/// 

/// Icon操作类，实现了将Image图像向Icon的转化
/// 
/// 调用示例：
/// Image pic = Image.FromFile(@"D:/tmp/2.png");
/// IconTool.SaveToIcon(pic, @"D:/tmp/test2.ico");
/// 
class IconTool
{
    /// 

    /// Icon图像信息类
    /// 
    public class IconInfo
    {
        public byte Width = 16;         // 图像宽度
        public byte Height = 16;        // 图像高度
        public byte ColorNum = 0;       // 图像中的颜色数
        public byte Reserved = 0;       // 保留字
        public ushort Planes = 1;       // 为目标设备说明位面数
        public ushort PixelBit = 32;    // 每个像素素所占位数

        public uint ImageSize = 0;      // 图像字节大小
        public uint ImageOffset = 0;    // 图形数据起点偏移位置

        public byte[] ImageData;        // 图形数据

        /// 

        /// 创建默认的Icon图像数据结构
        /// 
        public IconInfo() { }
    }

    /// 

    /// 从pic创建Icon信息, 生成Icon的尺寸为rect
    /// 
    public static IconInfo creatIconInfo(Image pic, Rectangle rect)
    {
        int w = pic.Width > 255 ? 255 : pic.Width;
        int h = pic.Height > 255 ? 255 : pic.Height;
        if (rect == Rectangle.Empty || rect.Width > 255 || rect.Height > 255) rect = new Rectangle(0, 0, w, h);

        // 创建最适尺寸的图像
        Bitmap IconBitmap = new Bitmap(rect.Width, rect.Height);
        Graphics g = Graphics.FromImage(IconBitmap);
        g.DrawImage(pic, rect, new Rectangle(0, 0, pic.Width, pic.Height), GraphicsUnit.Pixel);
        g.Dispose();

        // 以位图的形式保存到内存流中
        System.IO.MemoryStream memoryStream = new System.IO.MemoryStream();
        IconBitmap.Save(memoryStream, System.Drawing.Imaging.ImageFormat.Bmp);

        // 从位图创建Icon属性
        IconInfo iconInfo1 = new IconInfo();
        iconInfo1.Width = (byte)rect.Width;
        iconInfo1.Height = (byte)rect.Height;

        // 获取图形数据
        memoryStream.Position = 14;
        iconInfo1.ImageData = new byte[memoryStream.Length - memoryStream.Position];
        memoryStream.Read(iconInfo1.ImageData, 0, iconInfo1.ImageData.Length);

        // Icon图像的高是BMP的2倍
        byte[] Height = BitConverter.GetBytes((uint)iconInfo1.Height * 2);
        iconInfo1.ImageData[8] = Height[0];
        iconInfo1.ImageData[9] = Height[1];
        iconInfo1.ImageData[10] = Height[2];
        iconInfo1.ImageData[11] = Height[3];

        iconInfo1.ImageSize = (uint)iconInfo1.ImageData.Length;
        iconInfo1.ImageOffset = 6 + (uint)(1 * 16);

        return iconInfo1;
    }

    /// 

    /// 保存pic为Icon图像,保存文件路径名称FileName
    /// 
    public static void SaveToIcon(Image pic, string FileName)
    {
        SaveToIcon(pic, Rectangle.Empty, FileName);
    }

    /// 

    /// 保存pic为Icon图像,尺寸rect，保存文件路径名称PathName
    /// 
    public static void SaveToIcon(Image pic, Rectangle rect, string PathName)
    {
        // 获取Icon信息
        IconInfo iconInfo = creatIconInfo(pic, rect);

        // 创建文件输出流，写入文件，生成Icon图像
        System.IO.FileStream stream = new System.IO.FileStream(PathName, System.IO.FileMode.Create);

        // 写入Icon固定部分
        ushort Reserved = 0;
        ushort Type = 1;
        ushort Count = 1;

        byte[] Temp = BitConverter.GetBytes(Reserved);
        stream.Write(Temp, 0, Temp.Length);
        Temp = BitConverter.GetBytes(Type);
        stream.Write(Temp, 0, Temp.Length);
        Temp = BitConverter.GetBytes((ushort)Count);
        stream.Write(Temp, 0, Temp.Length);

        // 写入Icon头信息
        stream.WriteByte(iconInfo.Width);
        stream.WriteByte(iconInfo.Height);
        stream.WriteByte(iconInfo.ColorNum);
        stream.WriteByte(iconInfo.Reserved);
        Temp = BitConverter.GetBytes(iconInfo.Planes);
        stream.Write(Temp, 0, Temp.Length);
        Temp = BitConverter.GetBytes(iconInfo.PixelBit);
        stream.Write(Temp, 0, Temp.Length);
        Temp = BitConverter.GetBytes(iconInfo.ImageSize);
        stream.Write(Temp, 0, Temp.Length);
        Temp = BitConverter.GetBytes(iconInfo.ImageOffset);
        stream.Write(Temp, 0, Temp.Length);

        // 写入图形数据
        stream.Write(iconInfo.ImageData, 0, iconInfo.ImageData.Length);

        stream.Close();
    }
}