C#雪花飘研究和学习

        前几天在csnd的下载频道下载了一个C#写的雪花飘飘的程序，感觉很是惊讶，于是庖丁解牛，仔细的研究了一番。再次贴出来，以供下次学习。具体效果如下图：

其中是实现的思路是利用WinAPI，创建一个窗口句柄，然后再找个句柄窗口中去绘图和更新。

具体核心利用到的API如下

[DllImport("gdi32.dll")]
        public static extern IntPtr CreateCompatibleDC(IntPtr hDC);

        [DllImport("gdi32.dll")]
        public static extern Bool DeleteObject(IntPtr hObject);

        [DllImport("user32.dll")]
        public static extern IntPtr GetDC(IntPtr handle);
        [DllImport("gdi32.dll")]
        public static extern IntPtr DeleteDC(IntPtr handle);

        [DllImport("user32.dll", ExactSpelling = true)]
        public static extern int ReleaseDC(IntPtr handle, IntPtr hObject);

        [DllImport("gdi32.dll")]
        public static extern IntPtr SelectObject(IntPtr hDC, IntPtr hObject);

        [DllImport("User32.dll")]
        public static extern Bool UpdateLayeredWindow(IntPtr handle, IntPtr hdcDst, ref Point pptDst, ref Size psize, IntPtr hdcSrc, ref Point pprSrc, int crKey, ref BLENDFUNCTION pblend, int dwFlags);

而实现绘制的思路如下：

private void SetBackground(Image img)
        {
            try
            {
                Bitmap bitmap = (Bitmap)img;
                if (bitmap.PixelFormat != PixelFormat.Format32bppArgb)
                {
                    throw new ApplicationException();
                }

                IntPtr hObject = IntPtr.Zero;
                IntPtr zero = IntPtr.Zero;
                IntPtr hDC = Win32.GetDC(IntPtr.Zero);
                IntPtr ptr2 = Win32.CreateCompatibleDC(hDC);

                try
                {
                    hObject = bitmap.GetHbitmap(Color.FromArgb(0));
                    zero = Win32.SelectObject(ptr2, hObject);
                    Win32.Size size2 = new Win32.Size(bitmap.Width, bitmap.Height);
                    Win32.Size psize = size2;
                    Win32.Point point3 = new Win32.Point(0, 0);
                    Win32.Point pprSrc = point3;
                    point3 = new Win32.Point(base.Left, base.Top);
                    Win32.Point pptDst = point3;
                    point3 = new Win32.Point(base.Left, base.Top);
                    Win32.BLENDFUNCTION pblend = new Win32.BLENDFUNCTION();
                    pblend.BlendOp = 0;
                    pblend.BlendFlags = 0;
                    pblend.SourceConstantAlpha = 0xff;
                    pblend.AlphaFormat = 1;
                    Win32.UpdateLayeredWindow(this.Handle, hDC, ref pptDst, ref psize, ptr2, ref pprSrc, 0, ref pblend, 2);
                }
                catch (Exception exception1)
                {
                    Exception exception = exception1;
                    throw exception;
                }
                finally
                {
                    Win32.ReleaseDC(IntPtr.Zero, hDC);
                    if (hObject != IntPtr.Zero)
                    {
                        Win32.SelectObject(ptr2, zero);
                        Win32.DeleteObject(hObject);
                    }
                    Win32.DeleteDC(ptr2);
                }
            }
            catch(Exception e)
            {
                MessageBox.Show(e.Message);
            }
        }

而根据找个实现的思路可以做出很多很炫的东西，比如透明或者半透明的软件窗体。因为主要的实现是API，所以可以使用C/C++实现超炫的界面。稍后我试试利用找个原理去做一个C#软件的登陆界面。

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