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[ASP.net教程]利用System.Drawing.Image类进行图片相关操作


    C#中对图片的操作主要是通过System.Drawing.Image等类进行。

    一、将图片转换为字节流

  /// <summary>  /// 图片处理帮助类  /// </summary>  public static class PicProcessHelper  {    /// <summary>    /// 将图片转换为指定的字节流    /// </summary>    /// <param name="filePath">图片路径</param>    /// <returns>指定的字节流</returns>    public static byte[] ConvertToByte(String filePath)    {      var m = new System.IO.MemoryStream();      var bp = new System.Drawing.Bitmap(filePath);      bp.Save(m, System.Drawing.Imaging.ImageFormat.Jpeg); //将此图像以指定的格式保存到指定的流中。      byte[] imgByte = m.GetBuffer(); //从内存缓冲区中读取      return imgByte;    }  }

    二、将字节流转换回图片

    /// <summary>    /// 根据字节流返回Image类型    /// </summary>    /// <param name="streamByte"></param>    /// <returns></returns>    public static Image ReturnImage(byte[] streamByte)    {      System.IO.MemoryStream ms = new System.IO.MemoryStream(streamByte);      Image img = Image.FromStream(ms);      return img;    }

    三、将Image对象转换为字节流

    //将Image转换成流数据,并保存为byte[]      public static byte[] PhotoImageInsert(System.Drawing.Image imgPhoto)    {      MemoryStream mstream = new MemoryStream();      imgPhoto.Save(mstream, System.Drawing.Imaging.ImageFormat.Bmp);      byte[] byData = new Byte[mstream.Length];      mstream.Position = 0;      mstream.Read(byData, 0, byData.Length); mstream.Close();      return byData;    }

    四、保存图片

      var oldFilename = @"E:\环境部署\图片集\熊猫1.jpg";      var oldImage = System.Drawing.Image.FromFile(oldFilename);      var newFilename = @"E:\我的新熊猫.jpg";      oldImage.Save(newFilename, ImageFormat.Jpeg);

    五、生成缩略图

 1     /// <summary>  2     /// 生成图片缩略文件  3     /// </summary>  4     /// <param name="originalImage">图片源文件</param>  5     /// <param name="width">缩略图宽度</param>  6     /// <param name="height">缩略图高度</param>  7     /// <param name="mode">生成缩略图的方式</param>  8     /// <returns>缩率处理后图片文件</returns>  9     public static Image MakeThumbnail(Image originalImage, int width, int height, ThumbnailModel mode) 10     { 11       int towidth = width; 12       int toheight = height; 13  14       int x = 0; 15       int y = 0; 16       int ow = originalImage.Width; 17       int oh = originalImage.Height; 18  19       switch (mode) 20       { 21         case ThumbnailModel.HighWidth: //指定高宽缩放(可能变形)   22           break; 23         case ThumbnailModel.Width: //指定宽,高按比例   24           toheight = originalImage.Height * width / originalImage.Width; 25           break; 26         case ThumbnailModel.Hight: //指定高,宽按比例  27           towidth = originalImage.Width * height / originalImage.Height; 28           break; 29         case ThumbnailModel.Default: //指定高,宽按比例  30           if (ow <= towidth && oh <= toheight) 31           { 32             x = -(towidth - ow) / 2; 33             y = -(toheight - oh) / 2; 34             ow = towidth; 35             oh = toheight; 36           } 37           else 38           { 39             if (ow > oh)//宽大于高 40             { 41               x = 0; 42               y = -(ow - oh) / 2; 43               oh = ow; 44             } 45             else//高大于宽 46             { 47               y = 0; 48               x = -(oh - ow) / 2; 49               ow = oh; 50             } 51           } 52           break; 53         case ThumbnailModel.Auto: 54           if (originalImage.Width / originalImage.Height >= width / height) 55           { 56             if (originalImage.Width > width) 57             { 58               towidth = width; 59               toheight = (originalImage.Height * width) / originalImage.Width; 60             } 61             else 62             { 63               towidth = originalImage.Width; 64               toheight = originalImage.Height; 65             } 66           } 67           else 68           { 69             if (originalImage.Height > height) 70             { 71               toheight = height; 72               towidth = (originalImage.Width * height) / originalImage.Height; 73             } 74             else 75             { 76               towidth = originalImage.Width; 77               toheight = originalImage.Height; 78             } 79           } 80           break; 81         case ThumbnailModel.Cut: //指定高宽裁减(不变形)   82           if ((double)originalImage.Width / (double)originalImage.Height > (double)towidth / (double)toheight) 83           { 84             oh = originalImage.Height; 85             ow = originalImage.Height * towidth / toheight; 86             y = 0; 87             x = (originalImage.Width - ow) / 2; 88           } 89           else 90           { 91             ow = originalImage.Width; 92             oh = originalImage.Width * height / towidth; 93             x = 0; 94             y = (originalImage.Height - oh) / 2; 95           } 96           break; 97         default: 98  99           break;100       }101 102       //新建一个bmp图片 103       System.Drawing.Image bitmap = new System.Drawing.Bitmap(towidth, toheight);104 105       //新建一个画板 106       System.Drawing.Graphics g = System.Drawing.Graphics.FromImage(bitmap);107 108       //设置高质量插值法 109       g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.High;110 111       //设置高质量,低速度呈现平滑程度 112       g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;113 114       //清空画布并以透明背景色填充 115       g.Clear(System.Drawing.Color.White);116 117       //在指定位置并且按指定大小绘制原图片的指定部分 118       g.DrawImage(originalImage, new System.Drawing.Rectangle(0, 0, towidth, toheight),119             new System.Drawing.Rectangle(x, y, ow, oh),120             System.Drawing.GraphicsUnit.Pixel);121 122       return bitmap;123     }

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    其中缩略图模式定义如下:

  /// <summary>  /// 缩率图处理模式  /// </summary>  public enum ThumbnailModel  {    /// <summary>    /// 指定高宽缩放(可能变形)      /// </summary>    HighWidth,    /// <summary>    /// 指定宽,高按比例      /// </summary>    Width,    /// <summary>    /// 默认 全图不变形      /// </summary>    Default,    /// <summary>    /// 指定高,宽按比例    /// </summary>    Hight,    /// <summary>    /// 指定高宽裁减(不变形)??指定裁剪区域    /// </summary>    Cut,    /// <summary>    /// 自动 原始图片按比例缩放    /// </summary>    Auto  }

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