C#裁剪,缩放,清晰度,水印处理操作示例

using system;
using system.collections.generic;
using system.text;
using system.io;
using system.drawing;
using system.drawing.drawing2d;
using system.drawing.imaging;

namespace wujian.common
{
 /// <summary>
 /// 图片处理
 /// http://www.cnblogs.com/wu-jian/
 /// 
 /// 吴剑 2011-02-20 创建
 /// 吴剑 2012-08-08 修改
 /// </summary>
 public class image
 {
  #region 正方型裁剪并缩放

  /// <summary>
  /// 正方型裁剪
  /// 以图片中心为轴心，截取正方型，然后等比缩放
  /// 用于头像处理
  /// </summary>
  /// <remarks>吴剑 2012-08-08</remarks>
  /// <param name="fromfile">原图stream对象</param>
  /// <param name="filesaveurl">缩略图存放地址</param>
  /// <param name="side">指定的边长（正方型）</param>
  /// <param name="quality">质量（范围0-100）</param>
  public static void cutforsquare(system.io.stream fromfile, string filesaveurl, int side, int quality)
  {
   //创建目录
   string dir = path.getdirectoryname(filesaveurl);
   if (!directory.exists(dir))
    directory.createdirectory(dir);

   //原始图片（获取原始图片创建对象，并使用流中嵌入的颜色管理信息）
   system.drawing.image initimage = system.drawing.image.fromstream(fromfile, true);

   //原图宽高均小于模版，不作处理，直接保存
   if (initimage.width <= side && initimage.height <= side)
   {
    initimage.save(filesaveurl, system.drawing.imaging.imageformat.jpeg);
   }
   else
   {
    //原始图片的宽、高
    int initwidth = initimage.width;
    int initheight = initimage.height;

    //非正方型先裁剪为正方型
    if (initwidth != initheight)
    {
     //截图对象
     system.drawing.image pickedimage = null;
     system.drawing.graphics pickedg = null;

     //宽大于高的横图
     if (initwidth > initheight)
     {
      //对象实例化
      pickedimage = new system.drawing.bitmap(initheight, initheight);
      pickedg = system.drawing.graphics.fromimage(pickedimage);
      //设置质量
      pickedg.interpolationmode = system.drawing.drawing2d.interpolationmode.highqualitybicubic;
      pickedg.smoothingmode = system.drawing.drawing2d.smoothingmode.highquality;
      //定位
      rectangle fromr = new rectangle((initwidth - initheight) / 2, 0, initheight, initheight);
      rectangle tor = new rectangle(0, 0, initheight, initheight);
      //画图
      pickedg.drawimage(initimage, tor, fromr, system.drawing.graphicsunit.pixel);
      //重置宽
      initwidth = initheight;
     }
     //高大于宽的竖图
     else
     {
      //对象实例化
      pickedimage = new system.drawing.bitmap(initwidth, initwidth);
      pickedg = system.drawing.graphics.fromimage(pickedimage);
      //设置质量
      pickedg.interpolationmode = system.drawing.drawing2d.interpolationmode.highqualitybicubic;
      pickedg.smoothingmode = system.drawing.drawing2d.smoothingmode.highquality;
      //定位
      rectangle fromr = new rectangle(0, (initheight - initwidth) / 2, initwidth, initwidth);
      rectangle tor = new rectangle(0, 0, initwidth, initwidth);
      //画图
      pickedg.drawimage(initimage, tor, fromr, system.drawing.graphicsunit.pixel);
      //重置高
      initheight = initwidth;
     }

     //将截图对象赋给原图
     initimage = (system.drawing.image)pickedimage.clone();
     //释放截图资源
     pickedg.dispose();
     pickedimage.dispose();
    }

    //缩略图对象
    system.drawing.image resultimage = new system.drawing.bitmap(side, side);
    system.drawing.graphics resultg = system.drawing.graphics.fromimage(resultimage);
    //设置质量
    resultg.interpolationmode = system.drawing.drawing2d.interpolationmode.highqualitybicubic;
    resultg.smoothingmode = system.drawing.drawing2d.smoothingmode.highquality;
    //用指定背景色清空画布
    resultg.clear(color.white);
    //绘制缩略图
    resultg.drawimage(initimage, new system.drawing.rectangle(0, 0, side, side), new system.drawing.rectangle(0, 0, initwidth, initheight), system.drawing.graphicsunit.pixel);

    //关键质量控制
    //获取系统编码类型数组,包含了jpeg,bmp,png,gif,tiff
    imagecodecinfo[] icis = imagecodecinfo.getimageencoders();
    imagecodecinfo ici = null;
    foreach (imagecodecinfo i in icis)
    {
     if (i.mimetype == "image/jpeg" || i.mimetype == "image/bmp" || i.mimetype == "image/png" || i.mimetype == "image/gif")
     {
      ici = i;
     }
    }
    encoderparameters ep = new encoderparameters(1);
    ep.param[0] = new encoderparameter(system.drawing.imaging.encoder.quality, (long)quality);

    //保存缩略图
    resultimage.save(filesaveurl, ici, ep);

    //释放关键质量控制所用资源
    ep.dispose();

    //释放缩略图资源
    resultg.dispose();
    resultimage.dispose();

    //释放原始图片资源
    initimage.dispose();
   }
  }

  #endregion

  #region 自定义裁剪并缩放

  /// <summary>
  /// 指定长宽裁剪
  /// 按模版比例最大范围的裁剪图片并缩放至模版尺寸
  /// </summary>
  /// <remarks>吴剑 2012-08-08</remarks>
  /// <param name="fromfile">原图stream对象</param>
  /// <param name="filesaveurl">保存路径</param>
  /// <param name="maxwidth">最大宽(单位:px)</param>
  /// <param name="maxheight">最大高(单位:px)</param>
  /// <param name="quality">质量（范围0-100）</param>
  public static void cutforcustom(system.io.stream fromfile, string filesaveurl, int maxwidth, int maxheight, int quality)
  {
   //从文件获取原始图片，并使用流中嵌入的颜色管理信息
   system.drawing.image initimage = system.drawing.image.fromstream(fromfile, true);

   //原图宽高均小于模版，不作处理，直接保存
   if (initimage.width <= maxwidth && initimage.height <= maxheight)
   {
    initimage.save(filesaveurl, system.drawing.imaging.imageformat.jpeg);
   }
   else
   {
    //模版的宽高比例
    double templaterate = (double)maxwidth / maxheight;
    //原图片的宽高比例
    double initrate = (double)initimage.width / initimage.height;

    //原图与模版比例相等，直接缩放
    if (templaterate == initrate)
    {
     //按模版大小生成最终图片
     system.drawing.image templateimage = new system.drawing.bitmap(maxwidth, maxheight);
     system.drawing.graphics templateg = system.drawing.graphics.fromimage(templateimage);
     templateg.interpolationmode = system.drawing.drawing2d.interpolationmode.high;
     templateg.smoothingmode = system.drawing.drawing2d.smoothingmode.highquality;
     templateg.clear(color.white);
     templateg.drawimage(initimage, new system.drawing.rectangle(0, 0, maxwidth, maxheight), new system.drawing.rectangle(0, 0, initimage.width, initimage.height), system.drawing.graphicsunit.pixel);
     templateimage.save(filesaveurl, system.drawing.imaging.imageformat.jpeg);
    }
    //原图与模版比例不等，裁剪后缩放
    else
    {
     //裁剪对象
     system.drawing.image pickedimage = null;
     system.drawing.graphics pickedg = null;

     //定位
     rectangle fromr = new rectangle(0, 0, 0, 0);//原图裁剪定位
     rectangle tor = new rectangle(0, 0, 0, 0);//目标定位

     //宽为标准进行裁剪
     if (templaterate > initrate)
     {
      //裁剪对象实例化
      pickedimage = new system.drawing.bitmap(initimage.width, (int)system.math.floor(initimage.width / templaterate));
      pickedg = system.drawing.graphics.fromimage(pickedimage);

      //裁剪源定位
      fromr.x = 0;
      fromr.y = (int)system.math.floor((initimage.height - initimage.width / templaterate) / 2);
      fromr.width = initimage.width;
      fromr.height = (int)system.math.floor(initimage.width / templaterate);

      //裁剪目标定位
      tor.x = 0;
      tor.y = 0;
      tor.width = initimage.width;
      tor.height = (int)system.math.floor(initimage.width / templaterate);
     }
     //高为标准进行裁剪
     else
     {
      pickedimage = new system.drawing.bitmap((int)system.math.floor(initimage.height * templaterate), initimage.height);
      pickedg = system.drawing.graphics.fromimage(pickedimage);

      fromr.x = (int)system.math.floor((initimage.width - initimage.height * templaterate) / 2);
      fromr.y = 0;
      fromr.width = (int)system.math.floor(initimage.height * templaterate);
      fromr.height = initimage.height;

      tor.x = 0;
      tor.y = 0;
      tor.width = (int)system.math.floor(initimage.height * templaterate);
      tor.height = initimage.height;
     }

     //设置质量
     pickedg.interpolationmode = system.drawing.drawing2d.interpolationmode.highqualitybicubic;
     pickedg.smoothingmode = system.drawing.drawing2d.smoothingmode.highquality;

     //裁剪
     pickedg.drawimage(initimage, tor, fromr, system.drawing.graphicsunit.pixel);

     //按模版大小生成最终图片
     system.drawing.image templateimage = new system.drawing.bitmap(maxwidth, maxheight);
     system.drawing.graphics templateg = system.drawing.graphics.fromimage(templateimage);
     templateg.interpolationmode = system.drawing.drawing2d.interpolationmode.high;
     templateg.smoothingmode = system.drawing.drawing2d.smoothingmode.highquality;
     templateg.clear(color.white);
     templateg.drawimage(pickedimage, new system.drawing.rectangle(0, 0, maxwidth, maxheight), new system.drawing.rectangle(0, 0, pickedimage.width, pickedimage.height), system.drawing.graphicsunit.pixel);

     //关键质量控制
     //获取系统编码类型数组,包含了jpeg,bmp,png,gif,tiff
     imagecodecinfo[] icis = imagecodecinfo.getimageencoders();
     imagecodecinfo ici = null;
     foreach (imagecodecinfo i in icis)
     {
      if (i.mimetype == "image/jpeg" || i.mimetype == "image/bmp" || i.mimetype == "image/png" || i.mimetype == "image/gif")
      {
       ici = i;
      }
     }
     encoderparameters ep = new encoderparameters(1);
     ep.param[0] = new encoderparameter(system.drawing.imaging.encoder.quality, (long)quality);

     //保存缩略图
     templateimage.save(filesaveurl, ici, ep);
     //templateimage.save(filesaveurl, system.drawing.imaging.imageformat.jpeg);

     //释放资源
     templateg.dispose();
     templateimage.dispose();

     pickedg.dispose();
     pickedimage.dispose();
    }
   }

   //释放资源
   initimage.dispose();
  }
  #endregion

  #region 等比缩放

  /// <summary>
  /// 图片等比缩放
  /// </summary>
  /// <remarks>吴剑 2012-08-08</remarks>
  /// <param name="fromfile">原图stream对象</param>
  /// <param name="savepath">缩略图存放地址</param>
  /// <param name="targetwidth">指定的最大宽度</param>
  /// <param name="targetheight">指定的最大高度</param>
  /// <param name="watermarktext">水印文字(为""表示不使用水印)</param>
  /// <param name="watermarkimage">水印图片路径(为""表示不使用水印)</param>
  public static void zoomauto(system.io.stream fromfile, string savepath, system.double targetwidth, system.double targetheight, string watermarktext, string watermarkimage)
  {
   //创建目录
   string dir = path.getdirectoryname(savepath);
   if (!directory.exists(dir))
    directory.createdirectory(dir);

   //原始图片（获取原始图片创建对象，并使用流中嵌入的颜色管理信息）
   system.drawing.image initimage = system.drawing.image.fromstream(fromfile, true);

   //原图宽高均小于模版，不作处理，直接保存
   if (initimage.width <= targetwidth && initimage.height <= targetheight)
   {
    //文字水印
    if (watermarktext != "")
    {
     using (system.drawing.graphics gwater = system.drawing.graphics.fromimage(initimage))
     {
      system.drawing.font fontwater = new font("黑体", 10);
      system.drawing.brush brushwater = new solidbrush(color.white);
      gwater.drawstring(watermarktext, fontwater, brushwater, 10, 10);
      gwater.dispose();
     }
    }

    //透明图片水印
    if (watermarkimage != "")
    {
     if (file.exists(watermarkimage))
     {
      //获取水印图片
      using (system.drawing.image wrimage = system.drawing.image.fromfile(watermarkimage))
      {
       //水印绘制条件：原始图片宽高均大于或等于水印图片
       if (initimage.width >= wrimage.width && initimage.height >= wrimage.height)
       {
        graphics gwater = graphics.fromimage(initimage);

        //透明属性
        imageattributes imgattributes = new imageattributes();
        colormap colormap = new colormap();
        colormap.oldcolor = color.fromargb(255, 0, 255, 0);
        colormap.newcolor = color.fromargb(0, 0, 0, 0);
        colormap[] remaptable = { colormap };
        imgattributes.setremaptable(remaptable, coloradjusttype.bitmap);

        float[][] colormatrixelements = { 
         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, 0.5f, 0.0f},//透明度:0.5
         new float[] {0.0f, 0.0f, 0.0f, 0.0f, 1.0f}
        };

        colormatrix wmcolormatrix = new colormatrix(colormatrixelements);
        imgattributes.setcolormatrix(wmcolormatrix, colormatrixflag.default, coloradjusttype.bitmap);
        gwater.drawimage(wrimage, new rectangle(initimage.width - wrimage.width, initimage.height - wrimage.height, wrimage.width, wrimage.height), 0, 0, wrimage.width, wrimage.height, graphicsunit.pixel, imgattributes);

        gwater.dispose();
       }
       wrimage.dispose();
      }
     }
    }

    //保存
    initimage.save(savepath, system.drawing.imaging.imageformat.jpeg);
   }
   else
   {
    //缩略图宽、高计算
    double newwidth = initimage.width;
    double newheight = initimage.height;

    //宽大于高或宽等于高（横图或正方）
    if (initimage.width > initimage.height || initimage.width == initimage.height)
    {
     //如果宽大于模版
     if (initimage.width > targetwidth)
     {
      //宽按模版，高按比例缩放
      newwidth = targetwidth;
      newheight = initimage.height * (targetwidth / initimage.width);
     }
    }
    //高大于宽（竖图）
    else
    {
     //如果高大于模版
     if (initimage.height > targetheight)
     {
      //高按模版，宽按比例缩放
      newheight = targetheight;
      newwidth = initimage.width * (targetheight / initimage.height);
     }
    }

    //生成新图
    //新建一个bmp图片
    system.drawing.image newimage = new system.drawing.bitmap((int)newwidth, (int)newheight);
    //新建一个画板
    system.drawing.graphics newg = system.drawing.graphics.fromimage(newimage);

    //设置质量
    newg.interpolationmode = system.drawing.drawing2d.interpolationmode.highqualitybicubic;
    newg.smoothingmode = system.drawing.drawing2d.smoothingmode.highquality;

    //置背景色
    newg.clear(color.white);
    //画图
    newg.drawimage(initimage, new system.drawing.rectangle(0, 0, newimage.width, newimage.height), new system.drawing.rectangle(0, 0, initimage.width, initimage.height), system.drawing.graphicsunit.pixel);

    //文字水印
    if (watermarktext != "")
    {
     using (system.drawing.graphics gwater = system.drawing.graphics.fromimage(newimage))
     {
      system.drawing.font fontwater = new font("宋体", 10);
      system.drawing.brush brushwater = new solidbrush(color.white);
      gwater.drawstring(watermarktext, fontwater, brushwater, 10, 10);
      gwater.dispose();
     }
    }

    //透明图片水印
    if (watermarkimage != "")
    {
     if (file.exists(watermarkimage))
     {
      //获取水印图片
      using (system.drawing.image wrimage = system.drawing.image.fromfile(watermarkimage))
      {
       //水印绘制条件：原始图片宽高均大于或等于水印图片
       if (newimage.width >= wrimage.width && newimage.height >= wrimage.height)
       {
        graphics gwater = graphics.fromimage(newimage);

        //透明属性
        imageattributes imgattributes = new imageattributes();
        colormap colormap = new colormap();
        colormap.oldcolor = color.fromargb(255, 0, 255, 0);
        colormap.newcolor = color.fromargb(0, 0, 0, 0);
        colormap[] remaptable = { colormap };
        imgattributes.setremaptable(remaptable, coloradjusttype.bitmap);

        float[][] colormatrixelements = { 
         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, 0.5f, 0.0f},//透明度:0.5
         new float[] {0.0f, 0.0f, 0.0f, 0.0f, 1.0f}
        };

        colormatrix wmcolormatrix = new colormatrix(colormatrixelements);
        imgattributes.setcolormatrix(wmcolormatrix, colormatrixflag.default, coloradjusttype.bitmap);
        gwater.drawimage(wrimage, new rectangle(newimage.width - wrimage.width, newimage.height - wrimage.height, wrimage.width, wrimage.height), 0, 0, wrimage.width, wrimage.height, graphicsunit.pixel, imgattributes);
        gwater.dispose();
       }
       wrimage.dispose();
      }
     }
    }

    //保存缩略图
    newimage.save(savepath, system.drawing.imaging.imageformat.jpeg);

    //释放资源
    newg.dispose();
    newimage.dispose();
    initimage.dispose();
   }
  }

  #endregion

  #region 其它

  /// <summary>
  /// 判断文件类型是否为web格式图片
  /// (注：jpg,gif,bmp,png)
  /// </summary>
  /// <param name="contenttype">httppostedfile.contenttype</param>
  /// <returns></returns>
  public static bool iswebimage(string contenttype)
  {
   if (contenttype == "image/pjpeg" || contenttype == "image/jpeg" || contenttype == "image/gif" || contenttype == "image/bmp" || contenttype == "image/png")
   {
    return true;
   }
   else
   {
    return false;
   }
  }

  #endregion

 }//end class
}