_beginPaint _impl beginPaint beginPaintBuffered beginPath bezierTo clearCachedBitmap clearRect clearWindow clipPath clipRect closePath drawBitmap drawCachedBitmap drawCachedBitmap2 drawEllipse drawHandle drawLine drawPath drawRect drawTextAt endPaint getEncoder GiGdipCanvas hasCachedBitmap isBufferedDrawing lineTo moveTo quadTo restoreClip save saveCachedBitmap saveClip setBrush setPen thumbnailImage ~GiGdipCanvas

beginPaintBuffered() bool GiGdipCanvas::beginPaintBuffered ( int  width, int  height, COLORREF  bkcolor = (COLORREF)-1  ) 给定缓冲位图的大小，开始绘制并清除背景