C#利用原图和水印图的重叠简单实现水印的方法

本文实例讲述了c#利用原图和水印图的重叠简单实现水印的方法。分享给大家供大家参考，具体如下：

图片操作类

/// <summary>
/// 获取一个图片按等比例缩小后的大小。
/// </summary>
/// <param name="maxwidth">需要缩小到的宽度</param>
/// <param name="maxheight">需要缩小到的高度</param>
/// <param name="imageoriginalwidth">图片的原始宽度</param>
/// <param name="imageoriginalheight">图片的原始高度</param>
/// <returns>返回图片按等比例缩小后的实际大小</returns>
public static size getnewsize(int maxwidth, int maxheight, int imageoriginalwidth, int imageoriginalheight)
{
  double w = 0.0;
  double h = 0.0;
  double sw = convert.todouble(imageoriginalwidth);
  double sh = convert.todouble(imageoriginalheight);
  double mw = convert.todouble(maxwidth);
  double mh = convert.todouble(maxheight);
  if (sw < mw && sh < mh)
  {
    w = sw;
    h = sh;
  }
  else if ((sw / sh) > (mw / mh))
  {
    w = maxwidth;
    h = (w * sh) / sw;
  }
  else
  {
    h = maxheight;
    w = (h * sw) / sh;
  }
  return new size(convert.toint32(w), convert.toint32(h));
}
/// <summary>
/// 对给定的一个图片（image对象）生成一个指定大小的缩略图。
/// </summary>
/// <param name="originalimage">原始图片</param>
/// <param name="thummaxwidth">缩略图的宽度</param>
/// <param name="thummaxheight">缩略图的高度</param>
/// <returns>返回缩略图的image对象</returns>
public static system.drawing.image getthumbnailimage(system.drawing.image originalimage, int thummaxwidth, int thummaxheight)
{
  size thumrealsize = size.empty;
  system.drawing.image newimage = originalimage;
  graphics graphics = null;
  try
  {
    thumrealsize = getnewsize(thummaxwidth, thummaxheight, originalimage.width, originalimage.height);
    newimage = new bitmap(thumrealsize.width, thumrealsize.height);
    graphics = graphics.fromimage(newimage);
    graphics.compositingquality = compositingquality.highquality;
    graphics.interpolationmode = interpolationmode.highqualitybicubic;
    graphics.smoothingmode = smoothingmode.highquality;
    graphics.clear(color.transparent);
    graphics.drawimage(originalimage, new rectangle(0, 0, thumrealsize.width, thumrealsize.height), new rectangle(0, 0, originalimage.width, originalimage.height), graphicsunit.pixel);
  }
  catch { }
  finally
  {
    if (graphics != null)
    {
      graphics.dispose();
      graphics = null;
    }
  }
  return newimage;
}
/// <summary>
/// 对给定的一个图片文件生成一个指定大小的缩略图。
/// </summary>
/// <param name="originalimage">图片的物理文件地址</param>
/// <param name="thummaxwidth">缩略图的宽度</param>
/// <param name="thummaxheight">缩略图的高度</param>
/// <returns>返回缩略图的image对象</returns>
public static system.drawing.image getthumbnailimage(string imagefile, int thummaxwidth, int thummaxheight)
{
  system.drawing.image originalimage = null;
  system.drawing.image newimage = null;
  try
  {
    originalimage = system.drawing.image.fromfile(imagefile);
    newimage = getthumbnailimage(originalimage, thummaxwidth, thummaxheight);
  }
  catch { }
  finally
  {
    if (originalimage != null)
    {
      originalimage.dispose();
      originalimage = null;
    }
  }
  return newimage;
}
/// <summary>
/// 对给定的一个图片文件生成一个指定大小的缩略图，并将缩略图保存到指定位置。
/// </summary>
/// <param name="originalimagefile">图片的物理文件地址</param>
/// <param name="thumbnailimagefile">缩略图的物理文件地址</param>
/// <param name="thummaxwidth">缩略图的宽度</param>
/// <param name="thummaxheight">缩略图的高度</param>
public static void makethumbnail(string originalimagefile, string thumbnailimagefile, int thummaxwidth, int thummaxheight)
{
  system.drawing.image newimage = getthumbnailimage(originalimagefile, thummaxwidth, thummaxheight);
  try
  {
    newimage.save(thumbnailimagefile, imageformat.jpeg);
  }
  catch
  { }
  finally
  {
    newimage.dispose();
    newimage = null;
  }
}
/// <summary>
/// 将一个图片的内存流调整为指定大小，并返回调整后的内存流。
/// </summary>
/// <param name="originalimagestream">原始图片的内存流</param>
/// <param name="newwidth">新图片的宽度</param>
/// <param name="newheight">新图片的高度</param>
/// <returns>返回调整后的图片的内存流</returns>
public static memorystream resizeimage(stream originalimagestream, int newwidth, int newheight)
{
  memorystream newimagestream = null;
  system.drawing.image newimage = globals.getthumbnailimage(system.drawing.image.fromstream(originalimagestream), newwidth, newheight);
  if (newimage != null)
  {
    newimagestream = new memorystream();
    newimage.save(newimagestream, imageformat.jpeg);
  }
  return newimagestream;
}
/// <summary>
/// 将一个内存流保存为磁盘文件。
/// </summary>
/// <param name="stream">内存流</param>
/// <param name="newfile">目标磁盘文件地址</param>
public static void savestreamtofile(stream stream, string newfile)
{
  if (stream == null || stream.length == 0 || string.isnullorempty(newfile))
  {
    return;
  }
  byte[] buffer = new byte[stream.length];
  stream.position = 0;
  stream.read(buffer, 0, buffer.length);
  filestream filestream = new filestream(newfile, filemode.openorcreate, fileaccess.write);
  filestream.write(buffer, 0, buffer.length);
  filestream.flush();
  filestream.close();
  filestream.dispose();
}
/// <summary>
/// 对一个指定的图片加上图片水印效果。
/// </summary>
/// <param name="imagefile">图片文件地址</param>
/// <param name="waterimage">水印图片（image对象）</param>
public static void createimagewatermark(string imagefile, system.drawing.image waterimage)
{
  if (string.isnullorempty(imagefile) || !file.exists(imagefile) || waterimage == null)
  {
    return;
  }
  system.drawing.image originalimage = system.drawing.image.fromfile(imagefile);
  if (originalimage.width - 10 < waterimage.width || originalimage.height - 10 < waterimage.height)
  {
    return;
  }
  graphics graphics = graphics.fromimage(originalimage);
  int x = originalimage.width - waterimage.width - 10;
  int y = originalimage.height - waterimage.height - 10;
  int width = waterimage.width;
  int height = waterimage.height;
  graphics.drawimage(waterimage, new rectangle(x, y, width, height), 0, 0, width, height, graphicsunit.pixel);
  graphics.dispose();
  memorystream stream = new memorystream();
  originalimage.save(stream, imageformat.jpeg);
  originalimage.dispose();
  system.drawing.image imagewithwater = system.drawing.image.fromstream(stream);
  imagewithwater.save(imagefile);
  imagewithwater.dispose();
}
/// <summary>
/// 对一个指定的图片加上文字水印效果。
/// </summary>
/// <param name="imagefile">图片文件地址</param>
/// <param name="watertext">水印文字内容</param>
public static void createtextwatermark(string imagefile, string watertext)
{
  if (string.isnullorempty(imagefile) || string.isnullorempty(watertext) || !file.exists(imagefile))
  {
    return;
  }
  system.drawing.image originalimage = system.drawing.image.fromfile(imagefile);
  graphics graphics = graphics.fromimage(originalimage);
  graphics.smoothingmode = smoothingmode.highquality;
  graphics.textrenderinghint = textrenderinghint.cleartypegridfit;
  graphics.compositingquality = compositingquality.highquality;
  graphics.interpolationmode = interpolationmode.highqualitybicubic;
  solidbrush brush = new solidbrush(color.fromargb(153, 255, 255, 255));
  font watertextfont = new font("arial", 16, fontstyle.regular);
  sizef watertextsize = graphics.measurestring(watertext, watertextfont);
  float x = (float)originalimage.width - watertextsize.width - 10f;
  float y = (float)originalimage.height - watertextsize.height - 10f;
  graphics.drawstring(watertext, watertextfont, brush, x, y);
  graphics.dispose();
  brush.dispose();
  memorystream stream = new memorystream();
  originalimage.save(stream, imageformat.jpeg);
  originalimage.dispose();
  system.drawing.image imagewithwater = system.drawing.image.fromstream(stream);
  imagewithwater.save(imagefile);
  imagewithwater.dispose();
}
/// <summary>
/// 判断上传组件是否包含内容。
/// </summary>
/// <param name="fileupload">asp.net 2.0标准上传组件</param>
/// <returns>如果数据有效，则返回true，否则返回false</returns>
public static bool isattachmentvalid(fileupload fileupload)
{
  if (fileupload != null &&
    fileupload.postedfile != null &&
    !string.isnullorempty(fileupload.postedfile.filename) &&
    fileupload.postedfile.contentlength > 0)
  {
    return true;
  }
  return false;
}

public class imagehelper
{
  #region " 水印存放的相对路径 "
  public static string getlogopath()
  {
    return "/images/logo.png";  ///水印图路径
  }
  #endregion
  #region " 图片水印 "
  // <summary>
  // 在图片上生成图片水印,此方法不支持gif类型的图片
  // </summary>
  // <param name="path">原服务器图片路径</param>
  // <param name="path_syp">生成的带图片水印的图片路径</param>
  // <param name="path_sypf">水印图片路径</param>
  public static void markimage(stream inuploadimagepath, string inlogoimagepath, string insavepath)
  {
    system.drawing.image image = system.drawing.image.fromstream(inuploadimagepath);
    system.drawing.image newimage = image.fromfile(current.server.mappath(inlogoimagepath));
    graphics g = graphics.fromimage(image);
    g.drawimage(newimage, new rectangle(image.width - newimage.width, image.height - newimage.height, newimage.width, newimage.height), 0, 0, newimage.width, newimage.height, graphicsunit.pixel);
    try {
      image.save(current.server.mappath(insavepath));
    }
    catch (exception ex) {
    }
    finally {
      g.dispose();
      image.dispose();
      newimage.dispose();
    }
  }
  #endregion
}

更多关于c#相关内容感兴趣的读者可查看本站专题：《c#图片操作技巧汇总》、《winform控件用法总结》、《c#数据结构与算法教程》、《c#常见控件用法教程》、《c#面向对象程序设计入门教程》及《c#程序设计之线程使用技巧总结》

希望本文所述对大家c#程序设计有所帮助。