方法1：利用Windows窗體的TransparencyKey屬性實現
優點：簡單，無需編碼； 缺點：如果用戶顯示器分辨率在24位以上會出問題
步驟：將Form的BackgroundImage屬性指定爲要顯示的位圖；對TransparencyKey屬性指定要隱藏的顏色
方法2：利用編程方式實現
優點：無論顯示器分辨率是多少，都不會出問題； 缺點：編程複雜
步驟1：新建一窗體，然後在load事件裏面寫代碼
private void Form2_Load(object sender, EventArgs e)
{ Bitmap b = new Bitmap("../../Resources/backPic.bmp");
BitmapRegion.CreateControlRegion(this, b); //此爲生成不規則窗體和控件的類 }步驟2：新建一個類文件BitmapRegion.cs，然後寫入下列的代碼
using System;using System.Drawing;using System.Drawing.Drawing2D;using System.Windows.Forms; namespace IrregularForm{ public class BitmapRegion
{
public BitmapRegion() { } /// <summary> /// Create and apply the region on the supplied control /// 創建支持位圖區域的控件（目前有button和form） /// </summary> /// <param name="control">The Control object to apply the region to控件</param> 
/// <param name="bitmap">The Bitmap object to create the region from位圖</param> public static void CreateControlRegion(Control control, Bitmap bitmap) { // Return if control and bitmap are null //判斷是否存在控件和位圖 if (control == null || bitmap == null) return; // Set our control''s size to be the same as the bitmap //設置控件大小爲位圖大小 control.Width = bitmap.Width; control.Height = bitmap.Height; // Check if we are dealing with Form here //當控件是form時 if (control is System.Windows.Forms.Form) { // Cast to a Form object //強制轉換爲FORM Form form = (Form)control; // Set our form''s size to be a little larger that the bitmap just // in case the form''s border style is not set to none in the first place //當FORM的邊界FormBorderStyle不爲NONE時，應將FORM的大小設置成比位圖大小稍大一點 form.Width = control.Width; form.Height = control.Height; // No border //沒有邊界 form.FormBorderStyle = FormBorderStyle.None; // Set bitmap as the background image //將位圖設置成窗體背景圖片 form.BackgroundImage = bitmap; // Calculate the graphics path based on the bitmap supplied //計算位圖中不透明部分的邊界 GraphicsPath graphicsPath = CalculateControlGraphicsPath(bitmap); // Apply new region //應用新的區域 form.Region = new Region(graphicsPath); } // Check if we are dealing with Button here //當控件是button時 else if (control is System.Windows.Forms.Button) { // Cast to a button object //強制轉換爲 button Button button = (Button)control; // Do not show button text //不顯示button text button.Text = ""; // Change cursor to hand when over button //改變 cursor的style button.Cursor = Cursors.Hand; // Set background image of button //設置button的背景圖片 button.BackgroundImage = bitmap; // Calculate the graphics path based on the bitmap supplied //計算位圖中不透明部分的邊界 GraphicsPath graphicsPath = CalculateControlGraphicsPath(bitmap); // Apply new region //應用新的區域 button.Region = new Region(graphicsPath); } } /// <summary> /// Calculate the graphics path that representing the figure in the bitmap /// excluding the transparent color which is the top left pixel. /// //計算位圖中不透明部分的邊界 /// </summary> /// <param name="bitmap">The Bitmap object to calculate our graphics path from</param> /// <returns>Calculated graphics path</returns> private static GraphicsPath CalculateControlGraphicsPath(Bitmap bitmap) { // Create GraphicsPath for our bitmap calculation //創建 GraphicsPath GraphicsPath graphicsPath = new GraphicsPath(); // Use the top left pixel as our transparent color //使用左上角的一點的顏色作爲我們透明色 Color colorTransparent = bitmap.GetPixel(0, 0); // This is to store the column value where an opaque pixel is first found. // This value will determine where we start scanning for trailing opaque pixels. //第一個找到點的X int colOpaquePixel = 0; // Go through all rows (Y axis) // 偏歷所有行（Y方向） for (int row = 0; row < bitmap.Height; row++) { // Reset value //重設 colOpaquePixel = 0; // Go through all columns (X axis) //偏歷所有列（X方向） for (int col = 0; col < bitmap.Width; col++) { // If this is an opaque pixel, mark it and search for anymore trailing behind //如果是不需要透明處理的點則標記，然後繼續偏歷 if (bitmap.GetPixel(col, row) != colorTransparent) { // Opaque pixel found, mark current position //記錄當前 colOpaquePixel = col; // Create another variable to set the current pixel position //建立新變量來記錄當前點 int colNext = col; // Starting from current found opaque pixel, search for anymore opaque pixels // trailing behind, until a transparent pixel is found or minimum width is reached ///從找到的不透明點開始，繼續尋找不透明點,一直到找到或則達到圖片寬度 for (colNext = colOpaquePixel; colNext < bitmap.Width; colNext++) if (bitmap.GetPixel(colNext, row) == colorTransparent) break; // Form a rectangle for line of opaque pixels found and add it to our graphics path //將不透明點加到graphics path graphicsPath.AddRectangle(new Rectangle(colOpaquePixel, row, colNext - colOpaquePixel, 1)); // No need to scan the line of opaque pixels just found col = colNext; } } } // Return calculated graphics path return graphicsPath; } } 
}