c#GDI+绘图实时缩放

具体措施：

1. 先获取控件的原大小，然后对需要绘制的控件加入滚轮事件，每次滚动改变控件的大小：

   this.pic.MouseWheel += new MouseEventHandler(pictureBox1_Paint1);
   

2. 滚轮事件中加入线程，线程的存在是为了实时绘制不卡顿，

   private void pictureBox1_Paint1(object sender, MouseEventArgs e) {
               
               this.pic.Width += e.Delta/10;
               this.pic.Height += e.Delta/10;
               if (this.pic.Height < 50) {
                   this.pic.Height = 50;
                   this.pic.Width = 50;
               }
               run();
   }
   private void run() {
               Thread t = new Thread(() => {
                   Graphics g = pic.CreateGraphics();
                   g.Clear(Color.Gray);
                   g.ScaleTransform(this.pic.Width / width1, this.pic.Height / height1);
                   Console.WriteLine($"{this.pic.Width / width1} + {this.pic.Height / height1}");
                   g.DrawRectangle(new Pen(Color.Black), new Rectangle(10, 10, 10, 10));
                   g.Flush();
               });
               t.Start();
   }
   

策略一：

Matrix m = new Matrix();
m.Scale(this.Width / width1, this.Height / height1);
GraphicsPath a = new GraphicsPath();
a.AddRectangle(new RectangleF(100, 100, 50, 50));
a.Transform(m);
g.DrawPath(new Pen(Color.Red), a);

策略二：

Graphics g = pic.CreateGraphics();
g.Clear(Color.Gray);
g.ScaleTransform(this.pic.Width / width1, this.pic.Height / height1);
Console.WriteLine($"{this.pic.Width / width1} + {this.pic.Height / height1}");
g.DrawRectangle(new Pen(Color.Black), new Rectangle(10, 10, 10, 10));
g.Flush();

*注：*因为滚轮导致控件的改变，是可以在控件的重绘事件中捕获的，_Paint(object sender, PaintEventArgs e)。理论上下面是可行的。

private void pictureBox1_Paint(object sender, PaintEventArgs e)
        {
            //Thread t = new Thread(() => {
            //    Graphics g = pic.CreateGraphics();
            //    g.Clear(Color.Gray);
            //    g.ScaleTransform(this.pic.Width / width1, this.pic.Height / height1);
            //    Console.WriteLine($"{this.pic.Width / width1} + {this.pic.Height / height1}");
            //    g.DrawRectangle(new Pen(Color.Black), new Rectangle(10, 10, 50, 50));
            //    g.Flush();
            //});
            //t.Start();
        }

但是md缩放的时候， 不发生重绘事件！ 所以还是直接在滚轮事件中加线程比较合适。