利用GDI+圖形雙重緩衝（Double Buffering）來實作圖形跑馬燈
之前實作過文字跑馬燈後，應同事要求再實作出圖形跑馬燈，原因無他，因為客戶要求文字跑馬燈後，可預期的圖形跑馬燈的需求一定接踵而至，話不多說了，直接看程式碼。
在這次的程式碼中，依然動態的調用PictureBox來當作我們的基礎繪製畫布，如此一來可以避免直接在Form表單底圖作畫，產生許多效能上的問題。當然，這個類別也提供了事件供給外部程式碼掛載，可以在動態運行的時期藉以觀察相關的參數（若有需要可以自己調整參數）。此外，我這些類別都是寫給自己用的，所以許多的建構或方法，都沒有詳細地進行初始化的檢查，也就是說，當類別的實例被生成之後，相關的欄位或方法的指定，請依照順序來進行，否則可能會跳出null Exception，這並不是因為程式碼寫的爛，純粹是因為這是自用（程式設計師使用），而非用嚴謹的商業元件角度來撰寫。
MarqueeImage文字跑馬燈類別原始程式碼
程式碼裡面依然有透過System.Reflection反射方法，來調用Windows Forms被保護（protected）的SetStyle、UpdateStyles方法，因此你不需要再去Form建構子中，去設定啟用OptimizedDoubleBuffer。
namespace Slashview
{
/// <summary>
/// MarqueeImage事件委派器
/// </summary>
/// <param name="sender">MarqueeText實例本體</param>
/// <param name="e">參數包</param>
public delegate void MarqueeImageEventHandler(System.Object sender, System.EventArgs e);
/// <summary>
/// MarqueeImage主類別
/// </summary>
public class MarqueeImage
{
//（私有變數）圖片顯示元件
private System.Windows.Forms.PictureBox _oTargetPictureBox;
//（私有變數）計時器物件
private System.Windows.Forms.Form _oTargetForm;
//（私有變數）計時器物件
private System.Timers.Timer _oTimer;
//（私有變數）兩張圖片中間的指標
private int _iPartitionPoint;
/// <summary>
/// 提供螢幕畫面重新繪製時的外部事件通知
/// </summary>
public event MarqueeImageEventHandler OnDrawing;
/// <summary>
/// 圖片要畫在哪一個表單物件的繪布上
/// </summary>
public System.Windows.Forms.Form oTargetForm
{
get { return _oTargetForm; }
set
{
_oTargetForm = value;
//阻擋違法的建構參數
if (iWidth == 0 || iHeight == 0) { throw new System.Exception("預設圖片的寬度與高度不可能為零。"); }
//動態產生PictureBox
if (_oTargetPictureBox == null)
{
_oTargetPictureBox = new System.Windows.Forms.PictureBox()
{
Left = iPosX,
Top = iPosY,
BorderStyle = System.Windows.Forms.BorderStyle.None,
Size = new System.Drawing.Size(iWidth, iHeight),
ClientSize = new System.Drawing.Size(iWidth, iHeight)
};
_oTargetForm.Controls.Add(_oTargetPictureBox);
SetDoubleBuffering(_oTargetPictureBox);
//強制重繪PictureBox
_oTargetPictureBox.Refresh();
}
}
}
/// <summary>
/// 圖片要顯示在哪個X軸上
/// </summary>
public int iPosX { get; set; }
/// <summary>
/// 圖片要顯示在哪個Y軸上
/// </summary>
public int iPosY { get; set; }
/// <summary>
/// 圖片預期寬度
/// </summary>
public int iWidth { get; set; }
/// <summary>
/// 圖片預期高度
/// </summary>
public int iHeight { get; set; }
/// <summary>
/// 圖片幾千分之一秒移動一次
/// </summary>
public int iTimerInterval { get; set; }
/// <summary>
/// 圖片每次要移動幾個像素
/// </summary>
public int iMovePixel { get; set; }
/// <summary>
/// 當前圖片物件
/// </summary>
public System.Drawing.Image oCurrentImage { get; set; }
/// <summary>
/// 下張圖片物件
/// </summary>
public System.Drawing.Image oNextImage { get; set; }
/// <summary>
/// 開始移動圖片
/// </summary>
public void Start()
{
if (iTimerInterval <= 0) { throw new System.Exception("計數器必須被設定，或已經設定的整數值有誤。"); }
if (_oTimer != null) { _oTimer.Stop(); }
_oTimer = new System.Timers.Timer() { Interval = iTimerInterval };
_oTimer.Elapsed += DrawMarquee;
_oTimer.SynchronizingObject = _oTargetPictureBox;
_iPartitionPoint = oCurrentImage.Width;
_oTimer.Start();
}
/// <summary>
/// 結束移動圖片
/// </summary>
public void Stop()
{
if (_oTimer == null) { return; }
_oTimer.Stop();
_oTimer.Dispose();
}
/// <summary>
/// 繪製圖形跑馬燈
/// </summary>
public void DrawMarquee(System.Object sender, System.EventArgs e)
{
if (_oTargetForm == null || _oTargetPictureBox == null) { throw new System.Exception("未指定繪製目標表單，或者是建立繪圖元件失敗。"); }
/* 進行繪圖作業 */
using (System.Drawing.BufferedGraphics oBuffer = System.Drawing.BufferedGraphicsManager.Current.Allocate(_oTargetPictureBox.CreateGraphics(), _oTargetPictureBox.ClientRectangle))
{
using (System.Drawing.Graphics oGraph = oBuffer.Graphics)
{
//最佳化繪圖輸出
oGraph.CompositingQuality = System.Drawing.Drawing2D.CompositingQuality.HighQuality;
oGraph.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.AntiAlias;
oGraph.PixelOffsetMode = System.Drawing.Drawing2D.PixelOffsetMode.HighQuality;
oGraph.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;
//在目標重繪所屬表單背景色
oGraph.Clear(_oTargetForm.BackColor);
//（匿名函式）運算與繪製父表單背景圖片
System.Action funcDrawBackgroundImage = () => {
int iCorpX; //剪裁座標X
int iCorpY; //剪裁座標Y
int iCorpWidth; //剪裁目標寬
int iCorpHeight; //剪裁目標高
int iPasteTargetX = 0; //黏貼目標座標X
int iPasteTargetY = 0; //黏貼目標座標Y
//評估水平座標系統
if (_oTargetPictureBox.Left < 0)
{
if ((_oTargetPictureBox.Left + _oTargetPictureBox.Width) >= 0) { iCorpX = 0; iCorpWidth = _oTargetPictureBox.Left + _oTargetPictureBox.Width; iPasteTargetX = -(_oTargetPictureBox.Left - 1); }
else { iCorpX = -1; iCorpWidth = -1; }
}
else if (_oTargetPictureBox.Left >= 0 && _oTargetPictureBox.Left < _oTargetForm.BackgroundImage.Width)
{
if ((_oTargetPictureBox.Left + _oTargetPictureBox.Width) < _oTargetForm.BackgroundImage.Width) { iCorpX = _oTargetPictureBox.Left; iCorpWidth = _oTargetPictureBox.Width; iPasteTargetX = 0; }
else { iCorpX = _oTargetPictureBox.Left; iCorpWidth = _oTargetForm.BackgroundImage.Width - _oTargetPictureBox.Left; iPasteTargetX = 0; }
}
else /* means oPB.Left >= this.BackgroundImage.Width */
{
iCorpX = -1; iCorpWidth = -1;
}
//評估垂直座標系統
if (_oTargetPictureBox.Top < 0)
{
if ((_oTargetPictureBox.Top + _oTargetPictureBox.Height) >= 0) { iCorpY = 0; iCorpHeight = _oTargetPictureBox.Top + _oTargetPictureBox.Height; iPasteTargetY = -(_oTargetPictureBox.Top - 1); }
else { iCorpY = -1; iCorpHeight = -1; }
}
else if (_oTargetPictureBox.Top >= 0 && _oTargetPictureBox.Top < _oTargetForm.BackgroundImage.Height)
{
if ((_oTargetPictureBox.Top + _oTargetPictureBox.Height) < _oTargetForm.BackgroundImage.Height) { iCorpY = _oTargetPictureBox.Top; iCorpHeight = _oTargetPictureBox.Height; iPasteTargetY = 0; }
else { iCorpY = _oTargetPictureBox.Top; iCorpHeight = _oTargetForm.BackgroundImage.Height - _oTargetPictureBox.Top; iPasteTargetY = 0; }
}
else /* means oPB.Top >= this.BackgroundImage.Height */
{
iCorpY = -1; iCorpHeight = -1;
}
//評估需不需要填入任何背景
bool bNeedDrawBackgroundImage = true;
if (iCorpX < 0 || iCorpY < 0 || iCorpWidth < 0 || iCorpHeight < 0) { bNeedDrawBackgroundImage = false; }
//如果有需要填入背景，就切割背景影像，貼到應該貼上的位置
if (bNeedDrawBackgroundImage)
{
oGraph.DrawImage(new System.Drawing.Bitmap(
_oTargetForm.BackgroundImage).Clone(
new System.Drawing.Rectangle(iCorpX, iCorpY, iCorpWidth, iCorpHeight),
_oTargetForm.BackgroundImage.PixelFormat
),
new System.Drawing.Point(iPasteTargetX, iPasteTargetY)
);
}
};
//如果表單有背景圖片的話，就重繪背景圖片（透明效果）
if (_oTargetForm.BackgroundImage != null) { funcDrawBackgroundImage(); }
/* 繪製雙圖片輪播效果 */
int iCorpCurrentX = oCurrentImage.Width - _iPartitionPoint;
int iCorpCurrentWidth = oCurrentImage.Width - iCorpCurrentX;
int iCorpNextWidth = iCorpCurrentX;
//丟出事件
if (OnDrawing != null) { OnDrawing(this, new MarqueeImageArgs() { iCurrentImageWidth = iCorpCurrentWidth, iPartitionPoint = _iPartitionPoint, iNextImageWidth = iCorpNextWidth }); }
//繪製現在圖片應該在的位址
if (iCorpCurrentWidth != 0)
{
oGraph.DrawImage(new System.Drawing.Bitmap(
oCurrentImage).Clone(
new System.Drawing.Rectangle(iCorpCurrentX, 0, iCorpCurrentWidth, oCurrentImage.Height),
_oTargetForm.BackgroundImage.PixelFormat
),
new System.Drawing.Point(0, 0)
);
}
//繪製下張圖片應該在的位址
if (iCorpNextWidth != 0)
{
oGraph.DrawImage(new System.Drawing.Bitmap(
oNextImage).Clone(
new System.Drawing.Rectangle(0, 0, iCorpNextWidth, oNextImage.Height),
_oTargetForm.BackgroundImage.PixelFormat
),
new System.Drawing.Point(_iPartitionPoint, 0)
);
}
//計算下一次的位移
if (_iPartitionPoint == 0)
{
_oTimer.Stop();
//修正有時按下螢幕快照截圖時，會產生的繪圖區洗成空白的問題
_oTargetPictureBox.Image = oNextImage;
_oTargetPictureBox.Refresh();
}
else
{
_iPartitionPoint -= iMovePixel;
if (_iPartitionPoint < 0) { _iPartitionPoint = 0; }
}
//將緩衝丟回目標前景
oBuffer.Render(_oTargetPictureBox.CreateGraphics());
}
}
}
/// <summary>
/// 驅動繪圖目標對象使用雙圖形緩衝
/// </summary>
/// <param name="oTemp">套用目標對象</param>
private void SetDoubleBuffering(System.Object oTemp)
{
try
{
//因為SetStyle、UpdateStyles是被設定存取屬性是protected，因此只能透過Reflection來代理
System.Reflection.MethodInfo oMethod_1 = oTemp.GetType().GetMethod("SetStyle", (System.Reflection.BindingFlags.NonPublic | System.Reflection.BindingFlags.Instance));
System.Reflection.MethodInfo oMethod_2 = oTemp.GetType().GetMethod("UpdateStyles", (System.Reflection.BindingFlags.NonPublic | System.Reflection.BindingFlags.Instance));
//如果兩個方法都有調用到，那就Invoke它們
if (oMethod_1 != null && oMethod_2 != null)
{
oMethod_1.Invoke(oTemp, new object[] { System.Windows.Forms.ControlStyles.OptimizedDoubleBuffer, true });
oMethod_2.Invoke(oTemp, new object[] { });
}
}
catch { throw new System.Exception("驅動繪圖對象使用圖形雙重緩衝失敗！"); }
}
}
/// <summary>
/// MarqueeImageArgs參數包
/// </summary>
public class MarqueeImageArgs : System.EventArgs
{
/// <summary>
/// 繪製中前一個圖片的剩餘寬度
/// </summary>
public int iCurrentImageWidth { get; set; }
/// <summary>
/// 分割兩個圖片的座標X軸
/// </summary>
public int iPartitionPoint { get; set; }
/// <summary>
/// 繪製中下一個圖片的當前寬度
/// </summary>
public int iNextImageWidth { get; set; }
}
}
MarqueeImage類別使用方法
使用的方法很簡單，可能你是在Form Load事件下呼叫這個可能被設定成全域物件的oMarquee，然後你只要給他一切應該有的參數後，接著調用.Start();即可。當然，你可以選擇掛上某些額外的按鈕，讓這些按鈕來調用.Stop();方法或者是.OnDrawing()事件。
oMarquee = new MarqueeImage()
{
iPosX = 0,
iPosY = 0,
iWidth = 800,
iHeight = 100,
iTimerInterval = 50,
iMovePixel = 20,
oCurrentImage = System.Drawing.Image.FromFile(@"X:\Slashview\001.png"),
oNextImage = System.Drawing.Image.FromFile(@"X:\Slashview\002.png"),
oTargetForm = this
};
oMarquee.OnDrawing += oMarquee_OnDrawing; //可選擇不掛上事件
oMarquee.Start();
本類別有支援表單（Form）之背景顏色以及背景圖片，因此你可以自由的移動PictureBox到任何表單的可視區域內，類別會自動幫你計算並重新繪製應該繪製的圖片，來產生透明的效果。