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C#简单生成缩略图的方法【uwin电竞app官网下载】

文章作者:uwin电竞app官网下载 上传时间:2019-05-20

本文实例讲述了C#简单生成缩略图的方法。分享给大家供大家参考。具体实现方法如下:

本文实例讲述了C#实现为一张大尺寸图片创建缩略图的方法。分享给大家供大家参考。具体实现方法如下:

/// <summary>
/// 生成缩略图
/// </summary>
/// <param name="originalImagePath">源图路径(物理路径)</param>
/// <param name="thumbnailPath">缩略图路径(物理路径)</param>
/// <param name="width">缩略图宽度</param>
/// <param name="height">缩略图高度</param>
/// <param name="mode">生成缩略图的方式</param> 
public static void MakeThumbnail(string originalImagePath, string thumbnailPath, int width, int height, string mode)
{
 Image originalImage = Image.FromFile(originalImagePath);
 int towidth = width;
 int toheight = height;
 int x = 0;
 int y = 0;
 int ow = originalImage.Width;
 int oh = originalImage.Height; 
 switch (mode)
 { 
  case "HW"://指定高宽缩放(可能变形)   
   break;
  case "W"://指定宽,高按比例   
   toheight = originalImage.Height * width/originalImage.Width;
   break;
  case "H"://指定高,宽按比例
   towidth = originalImage.Width * height/originalImage.Height;   
   break; 
  case "Cut"://指定高宽裁减(不变形)   
   if((double)originalImage.Width/(double)originalImage.Height > (double)towidth/(double)toheight)
   {
   oh = originalImage.Height;
   ow = originalImage.Height*towidth/toheight;
   y = 0;
   x = (originalImage.Width - ow)/2;
   }
   else
   {
   ow = originalImage.Width;
   oh = originalImage.Width*height/towidth;
   x = 0;
   y = (originalImage.Height - oh)/2;
   }
   break;   
  default :
   break;
 } 
 //新建一个bmp图片
 Image bitmap = new System.Drawing.Bitmap(towidth,toheight);
 //新建一个画板
 Graphics g = System.Drawing.Graphics.FromImage(bitmap);
 //设置高质量插值法
 g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.High;
 //设置高质量,低速度呈现平滑程度
 g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;
 //清空画布并以透明背景色填充
 g.Clear(Color.Transparent); 
 //在指定位置并且按指定大小绘制原图片的指定部分
 g.DrawImage(originalImage, new Rectangle(0, 0, towidth, toheight),
  new Rectangle(x, y, ow,oh),
  GraphicsUnit.Pixel);
 try
 {  
  //以jpg格式保存缩略图
  bitmap.Save(thumbnailPath, System.Drawing.Imaging.ImageFormat.Jpeg);
 }
 catch(System.Exception e)
 {
  throw e;
 }
 finally
 {
  originalImage.Dispose();
  bitmap.Dispose();    
  g.Dispose();
 }
}
public static Bitmap CreateThumbnail(string lcFilename, int lnWidth, int lnHeight)
{
  System.Drawing.Bitmap bmpOut = null;
  try
  {
    Bitmap loBMP = new Bitmap(lcFilename);
    ImageFormat loFormat = loBMP.RawFormat;
    decimal lnRatio;
    int lnNewWidth = 0;
    int lnNewHeight = 0;
    //*** If the image is smaller than a thumbnail just return it
    if (loBMP.Width < lnWidth && loBMP.Height < lnHeight)
      return loBMP;
    if (loBMP.Width > loBMP.Height)
    {
      lnRatio = (decimal)lnWidth / loBMP.Width;
      lnNewWidth = lnWidth;
      decimal lnTemp = loBMP.Height * lnRatio;
      lnNewHeight = (int)lnTemp;
    }
    else
    {
      lnRatio = (decimal)lnHeight / loBMP.Height;
      lnNewHeight = lnHeight;
      decimal lnTemp = loBMP.Width * lnRatio;
      lnNewWidth = (int)lnTemp;
    }
    bmpOut = new Bitmap(lnNewWidth, lnNewHeight);
    Graphics g = Graphics.FromImage(bmpOut);
    g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;
    g.FillRectangle(Brushes.White, 0, 0, lnNewWidth, lnNewHeight);
    g.DrawImage(loBMP, 0, 0, lnNewWidth, lnNewHeight);
    loBMP.Dispose();
  }
  catch
  {
    return null;
  }
  return bmpOut;
}

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