C# 获取图片一部分

Bitmap   mybit=new   Bitmap(100,100);//局部大小 

Graphics   g=Graphics.FromImage(mybit); 

g.DrawImage(oldbit/*原图*/, 

        new   Rectangle(new   Point(0,0),new   Size(100,100)),//目标位置 

        new   Rectangle(new   Point(startX,startY),new   Size(100,100)),//原图位置 

        GraphicsUnit.Pixel);