1、代码（NPOI v2.3.0）

        /// <summary>
        /// 生成带图片的word文档
        /// </summary>
        /// <param name="paragraphs">段落内容（图片是base64字符串）</param>
        /// <param name="docPath"></param>
        public void CreateDocx(List<string> paragraphs, string docPath = "")
        {
            FileStream fs = null;
            try
            {
                fs = new FileStream(docPath, FileMode.OpenOrCreate, FileAccess.ReadWrite);

                //创建document对象
                var doc = new XWPFDocument();
                foreach (var item in paragraphs)
                {
                    //创建段落对象1
                    var p1 = doc.CreateParagraph();
                    p1.Alignment = ParagraphAlignment.LEFT; //字体左对齐

                    var listItem = GetContainImgArr(item);
                    foreach (var itemTxt in listItem)
                    {

                        if (itemTxt.StartsWith("data:image/")) //处理图片
                        {
                            #region 提取 base64  并转为filestream
                            string base64Str = itemTxt.Substring(itemTxt.IndexOf(',') + 1);
                            string picExtension = itemTxt.Substring(itemTxt.IndexOf('/') + 1, itemTxt.IndexOf(';') - itemTxt.IndexOf('/') - 1);
                            byte[] buff = Convert.FromBase64String(base64Str);
                            MemoryStream mstream = new MemoryStream(buff);
                            #endregion

                            string picName = DateTime.Now.ToString("yyyyMMddHHmmssfff") + "." + picExtension;
                            var runPic = p1.CreateRun();
                            runPic.AddPicture(mstream, GetPictureType(picExtension), picName, 200 * 9525, 200 * 9525);

                            CT_Inline inline = runPic.GetCTR().GetDrawingList()[0].inline[0];
                            inline.docPr.id = 1; //id必须从1开始 解决打开文档时 报错（NPOI v2.4 已修复）

                            mstream.Close();
                        }
                        else
                        {
                            //创建 run对象
                            var runTital = p1.CreateRun();
                            runTital.IsBold = true;
                            runTital.SetText(itemTxt);
                            runTital.FontSize = 16;
                            runTital.SetFontFamily("宋体", FontCharRange.None);
                        }
                    }

                }

                //保存文件
               doc.Write(fs);
            }
            catch (Exception ex)
            {
                throw ex;
            }
            finally
            {
                if (fs != null)
                {
                    fs.Close();
                    fs.Dispose();
                }
            }
        }

        /// <summary>
        ///分隔图片 
        /// </summary>
        /// <param name="str"></param>
        /// <returns></returns>
        public List<string> GetContainImgArr(string str)
        {
            List<string> list = new List<string>();

            var matchArr = Regex.Split(str, "<img src='([^']+?)'>", RegexOptions.IgnoreCase);
            if (matchArr.Length == 0)
            {
                list.Add(str);
                return list;
            }
            else
            {
                list.AddRange(matchArr);
            }
            return list.Where(c => !string.IsNullOrEmpty(c)).ToList();
        }

        /// <summary>
        ///图片类型 
        /// </summary>
        /// <param name="picExtension"></param>
        /// <returns></returns>
        public int GetPictureType(string picExtension)
        {
            switch (picExtension.ToUpper())
            {
                case "EMF":
                    return 2;
                case "WMF":
                    return 3;
                case "PICT":
                    return 4;
                case "JPEG":
                    return 5;
                case "PNG":
                    return 6;
                case "DIB":
                    return 7;
                case "GIF":
                    return 8;
                case "TIFF":
                    return 9;
                case "EPS":
                    return 10;
                case "BMP":
                    return 11;
                case "WPG":
                    return 12;
                default:
                    return 5;
            }

        }

2、 NPOI V2.3.0 word添加图片，打开word文档时报错【v2.4已修复】，解决方法

来源https://github.com/svn2github/npoi/issues/24

image.png

3、处理图片

var matchArr = Regex.Split(str, "<img src='([^']+?)' >", RegexOptions.IgnoreCase);

image.png