基于C#实现用于显示照片的屏保

摘要

Windows XP已经带了一个屏保程序，让用户可以现实照片，只要你将这些照片放于指定目录。 但是照片不是全屏；本篇基于全屏显示照片；照片位置在注册表中。

实现

1 屏保程序框架

屏保程序有命令行四个参数：

               case "/a": //密码对话框实现代码

                    MessageBox.Show("passwd not set for this screen saver.");

                    Application.Exit();

                    break;

                case "/c": //参数设置实现代码

                    MessageBox.Show("parameter not set for this screen saver.");

                    Application.Exit();

                    break;

                case "/p": //预览实现代码

                    Cursor.Hide();

                    m_ifPrev = true;

                    startTimer();

                    break;

                case "/s": //正常运行实现代码

                    Cursor.Hide();

                    startTimer();

                   break;

                default: stopScreen(); break;

一般而言，预览和正常运行时必须要处理的。

2 可调参数

屏保程序由俩个可调参数：自动播放的间隔时间和照片目录。本程序用注册表处理。

            RegistryKey rkScr = null;

            RegistryKey rk = Registry.LocalMachine.OpenSubKey(location);

            string[] subkeys = rk.GetSubKeyNames();

            foreach (string s in subkeys)

            {

                if (s == key_name)

                {

                    rkScr = rk.OpenSubKey(s);

                    m_default_path = (string)rkScr.GetValue(key_path_name);

                    int interval = (int)rkScr.GetValue(key_interval_name);

                    m_interal = interval > 1000 ? interval : 1000;

                    rk.Close();

                    break;

                }

            }

            if (rkScr == null)

            {

                rkScr = rk.CreateSubKey(key_name, RegistryKeyPermissionCheck.ReadWriteSubTree);

                rkScr.SetValue(key_path_name, m_default_path);

                rkScr.SetValue(key_interval_name, m_interal);

                rk.Close();

            }

3 读取文件信息

图片不能一开始就加载，这样占用太多内存。只能在Timer的回调中处理，释放前一张图片空间，加载新照片。

但是图片信息可以初始化时准备好，主要是图片的路径名。

        private void getAllFile()

        {

            if (Directory.Exists(m_default_path))

            {

                DirectoryInfo di = new DirectoryInfo(m_default_path);

                try

                {

                    foreach (FileInfo fi in di.GetFiles())

                    {

                        if (fi.Extension == ".jpg")

                        {

                            m_pics.Add(fi.FullName);

                        }

                    }

                }

                catch (Exception e)

                {

                    MessageBox.Show(e.Message);

                }

            }

        }

特别是对文件过滤的处理要注意，否则会生成一个thumbs.db文件，导致下次运行时抛出OutOfMemory异常。这里不过滤文件也可以，但是必须Image实例创建时捕获一场并处理。

            try

            {

                if (m_ie.MoveNext())

                {

                    m_img = Image.FromFile(m_ie.Current);

                    m_brush.Interval = m_interal > 2000 ? m_interal - 1000 : m_interal / 2;

                    m_brush.Tick += new EventHandler(m_brush_Tick);

                    m_brush.Start();

                    Invalidate();

                }

                else

                {

                    m_ie.Reset();

                }

            }

            catch (InvalidOperationException ioe)

            {

                MessageBox.Show(ioe.Message);

            }

            catch (OutOfMemoryException ome)

            {

                MessageBox.Show(ome.Message + " when read file:" + m_ie.Current);

                this.m_pics.Remove(m_ie.Current);

                m_img.Dispose();

                m_ie = m_pics.GetEnumerator();

            }

            catch (FileNotFoundException fnfe)

            {

                MessageBox.Show("file " + fnfe.FileName + " not found");

            }

            catch(Exception ex)

            {

                MessageBox.Show(ex.Message);

            }

            finally

            {

                //stopScreen();

            }

 

 

Image类可以参考MSDN。

4 绘图

必须重载Form类的OnPaint函数。

        protected override void OnPaint(PaintEventArgs e)

        {

            if (!m_ifDrawBg)

            {

 

                if (m_img != null)

                {

                    //e.ClipRectangle();

                    Graphics g = e.Graphics;

                    Rectangle rect;

                    if (m_img.Size.Width > m_img.Size.Height)

                    {

                        rect = new Rectangle(this.Left, this.Top,

                            this.Left + this.Width, this.Top + this.Height);

                    }

                    else

                    {

                        double scale = (double)m_img.Size.Width / (double)m_img.Size.Height;

                        rect = new Rectangle(this.Width / 4, this.Top,

                            this.Left + (int)(scale * this.Height), this.Top + this.Height);

                    }

                    m_DrawArea = rect;

                    g.DrawImage(m_img, rect);                   

                }               

            }

            else

            {

                Graphics g = e.Graphics;

                g.FillRectangle(m_blkBrush, m_DrawArea);

                m_ifDrawBg = false;

            }

            base.OnPaint(e);

        }

这里根据图片大小，作了一个全屏的处理。

5 全屏

全屏的关键是计算绘图区域，去PrimaryScreen的边界。

            this.Width = Screen.PrimaryScreen.Bounds.Width;

            this.Height = Screen.PrimaryScreen.Bounds.Height;

            this.Size = new System.Drawing.Size(this.Width, this.Height);

            this.Left = 0;

            this.Top = 0;

            m_DrawArea.X = this.Left;

            m_DrawArea.Y = this.Top;

            m_DrawArea.Width = this.Width;

            m_DrawArea.Height = this.Height;

            this.BackColor = Color.Black;

            this.FormBorderStyle = FormBorderStyle.None;

            this.ShowInTaskbar = false;

6 定时器

为了图片自动浏览效果比较舒服，这里使用了3个定时器：

• 自动播放定时器，播放照片，启动刷屏定时器；
• 延时定时器：接受键盘和鼠标事件，避免屏保启动时立即退出。
• 刷屏定时器：在显示上一幅图后用黑色brush清空屏幕。

 

结束语

基于C#实现屏保非常方便，主要是图片显示有C#的Image类处理；另外，有了MFC的基础，绘图操作也容易了。