ASP.NET为图片添加水印功能示例详解

    这两天主要在学习如何给图片添加水印，查找了一下相关的解决方案，其中有一个别人写好的水印dll，虽然能实现很多的功能，但很遗憾不能用于其他商业用途,没办法只能再找找别的办法，后面找到的这种方法比较简单，就是通过Graphics重新绘制bitmap的方法来绘制水印，当然，文字水印可能稍微要麻烦一点儿，需要设置字体相关的东东，比如字号、阴影、颜色啥的，但整体来看，思路基本是一样的。

 

    至于具体的步骤说明，请查看源码上的注释即可，应该能够保证大家不至于太迷糊：

 

    第一部分：水印相关参数结构体和枚举

 

    View Code

 

  1         /// <summary>
  2         /// 水印位置枚举
  3         /// </summary>
  4         public enum ImagePosition
  5         {
  6             LeftTop, //左上 
  7             LeftBottom, //左下 
  8             RightTop, //右上 
  9             RigthBottom, //右下 
 10             TopMiddle, //顶部居中 
 11             BottomMiddle, //底部居中 
 12             Center //中心 
 13         }
 14 
 15         /// <summary>
 16         /// 图片水印参数结构体
 17         /// </summary>
 18         public struct ImageWatermarkParameters
 19         {
 20             /// <summary>
 21             /// 源图片路径
 22             /// </summary>
 23             public string SourceImagePath;
 24             /// <summary>
 25             /// 水印图片路径
 26             /// </summary>
 27             public string WatermarkImagePath;
 28             /// <summary>
 29             /// 源图片数据流（即如果设置数据流，则忽略SourceImagePath属性值）
 30             /// </summary>
 31             public MemoryStream SourceImageStream;
 32             /// <summary>
 33             /// 水印图片数据流（即如果设置数据流，则忽略WatermarkImagePath属性值）
 34             /// </summary>
 35             public MemoryStream WatermarkImageStream;
 36             /// <summary>
 37             /// 透明度，数值介于0.1 - 1.0之间，不包括0.0
 38             /// </summary>
 39             public float Alpha;
 40             /// <summary>
 41             /// 水印位置
 42             /// </summary>
 43             public ImagePosition WmPosition;
 44             private string _sourceImageFileExtensionName;
 45             /// <summary>
 46             /// 源图片文件扩展名
 47             /// </summary>
 48             public string SourceImageFileExtensionName
 49             {
 50                 set { _sourceImageFileExtensionName = value; }
 51                 get
 52                 {
 53                     if (string.IsNullOrEmpty(this.SourceImagePath))
 54                     {
 55                         // 如果设置的图片扩展名为ContentType类型，则进行转化
 56                         if (_sourceImageFileExtensionName.IndexOf("/") > 0)
 57                             _sourceImageFileExtensionName = TransferContentTypeToUnifyExName(_sourceImageFileExtensionName);
 58 
 59                         return _sourceImageFileExtensionName;
 60                     }
 61                     else
 62                         return Path.GetExtension(SourceImagePath).ToLower();
 63                 }
 64             }
 65 
 66 
 67             public ImageWatermarkParameters(string sourceImagePath, string watermarkImagePath, float alpha, ImagePosition wmPosition)
 68             {
 69                 this.SourceImageStream = null;
 70                 this.WatermarkImageStream = null;
 71                 this._sourceImageFileExtensionName = string.Empty;
 72 
 73                 this.SourceImagePath = sourceImagePath;
 74                 this.WatermarkImagePath = watermarkImagePath;
 75                 this.Alpha = alpha;
 76                 this.WmPosition = wmPosition;
 77             }
 78 
 79             public ImageWatermarkParameters(MemoryStream sourceImageStream, MemoryStream watermarkImageStream, 
 80                 string sourceImageFileExtensionName, float alpha, ImagePosition wmPosition)
 81             {
 82                 this.SourceImagePath = string.Empty;
 83                 this.WatermarkImagePath = string.Empty; ;
 84 
 85                 this.SourceImageStream = sourceImageStream;
 86                 this.WatermarkImageStream = watermarkImageStream;
 87                 this.Alpha = alpha;
 88                 this.WmPosition = wmPosition;
 89                 this._sourceImageFileExtensionName = sourceImageFileExtensionName;
 90             }
 91 
 92             /// <summary>
 93             /// 参数检查并设定默认值
 94             /// </summary>
 95             /// <param name="errorMsg"></param>
 96             /// <returns></returns>
 97             public bool CheckAndSetDefault(out string errorMsg)
 98             {
 99                 errorMsg = string.Empty;
100 
101                 // 前置检查
102                 if ((string.IsNullOrEmpty(this.SourceImagePath) && SourceImageStream == null)
103                     || (string.IsNullOrEmpty(this.WatermarkImagePath) && WatermarkImageStream == null)
104                     || (SourceImageStream != null && string.IsNullOrEmpty(_sourceImageFileExtensionName))
105                     || this.Alpha <= 0.0 || this.Alpha > 1.0
106                     || this.WmPosition == null)
107                 {
108                     errorMsg = "文字水印参数实体中含有非法的参数项。";
109                     return false;
110                 }
111 
112                 // 检查图片路径是否合法
113                 if ((SourceImageStream == null && !string.IsNullOrEmpty(this.SourceImagePath) && !File.Exists(this.SourceImagePath)) // 仅赋值源图片路径，且路径不存在的情况
114                     || (WatermarkImageStream == null && !string.IsNullOrEmpty(this.WatermarkImagePath) && !File.Exists(this.WatermarkImagePath))) // 仅赋值水印图片路径，但文件不存在的情况
115                 {
116                     errorMsg = "输入的源图片或水印图片路径不存在。";
117                     return false;
118                 }
119 
120 
121                 // 检查图片扩展名
122                 bool validExName = true;
123                 if (!string.IsNullOrEmpty(this.SourceImagePath) && !string.IsNullOrEmpty(this.WatermarkImagePath))
124                 {
125                     if (!CheckImageExtensionType(this.SourceImagePath) || !CheckImageExtensionType(this.WatermarkImagePath))
126                         validExName = false;
127                 }
128                 else if (this.SourceImageStream != null && this.WatermarkImageStream != null)
129                 {
130                     if ((_sourceImageFileExtensionName != ".gif" && _sourceImageFileExtensionName != ".jpg" && _sourceImageFileExtensionName != ".png"))
131                         validExName = false;
132                 }
133                 else
134                     validExName = false;
135 
136                 if (!validExName)
137                 {
138                     errorMsg = "暂不支持源图片或水印图片的格式类型。";
139                     return false;
140                 }
141 
142                 return true;
143             }
144         }
145 
146         /// <summary>
147         /// 文字水印参数结构体
148         /// </summary>
149         public struct TextWatermarkParameters
150         {
151             /// <summary>
152             /// 源图片路径
153             /// </summary>
154             public string SourceImagePath;
155             /// <summary>
156             /// 水印文字
157             /// </summary>
158             public string WatermarkText;
159             /// <summary>
160             /// 源图片数据流
161             /// </summary>
162             public MemoryStream SourceImageStream;
163             /// <summary>
164             /// 透明度，数值介于0.1 - 1.0之间，不包括0.0
165             /// </summary>
166             public float Alpha;
167             /// <summary>
168             /// 水印位置
169             /// </summary>
170             public ImagePosition WmPosition;
171             /// <summary>
172             /// 水印文字字体样式
173             /// </summary>
174             public Font WmTextFont;
175             /// <summary>
176             /// 水印文字阴影宽度
177             /// </summary>
178             public int TextShadowWidth;
179             private string _sourceImageFileExtensionName;
180             /// <summary>
181             /// 源图片文件扩展名
182             /// </summary>
183             public string SourceImageFileExtensionName
184             {
185                 set { _sourceImageFileExtensionName = value; }
186                 get
187                 {
188                     if (string.IsNullOrEmpty(this.SourceImagePath))
189                     {
190                         // 如果设置的图片扩展名为ContentType类型，则进行转化
191                         if (_sourceImageFileExtensionName.IndexOf("/") > 0)
192                             _sourceImageFileExtensionName = TransferContentTypeToUnifyExName(_sourceImageFileExtensionName);
193 
194                         return _sourceImageFileExtensionName;
195                     }
196                     else
197                         return Path.GetExtension(SourceImagePath).ToLower();
198                 }
199             }
200 
201 
202             public TextWatermarkParameters(MemoryStream sourceImageStream, string sourceImageFileExtensionName, string watermarkText, float alpha, 
203                 ImagePosition wmPosition, Font wmTextFont, int textShadowWidth = 5)
204             {
205                 this.SourceImagePath = string.Empty ;
206 
207                 this.SourceImageStream = sourceImageStream;
208                 this.WatermarkText = watermarkText;
209                 this.Alpha = alpha;
210                 this.WmPosition = wmPosition;
211                 this.WmTextFont = wmTextFont;
212                 this.TextShadowWidth = textShadowWidth;
213                 this._sourceImageFileExtensionName = sourceImageFileExtensionName;
214             }
215 
216             public TextWatermarkParameters(string sourceImagePath, string watermarkText, float alpha,
217                 ImagePosition wmPosition, Font wmTextFont, int textShadowWidth = 5)
218             {
219                 this.SourceImageStream = null;
220                 this._sourceImageFileExtensionName = string.Empty;
221 
222                 this.SourceImagePath = sourceImagePath;
223                 this.WatermarkText = watermarkText;
224                 this.Alpha = alpha;
225                 this.WmPosition = wmPosition;
226                 this.WmTextFont = wmTextFont;
227                 this.TextShadowWidth = textShadowWidth;
228             }
229 
230             /// <summary>
231             /// 参数检查并设定默认值
232             /// </summary>
233             /// <param name="errorMsg"></param>
234             /// <returns></returns>
235             public bool CheckAndSetDefault(out string errorMsg)
236             {
237                 errorMsg = string.Empty;
238 
239                 // 前置检查
240                 if ((string.IsNullOrEmpty(this.SourceImagePath) && this.SourceImageStream == null) || (!string.IsNullOrEmpty(this.SourceImagePath) && !File.Exists(this.SourceImagePath)) 
241                     || string.IsNullOrEmpty(this.WatermarkText)
242                     || (SourceImageStream != null && string.IsNullOrEmpty(_sourceImageFileExtensionName))
243                     || this.Alpha <= 0.0 || this.Alpha > 1.0
244                     || this.WmPosition == null
245                     || this.WmTextFont == null)
246                 {
247                     errorMsg = "文字水印参数实体中含有非法的参数项。";
248                     return false;
249                 }
250 
251                 // 检查图片路径是否合法
252                 if ((SourceImageStream == null && !string.IsNullOrEmpty(this.SourceImagePath) && !File.Exists(this.SourceImagePath))) // 仅赋值源图片路径，且路径不存在的情况
253                 {
254                     errorMsg = "输入的源图片路径不存在。";
255                     return false;
256                 }
257 
258                 // 检查图片扩展名
259                 bool validExName = true;
260                 if (!string.IsNullOrEmpty(this.SourceImagePath))
261                 {
262                     if (!CheckImageExtensionType(this.SourceImagePath))
263                         validExName = false;
264                 }
265                 else if (this.SourceImageStream != null)
266                 {
267                     if ((_sourceImageFileExtensionName != ".gif" && _sourceImageFileExtensionName != ".jpg" && _sourceImageFileExtensionName != ".png"))
268                         validExName = false;
269                 }
270                 else
271                     validExName = false;
272 
273                 if (!validExName)
274                 {
275                     errorMsg = "暂不支持源图片的格式类型。";
276                     return false;
277                 }
278 
279                 return true;
280             }
281

 

    第二部分：水印功能处理类 -> 内部辅助函数部分

 

    View Code

 

return exName;