如何生成log新信息背景图片和在图片上添加水印

在图片上添加文字水印，其实就是要用到两个类，

using System.Drawing;
             using System.Drawing.Drawing2D;

废话不多说了，直接上代码；代码很容易看懂；

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Drawing;
using System.Drawing.Drawing2D;
namespace WebApplication10
{
    public enum Postion
    {
        LeftTop,
        RightTop,
        LeftButtom,
        RightButtom,
        Center
    }

    public class Watermark
    {
         public void AddTextToIMage(string IMagePath,string TextStr,Postion postion,string familyfont,float fontSize)
        {
            //设置文字水印的区域
            float RectX = 0;
            float RectY = 0;
            float RectWidth = 0;
            float RectHeight = 0;

            //获取图片
            System.Drawing.Image image = System.Drawing.Image.FromFile(IMagePath);
            System.Drawing.Bitmap bitmap = new System.Drawing.Bitmap(image);
            Graphics g = Graphics.FromImage(bitmap);

            if(fontSize>(float)(image.Height/10.0) || fontSize>(float)(image.Width/10.0))
            {
                fontSize = (fontSize > (float)(image.Height / 10.0)) == true ? (float)(image.Height / 10.0) : (float)(image.Width / 10.0);
            }

            //设置字体
            Font font = new Font(familyfont, fontSize);
            RectWidth = (fontSize + 2) * TextStr.Length;
            RectHeight = fontSize + 4;
            StringFormat strFormat = new StringFormat();
            strFormat.Alignment = StringAlignment.Center;

            //设置画刷
            Color color = Color.FromArgb(221, 221, 221);
            HatchBrush hbbrush = new HatchBrush(HatchStyle.DiagonalCross, color, color);

            switch(postion)
            {
                case Postion.LeftTop:
                    RectX = 0;
                    RectY = 0;
                    break;
                case Postion.LeftButtom:
                    RectX = 0;
                    RectY = image.Height - RectHeight;
                    break;
                case Postion.RightTop:
                    RectX = image.Width - RectWidth;
                    RectY = 0;
                    break;
                case Postion.RightButtom:
                    RectX = image.Width - RectWidth;
                    RectY = image.Height - RectHeight;
                    break;
                case Postion.Center:
                    RectX = (image.Width - RectWidth) / 2;
                    RectY = (image.Height - RectHeight) / 2;
                    break;

            }

            RectangleF rectf = new RectangleF(RectX, RectY, RectWidth, RectHeight);
            g.DrawString(TextStr, font, hbbrush, rectf, strFormat);

            System.IO.MemoryStream ms = new System.IO.MemoryStream();
            bitmap.Save(ms, System.Drawing.Imaging.ImageFormat.Jpeg);

            System.Web.HttpContext.Current.Response.Clear();
            System.Web.HttpContext.Current.Response.ContentType = "image/jpeg";
            System.Web.HttpContext.Current.Response.BinaryWrite(ms.ToArray());

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

        }
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;

namespace WebApplication10
{
    public partial class _default : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {
            Watermark watermark = new Watermark();
            watermark.AddTextToIMage(Server.MapPath("/Images/sss.JPG"), "你好2016！", Postion.Center, "宋体", 15.0f);
        }
    }
}

　结果演示图：