动态在网络图片上写字

1、由于网络安全性，所以不能再网络图片上写字，首先进行图片下载，然后在本地进行写字

具体调用代码如下：

Dictionary<string, string> dic_User = new Dictionary<string, string>();
                dic_User.Add("input", "" + ds.Tables[0].Rows[0]["surname"] + ds.Tables[0].Rows[0]["userName"] + "");//当前接收发证人的姓名
                dic_User.Add("x", "600");
                dic_User.Add("y", "700");
                dic_User.Add("middle", "true");//是否居中显示  true 居中 false 不居中

                Dictionary<string, string> dic_CourseName = new Dictionary<string, string>();
                dic_CourseName.Add("input", "" + ds.Tables[0].Rows[0]["courseName"] + "");//课程名称
                dic_CourseName.Add("x", "600");
                dic_CourseName.Add("y", "900");
                dic_CourseName.Add("middle", "true");//是否居中显示  true 居中 false 不居中

                Dictionary<string, string> dic_Time = new Dictionary<string, string>();
                dic_Time.Add("input", "" + Convert.ToDateTime(ds.Tables[0].Rows[0]["StartTime"]).ToString("yyyy.MM.dd") + "-" + Convert.ToDateTime(ds.Tables[0].Rows[0]["EndTime"]).ToString("yyyy.MM.dd") + "");//证书有效期
                dic_Time.Add("x", "600");
                dic_Time.Add("y", "1200");
                dic_Time.Add("middle", "true");//是否居中显示  true 居中 false 不居中

                Dictionary<string, string> dic_teacher = new Dictionary<string, string>();  //学员讲师
                dic_teacher.Add("input", "" + ds.Tables[0].Rows[0]["teacher"] + "");
                dic_teacher.Add("x", "400");
                dic_teacher.Add("y", "1500");
                dic_teacher.Add("middle", "flase");//是否居中显示  true 居中 false 不居中


                List<Dictionary<string, string>> listdict = new List<Dictionary<string, string>>();
                listdict.Add(dic_User);
                listdict.Add(dic_CourseName);
                listdict.Add(dic_Time);
                listdict.Add(dic_teacher);

                BuildImage.CreateImgage(listdict, Color.Black, ConfigurationManager.AppSettings["examfile"].ToString() + ds.Tables[0].Rows[0]["Url"], tid);

                ImagePrint.ImageUrl = "tempPic/" + tid + ".jpg";

具体实现代码：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Drawing;
using System.Drawing.Imaging;
using System.IO;
using System.Drawing.Drawing2D;
using System.Net;

namespace ELearning.ELearning.Common
{
    /// <summary>
    /// 图片提供程序
    /// create by gaoxing 
    /// 2013-06-09
    /// </summary>
    public static class ImageProvider
    {
        private static BuildImage buildImage = null;

        /// <summary>
        /// 生成图片
        /// create by gaoxing 
        /// 2013-06-09
        /// </summary>
        public static BuildImage Provider
        {
            get
            {
                if (buildImage == null)
                {
                    buildImage = new BuildImage();
                }
                return buildImage;
            }
        }
    }

    public class BuildImage
    {
        private static Matrix m = new Matrix();

        // 定义字体
        private static Font[] fonts = {
                                        new Font(new FontFamily("Times New Roman"), 18, FontStyle.Bold),
                                        new Font(new FontFamily("Georgia"), 18 , FontStyle.Bold),
                                        new Font(new FontFamily("Helvetica"), 18, FontStyle.Bold),
                                        new Font(new FontFamily("Arial"), 18 , FontStyle.Bold)
                                     };

        /// <summary>
        /// 生成图片
        /// create by gaoxing 2013-06-09
        /// </summary>
        /// <param name="str">传入字符串</param>
        /// <param name="bgImg">当前图片对象</param>
        /// <param name="x">X坐标</param>
        /// <param name="y">Y坐标</param>
        /// <param name="color">当前字体颜色</param>
        /// <param name="middle">是否居中显示  true 居中显示  false 不居中显示</param>
        /// <returns></returns>
        private ImageInfo GenerateImage(string str, System.Drawing.Image bgImg, float x, float y, Color color, object middle)
        {



            ImageInfo imageInfo = new ImageInfo();
            imageInfo.ImageFormat = ImageFormat.Jpeg;
            imageInfo.ContentType = "image/pjpeg";

            Bitmap bitmap = new Bitmap(bgImg, bgImg.Width, bgImg.Height);
            Graphics g = Graphics.FromImage(bitmap);
            //是否居中显示
            if (middle != null)
            {
                if (middle.ToString() == "true")
                {
                    //设置X坐标
                    x = SetX(str, x, bitmap, g);
                }
            }

            // 定义前景色 字体颜色
            SolidBrush drawBrush = new SolidBrush(color);

            // 写字
            g.DrawString(str, fonts[3], drawBrush, new PointF(x, y));


            GetStringLength(str, g);


            g.ResetTransform();

            drawBrush.Dispose();
            g.Dispose();
            g.Dispose();

            imageInfo.Image = bitmap;

            return imageInfo;
        }
        /// <summary>
        /// 设置X坐标（居中显示）
        /// create by gaoxing 
        /// </summary>
        /// <param name="str">当前要显示的字符串</param>
        /// <param name="x">X坐标</param>
        /// <param name="bitmap">当前的图片对象</param>
        /// <param name="g">当前的图形对象</param>
        /// <returns>更新后的X</returns>
        private static float SetX(string str, float x, Bitmap bitmap, Graphics g)
        {
            /////////////////////计算字符串的长度/////////////////////////
            Graphics tmpG = g;
            SizeF size = tmpG.MeasureString(str, fonts[3]);
            float length = size.Width;
            //////////////////////////////////////////////
            //计算当前字符串的长度
            //计算当前字符串的起始像素
            float piclength = bitmap.Width;
            x = (piclength / 2) - (length / 2)-25;
            return x;
        }
        /// <summary>
        /// 获取当前字符串的像素长度
        /// create by gaoxing 
        /// </summary>
        /// <param name="str">输入字符串</param>
        /// <param name="g"></param>
        private static float GetStringLength(string str, Graphics g)
        {
            /////////////////////计算字符串的长度/////////////////////////
            Graphics tmpG = g;
            SizeF size = tmpG.MeasureString(str, fonts[3]);
            float StringWidth = size.Width;
            return StringWidth;
            //////////////////////////////////////////////
        }
        /// <summary>
        /// 下载文件
        /// create by 高兴
        /// 2013-06-09
        /// </summary>
        /// <param name="uriString">网络路径地址</param>
        /// <param name="id">当前Id</param>
        /// <returns></returns>
        private static string DownLoadFile(string uriString, string id)
        {
            Uri address = new Uri(uriString);
            string fileName = HttpContext.Current.Server.MapPath("TempPic") + @"" + id + "Model.jpg";
            using (WebClient wc = new WebClient())
            {
                try
                {
                    wc.DownloadFile(address, fileName);
                }
                catch { }
                return fileName;
            }
        }
        /// <summary>
        /// 生成图片，主方法调用
        /// 传入数据集合
        /// 每个字典为一组输入数据
        /// key=input:要打印的字符
        /// key=x X坐标
        /// key=y X坐标
        /// Create by gaoxing
        /// 2013-06-09
        /// </summary>
        /// <param name="listdict">集合数据</param>
        /// <param name="color">当前字体颜色</param>
        /// <param name="ImgUrl">图片网络路径</param>
        /// <param name="imgId">图片Id</param>
        /// <returns></returns>
        public static void CreateImgage(List<Dictionary<string, string>> listdict, Color color, string ImgUrl, string imgId)
        {
            ////更改Http头
            //HttpContext.Current.Response.ClearContent();
            //HttpContext.Current.Response.ContentType = "image/pjpeg";

            //HttpContext.Current.Response.BinaryWrite(BuildImage.GetImage(listdict, color, BuildImage.DownLoadFile(ImgUrl, imgId)).ToArray());
            //HttpContext.Current.Response.End();



            string fileName = HttpContext.Current.Server.MapPath("TempPic") + "/" + imgId + ".jpg";

            using (MemoryStream ms = new MemoryStream(BuildImage.GetImage(listdict, color, BuildImage.DownLoadFile(ImgUrl, imgId)).ToArray()))
            {
                Image image = new Bitmap(ms, true);
                if (File.Exists(fileName))
                {
                    File.Delete(fileName);
                }
                image.Save(fileName);
            }


        }
        /// <summary>
        /// 传入数据集合
        /// 每个字典为一组输入数据
        /// key=input:要打印的字符
        /// key=x X坐标
        /// key=y X坐标
        /// Create by gaoxing
        /// 2013-06-09
        /// </summary>
        /// <param name="listdict">集合数据</param>
        /// <param name="color">当前字体颜色</param>
        /// <param name="imgPath">图片路径</param>
        /// <returns></returns>
        private static MemoryStream GetImage(List<Dictionary<string, string>> listdict, Color color, string imgPath)
        {
            BuildImage buildImage = ImageProvider.Provider;
            ImageInfo imageInfo = new ImageInfo();
            using (MemoryStream ms = new MemoryStream())
            {
                int i = 0;
                foreach (Dictionary<string, string> dic in listdict)
                {
                    if (i < 1)
                    {
                        imageInfo = buildImage.GenerateImage(dic["input"].ToString(), System.Drawing.Image.FromFile(imgPath), float.Parse(dic["x"].ToString()), float.Parse(dic["y"].ToString()), color, dic["middle"].ToString());
                    }
                    else
                    {
                        imageInfo = buildImage.GenerateImage(dic["input"].ToString(), imageInfo.Image, float.Parse(dic["x"].ToString()), float.Parse(dic["y"].ToString()), color, dic["middle"].ToString());
                    }
                    i++;
                }

                long with = System.Drawing.Image.FromFile(imgPath).Width;

                imageInfo.Image.Save(ms, System.Drawing.Imaging.ImageFormat.Jpeg);
                return ms;
            }
        }
    }

    /// <summary>
    /// 图片信息
    /// create by gaoxing 
    /// 2013-06-09
    /// </summary>
    public class ImageInfo
    {
        private Bitmap image;
        private string contentType = "image/pjpeg";
        private ImageFormat imageFormat = ImageFormat.Jpeg;

        /// <summary>
        /// 生成的图片
        /// </summary>
        public Bitmap Image
        {
            get { return image; }
            set { image = value; }
        }

        /// <summary>
        /// 图片类型，如 image/pjpeg
        /// </summary>
        public string ContentType
        {
            get { return contentType; }
            set { contentType = value; }
        }

        /// <summary>
        /// 图片格式
        /// </summary>
        public ImageFormat ImageFormat
        {
            get { return imageFormat; }
            set { imageFormat = value; }
        }
    }
}