WPF雙緩存繪製圖形

1、雙緩存：把複雜的繪圖過程寫到內存裏，然後把內存裏的內容一次性的貼到要顯示的元素上。耗資源少、畫面流暢。

2、使用WriteableBitmap。

3、繪製到Image上：

width = (int)OutCanvas.ActualWidth;
height = (int)OutCanvas.ActualHeight;
if (width > 0 && height > 0)
{
    DisplayImage.Width = width;
    DisplayImage.Height = height;
 
    wBitmap = new WriteableBitmap(width, height, 72, 72, PixelFormats.Bgr24, null);
    DisplayImage.Source = wBitmap;
}

4、要使用GDI+：先把WriteableBitmap的後臺緩存交給Bitmap管理，然後使用Bitmap的Graphics進行繪製。

wBitmap.Lock();
Bitmap backBitmap = new Bitmap(width, height, wBitmap.BackBufferStride, System.Drawing.Imaging.PixelFormat.Format24bppRgb, wBitmap.BackBuffer);
 
Graphics graphics = Graphics.FromImage(backBitmap);
graphics.Clear(System.Drawing.Color.White);//整張畫布置爲白色
 
//畫一些隨機線
Random rand = new Random();
for (int i = 0; i < 100; i++)
{
    int x1 = rand.Next(width);
    int x2 = rand.Next(width);
    int y1 = rand.Next(height);
    int y2 = rand.Next(height);
    graphics.DrawLine(Pens.Red, x1, y1, x2, y2);
}
 
graphics.Flush();
graphics.Dispose();
graphics = null;
 
backBitmap.Dispose();
backBitmap = null;
 
wBitmap.AddDirtyRect(new Int32Rect(0, 0, width, height));
wBitmap.Unlock();