C#图片添加水印的实现代码

using System.Drawing;
using System.Drawing.Imaging;
using System.IO;

namespace HoverTreeBatch.HovercFrame
{
public class HovercWarter
{
public static Image AddTextToImg(Image image, string text)
{
Bitmap bitmap = new Bitmap(image, image.Width, image.Height);
Graphics g = Graphics.FromImage(bitmap);

float fontSize = 12.0f; //字体大小
float textWidth = text.Length * fontSize; //文本的长度
//下面定义一个矩形区域，以后在这个矩形里画上白底黑字
float rectX = 0;
float rectY = 0;
float rectWidth = text.Length * (fontSize + 8);
float rectHeight = fontSize + 8;
//声明矩形域
RectangleF textArea = new RectangleF(rectX, rectY, rectWidth, rectHeight);

Font font = new Font("宋体", fontSize); //定义字体
Brush whiteBrush = new SolidBrush(Color.White); //白笔刷，画文字用
Brush blackBrush = new SolidBrush(Color.Black); //黑笔刷，画背景用

g.FillRectangle(blackBrush, rectX, rectY, rectWidth, rectHeight);

g.DrawString(text, font, whiteBrush, textArea);
MemoryStream ms = new MemoryStream();
//保存为Jpg类型
bitmap.Save(ms, ImageFormat.Jpeg);

Image h_hovercImg = Image.FromStream(ms);

g.Dispose();
bitmap.Dispose();


return h_hovercImg;
}


/// <summary>
/// 根据文件头判断上传的文件类型
/// </summary>
/// <param name="filePath">filePath是文件的完整路径 </param>
/// <returns>返回true或false</returns>
public static bool IsPicture(string filePath)
{
try
{
FileStream fs = new FileStream(filePath, FileMode.Open, FileAccess.Read);
BinaryReader reader = new BinaryReader(fs);
string fileClass;
byte buffer;
buffer = reader.ReadByte();
fileClass = buffer.ToString();
buffer = reader.ReadByte();
fileClass += buffer.ToString();
reader.Close();
fs.Close();
if (fileClass == "255216" || fileClass == "7173" || fileClass == "13780" || fileClass == "6677")
//何问起 hovertree.com
//255216是jpg;7173是gif;6677是BMP,13780是PNG;7790是exe,8297是rar 
{
return true;
}
else
{
return false;
}
}
catch
{
return false;
}
}
}
}