asp .net实现给图片添加图片水印方法示例

前言

本文主要给大家介绍的是asp .net实现给图片添加图片水印的方法，注意是图片水印，需要的朋友们可以参考学习，下面话不多说来看看详细的介绍吧。

方法如下

首先写好一个写入图片水印的类，先创建一个ImageWriter类库   (该类中有包含枚举类型和方法)

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.IO;
using System.Collections;
using System.Drawing;
using System.Drawing.Drawing2D;
using System.Drawing.Imaging;
namespace ImageWriter
{
 /// <summary>
 /// 图片处理类
 /// </summary>
 public class ImageManager
 {
 #region 变量声明开始
 /// <summary>
 /// 枚举: 水印位置
 /// </summary>
 public enum WatermarkPosition
 {
  /// <summary>
  /// 左上
  /// </summary>
  LeftTop,
  /// <summary>
  /// 左中
  /// </summary>
  Left,
  /// <summary>
  /// 左下
  /// </summary>
  LeftBottom,
  /// <summary>
  /// 正上
  /// </summary>
  Top,
  /// <summary>
  /// 正中
  /// </summary>
  Center,
  /// <summary>
  /// 正下
  /// </summary>
  Bottom,
  /// <summary>
  /// 右上
  /// </summary>
  RightTop,
  /// <summary>
  /// 右中
  /// </summary>
  RightCenter,
  /// <summary>
  /// 右下
  /// </summary>
  RigthBottom
 }
 #endregion 变量声明结束
 #region 构造函数开始
 /// <summary>
 /// 构造函数: 默认
 /// </summary>
 public ImageManager()
 { }
 #endregion 构造函数结束
 #region 私有函数开始
 /// <summary>
 /// 获取: 图片去扩展名(包含完整路径及其文件名)小写字符串
 /// </summary>
 /// <param name="path">图片路径(包含完整路径,文件名及其扩展名): string</param>
 /// <returns>返回: 图片去扩展名(包含完整路径及其文件名)小写字符串: string</returns>
 private string GetFileName(string path)
 {
  return path.Remove(path.LastIndexOf('.')).ToLower();
 }
 /// <summary>
 /// 获取: 图片以'.'开头的小写字符串扩展名
 /// </summary>
 /// <param name="path">图片路径(包含完整路径,文件名及其扩展名): string</param>
 /// <returns>返回: 图片以'.'开头的小写字符串扩展名: string</returns>
 private string GetExtension(string path)
 {
  return path.Remove(0, path.LastIndexOf('.')).ToLower();
 }
 /// <summary>
 /// 获取: 图片以 '.' 开头的小写字符串扩展名对应的 System.Drawing.Imaging.ImageFormat 对象
 /// </summary>
 /// <param name="format">以 '. '开头的小写字符串扩展名: string</param>
 /// <returns>返回: 图片以 '.' 开头的小写字符串扩展名对应的 System.Drawing.Imaging.ImageFormat 对象: System.Drawing.Imaging.ImageFormat</returns>
 private ImageFormat GetImageFormat(string format)
 {
  switch (format)
  {
  case ".bmp":
   return ImageFormat.Bmp;
  case ".emf":
   return ImageFormat.Emf;
  case ".exif":
   return ImageFormat.Exif;
  case ".gif":
   return ImageFormat.Gif;
  case ".ico":
   return ImageFormat.Icon;
  case ".png":
   return ImageFormat.Png;
  case ".tif":
   return ImageFormat.Tiff;
  case ".tiff":
   return ImageFormat.Tiff;
  case ".wmf":
   return ImageFormat.Wmf;
  default:
   return ImageFormat.Jpeg;
  }
 }
 /// <summary>
 /// 获取: 枚举 Uinatlex.ToolBox.ImageManager.WatermarkPosition 对应的 System.Drawing.Rectangle 对象
 /// </summary>
 /// <param name="positon">枚举 Uinatlex.ToolBox.ImageManager.WatermarkPosition: Uinatlex.ToolBox.ImageManager.WatermarkPosition</param>
 /// <param name="X">原图宽度: int</param>
 /// <param name="Y">原图高度: int</param>
 /// <param name="x">水印宽度: int</param>
 /// <param name="y">水印高度: int</param>
 /// <param name="i">边距: int</param>
 /// <returns>返回: 枚举 Uinatlex.ToolBox.ImageManager.WatermarkPosition 对应的 System.Drawing.Rectangle 对象: System.Drawing.Rectangle</returns>
 private Rectangle GetWatermarkRectangle(WatermarkPosition positon, int X, int Y, int x, int y, int i)
 {
  switch (positon)
  {
  case WatermarkPosition.LeftTop:
   return new Rectangle(i, i, x, y);
  case WatermarkPosition.Left:
   return new Rectangle(i, (Y - y) / 2, x, y);
  case WatermarkPosition.LeftBottom:
   return new Rectangle(i, Y - y - i, x, y);
  case WatermarkPosition.Top:
   return new Rectangle((X - x) / 2, i, x, y);
  case WatermarkPosition.Center:
   return new Rectangle((X - x) / 2, (Y - y) / 2, x, y);
  case WatermarkPosition.Bottom:
   return new Rectangle((X - x) / 2, Y - y - i, x, y);
  case WatermarkPosition.RightTop:
   return new Rectangle(X - x - i, i, x, y);
  case WatermarkPosition.RightCenter:
   return new Rectangle(X - x - i, (Y - y) / 2, x, y);
  default:
   return new Rectangle(X - x - i, Y - y - i, x, y);
  }
 }
 #endregion 私有函数结束
 #region 文字生成开始
 #endregion 文字生成结束
 #region 设置透明度开始
 /// <summary>
 /// 设置: 图片 System.Drawing.Bitmap 对象透明度
 /// </summary>
 /// <param name="sBitmap">图片 System.Drawing.Bitmap 对象: System.Drawing.Bitmap</param>
 /// <param name="transparence">水印透明度(值越高透明度越低,范围在0.0f~1.0f之间): float</param>
 /// <returns>图片 System.Drawing.Bitmap: System.Drawing.Bitmap</returns>
 public Bitmap SetTransparence(Bitmap bm, float transparence)
 {
  if (transparence == 0.0f || transparence == 1.0f)
  throw new ArgumentException("透明度值只能在0.0f~1.0f之间");
  float[][] floatArray = 
  {
  new float[] { 1.0f, 0.0f, 0.0f, 0.0f, 0.0f }, 
  new float[] { 0.0f, 1.0f, 0.0f, 0.0f, 0.0f }, 
  new float[] { 0.0f, 0.0f, 1.0f, 0.0f, 0.0f }, 
  new float[] { 0.0f, 0.0f, 0.0f, transparence, 0.0f },
  new float[] { 0.0f, 0.0f, 0.0f, 0.0f, 1.0f } 
  };
  ImageAttributes imageAttributes = new ImageAttributes();
  imageAttributes.SetColorMatrix(new ColorMatrix(floatArray), ColorMatrixFlag.Default, ColorAdjustType.Bitmap);
  Bitmap bitmap = new Bitmap(bm.Width, bm.Height);
  Graphics graphics = Graphics.FromImage(bitmap);
  graphics.DrawImage(bm, new Rectangle(0, 0, bm.Width, bm.Height), 0, 0, bm.Width, bm.Height, GraphicsUnit.Pixel, imageAttributes);
  graphics.Dispose();
  imageAttributes.Dispose();
  bm.Dispose();
  return bitmap;
 }
 /// <summary>
 /// 设置: 图片 System.Drawing.Bitmap 对象透明度
 /// </summary>
 /// <param name="readpath">图片路径(包含完整路径,文件名及其扩展名): string</param>
 /// <param name="transparence">水印透明度(值越高透明度越低,范围在0.0f~1.0f之间): float</param>
 /// <returns>图片 System.Drawing.Bitmap: System.Drawing.Bitmap</returns>
 public Bitmap SetTransparence(string readpath, float transparence)
 {
  return SetTransparence(new Bitmap(readpath), transparence);
 }
 #endregion 设置透明度结束
 #region 添加水印开始
 /// <summary>
 /// 生成: 原图绘制水印的 System.Drawing.Bitmap 对象
 /// </summary>
 /// <param name="sBitmap">原图 System.Drawing.Bitmap 对象: System.Drawing.Bitmap</param>
 /// <param name="wBitmap">水印 System.Drawing.Bitmap 对象: System.Drawing.Bitmap</param>
 /// <param name="position">枚举 Uinatlex.ToolBox.ImageManager.WatermarkPosition : Uinatlex.ToolBox.ImageManager.WatermarkPosition</param>
 /// <param name="margin">水印边距: int</param>
 /// <returns>返回: 原图绘制水印的 System.Drawing.Bitmap 对象 System.Drawing.Bitmap</returns>
 public Bitmap CreateWatermark(Bitmap sBitmap, Bitmap wBitmap, WatermarkPosition position, int margin)
 {
  Graphics graphics = Graphics.FromImage(sBitmap);
  graphics.DrawImage(wBitmap, GetWatermarkRectangle(position, sBitmap.Width, sBitmap.Height, wBitmap.Width, wBitmap.Height, margin));
  graphics.Dispose();
  wBitmap.Dispose();