C#表單上繪製矩形

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先上

 

 

 

滑鼠三個事件

 

private void Form1_MouseDown(object sender, MouseEventArgs e)        {            //記錄開始點            this.mousedown = true;            this.startpoint = e.Location;        }        private void Form1_MouseMove(object sender, MouseEventArgs e)        {            //記錄結束點。繪製到視窗上            if (mousedown)            {                this.endpoint = e.Location;                this.Refresh();                gform.DrawImage(this.bmsave, new Point(0, 0));                Rectangle rect = new Rectangle();                this.rect_play(ref rect);                gform.DrawRectangle(new Pen(Color.Black), rect);            }        }        private void Form1_MouseUp(object sender, MouseEventArgs e)        {            //記錄結束點。繪製到bitmap上            this.endpoint = e.Location;            this.mousedown = false;            Rectangle rect = new Rectangle();            this.rect_play(ref rect);            g.DrawRectangle(new Pen(Color.Black), rect);            gform.DrawImage(this.bmsave, new Point(0, 0));        }

 

 

 

根據startpoint和endpoint兩個點去確定要畫的矩形Location和width，heigth

 

        private void rect_play( ref Rectangle rect)        {            //根據兩個點確定矩形的左上方點Location            if (this.startpoint.X > this.endpoint.X && this.startpoint.Y < this.endpoint.Y)            {                rect.Location = new Point(this.endpoint.X, this.startpoint.Y);            }            else if (this.startpoint.X < this.endpoint.X && this.startpoint.Y > this.endpoint.Y)            {                rect.Location = new Point(this.startpoint.X, this.endpoint.Y);            }            else if (this.startpoint.X > this.endpoint.X && this.startpoint.Y > this.endpoint.Y)            {                rect.Location = this.endpoint;            }            else            {                rect.Location = this.startpoint;            }            //擷取兩點的X,Y距離            rect.Width = Math.Abs(this.startpoint.X - this.endpoint.X);            rect.Height = Math.Abs(this.startpoint.Y - this.endpoint.Y);                        if (rect.Width == 0 && rect.Height == 0)            {                //防止誤點的時候進行繪製            }            else if (rect.Width == 0)            {                rect.Width = 1;            }            else if (rect.Height == 0)            {                rect.Height = 1;            }        }

 

 

完整執行個體代碼連結：http://pan.baidu.com/s/1sjkpic1

 

畫的時候視窗閃的特別厲害啊，因為大量的Refresh和Draw，開雙緩衝也不起多大作用

遲點有時間用QT c++做一個，QT寫出來的應該是不會閃爍的

 

C#表單上繪製矩形