix in as many 'Stencils' as you like to provide all the primitives you need.

The Colours, Effects and Patterns sections have further extensions.

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 (1936) Last modified: Fri, 12 Jun 2009 11:17:23 +0000