插入图片到RichTextBox

关于插入图片到RichTextBox，在网上找了下资料，大概就两种方法：

①、把图片拷贝到系统剪贴板，再复制到RichTextBox中，最后剪切板内容清空。

②、把图片文件转换成RFT格式，显示到RichTextBox中。

方法一：

很好理解，代码也简单。但是问题在于会改变原来系统剪贴板中内容，所以并不是一个很好实现方式。当然我们可以先备份剪贴板的中的内容，完事后再还原剪贴板内容。尝试了一下，可以实现，代码如下：

public void AddImage(Image img)
        {
            var obj = Clipboard.GetDataObject();

            Clipboard.SetDataObject(img);
            DataFormats.Format format = DataFormats.GetFormat(DataFormats.Bitmap);
            if (this.CanPaste(format))
                this.Paste();

            Clipboard.SetDataObject(obj);

            //this.Rtf = this.InsertImage(img);
        }

方法二：

需要了解RTF格式和图元文件，话说对于这两个东西完全不明白，尝试找RTF指南看看，貌似都是英文。LZ的英文水平太烂，暂时作罢。网上找到代码，贴在这里，得空再研究一下RTF格式和图元文件。

 private enum EmfToWmfBitsFlags
        {
            EmfToWmfBitsFlagsDefault = 0x00000000,
            EmfToWmfBitsFlagsEmbedEmf = 0x00000001,
            EmfToWmfBitsFlagsIncludePlaceable = 0x00000002,
            EmfToWmfBitsFlagsNoXORClip = 0x00000004
        }
        private const int MM_ANISOTROPIC = 8;
        private const int HMM_PER_INCH = 2540;
        private const int TWIPS_PER_INCH = 1440;
        private float xDpi;
        private float yDpi;
        private const string RTF_HEADER = @"{\rtf1\ansi\ansicpg1252\deff0\deflang1033";
        private string RTF_IMAGE_POST = @"}";
   
        /// <summary>
        /// 
        /// </summary>
        /// <param name="_image"></param>
        /// <returns></returns>
        public string InsertImage(Image _image)
        {
            StringBuilder _rtf = new StringBuilder();
            _rtf.Append(RTF_HEADER);
            _rtf.Append(GetImagePrefix(_image));
            _rtf.Append(GetRtfImage(_image));
            _rtf.Append(RTF_IMAGE_POST);
            return _rtf.ToString();
        }

        /// <summary>
        /// 获取图片前缀
        /// </summary>
        /// <param name="_image">图片示例</param>
        /// <returns></returns>
        private string GetImagePrefix(Image _image)
        {
            StringBuilder _rtf = new StringBuilder();
            int picw = (int)Math.Round((_image.Width / xDpi) * HMM_PER_INCH);
            int pich = (int)Math.Round((_image.Height / yDpi) * HMM_PER_INCH);
            int picwgoal = (int)Math.Round((_image.Width / xDpi) * TWIPS_PER_INCH);
            int pichgoal = (int)Math.Round((_image.Height / yDpi) * TWIPS_PER_INCH);
            _rtf.Append(@"{\pict\wmetafile8");
            _rtf.Append(@"\picw");
            _rtf.Append(picw);
            _rtf.Append(@"\pich");
            _rtf.Append(pich);
            _rtf.Append(@"\picwgoal");
            _rtf.Append(picwgoal);
            _rtf.Append(@"\pichgoal");
            _rtf.Append(pichgoal);
            _rtf.Append(" ");
            return _rtf.ToString();
        }

        [DllImportAttribute("gdiplus.dll")]
        private static extern uint GdipEmfToWmfBits(IntPtr _hEmf, uint _bufferSize, byte[] _buffer, int _mappingMode, EmfToWmfBitsFlags _flags);

        /// <summary>
        /// 获取图片二进制格式
        /// </summary>
        /// <param name="_image">图片示例</param>
        /// <returns></returns>
        private string GetRtfImage(Image _image)
        {
            StringBuilder _rtf = null;
            MemoryStream _stream = null;
            Graphics _graphics = null;
            Metafile _metaFile = null;
            IntPtr _hdc;
            try
            {
                _rtf = new StringBuilder();
                _stream = new MemoryStream();
                using (_graphics = this.CreateGraphics())
                {
                    _hdc = _graphics.GetHdc();
                    _metaFile = new Metafile(_stream, _hdc);
                    _graphics.ReleaseHdc(_hdc);
                }
                using (_graphics = Graphics.FromImage(_metaFile))
                {
                    _graphics.DrawImage(_image, new Rectangle(0, 0, _image.Width, _image.Height));

                }
                IntPtr _hEmf = _metaFile.GetHenhmetafile();
                uint _bufferSize = GdipEmfToWmfBits(_hEmf, 0, null, MM_ANISOTROPIC,
                    EmfToWmfBitsFlags.EmfToWmfBitsFlagsDefault);
                byte[] _buffer = new byte[_bufferSize];
                uint _convertedSize = GdipEmfToWmfBits(_hEmf, _bufferSize, _buffer, MM_ANISOTROPIC,
                    EmfToWmfBitsFlags.EmfToWmfBitsFlagsDefault);
                for (int i = 0; i < _buffer.Length; ++i)
                {
                    _rtf.Append(String.Format("{0:X2}", _buffer[i]));
                }

                return _rtf.ToString();
            }
            finally
            {
                if (_graphics != null)
                    _graphics.Dispose();
                if (_metaFile != null)
                    _metaFile.Dispose();
                if (_stream != null)
                    _stream.Close();
            }
        }

    }