Winform设计不规则窗体

创建不规则窗体，首先需要设计一个透明部分的 alpha值小于10的图片，推荐PNG格式

        ///<summary>
        /// 设置不规则窗体
        ///</summary>
        ///<param name="sender"></param>
        ///<param name="e"></param>
        private void Login_Load(object sender, EventArgs e)
        {
            //从指定的位图中获取alpha透明度大于 10 的区域
            Bitmap img = (Bitmap)pictureBox1.Image; 
            GraphicsPath grapth = GetNoneTransparentRegion(img, 10); 
            this.Region = new Region(grapth);
           
            //要显示的图片设置为窗体背景
            this.BackgroundImage = pictureBox1.Image; 
            this.BackgroundImageLayout = ImageLayout.Zoom; 
            
            //在修改窗体尺寸之前设置窗体为无边框样式
            this.FormBorderStyle = FormBorderStyle.None;
            this.Width = pictureBox1.Image.Width;
            this.Height = pictureBox1.Image.Height;
        }

        ///<summary> 
        /// 返回指定图片中的非透明区域(方法)
        ///</summary> 
        ///<param name="img">位图</param> 
        ///<param name="alpha">alpha 小于等于该值的为透明</param> 
        ///<returns></returns>
        public static GraphicsPath GetNoneTransparentRegion(Bitmap img, byte alpha)
        {
            int height = img.Height;
            int width = img.Width;
            int xStart, xEnd;
            GraphicsPath grpPath = new GraphicsPath();
            for (int y = 0; y < height; y++)
            {
                //逐行扫描      
                for (int x = 0; x < width; x++)
                {
                    //略过连续透明的部分          
                    while (x < width && img.GetPixel(x, y).A <= alpha)
                    {
                        x++;
                    }
                    //不透明部分；   
                    xStart = x;
                    while (x < width && img.GetPixel(x, y).A > alpha)
                    {
                        x++;
                    }
                    xEnd = x;
                    if (img.GetPixel(x - 1, y).A > alpha)
                    {
                        grpPath.AddRectangle(new Rectangle(xStart, y, xEnd - xStart, 1));
                    }
                }
            }
            return grpPath;
        }