/** <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(); } }
第二种
4个重载方法,有直接返回Image对象的,有生成缩略图,并且保存到指定目录的!
using System.IO; using System.Drawing; using System.Drawing.Imaging; /// <summary> /// 图片处理类 /// 1、生成缩略图片或按照比例改变图片的大小和画质 /// 2、将生成的缩略图放到指定的目录下 /// </summary> public class ImageClass { public Image ResourceImage; private int ImageWidth; private int ImageHeight; public string ErrMessage; /// <summary> /// 类的构造函数 /// </summary> /// <param name="ImageFileName">图片文件的全路径名称</param> public ImageClass(string ImageFileName) { ResourceImage=Image.FromFile(ImageFileName); ErrMessage=""; } public bool ThumbnailCallback() { return false; } /// <summary> /// 生成缩略图重载方法1，返回缩略图的Image对象 /// </summary> /// <param name="Width">缩略图的宽度</param> /// <param name="Height">缩略图的高度</param> /// <returns>缩略图的Image对象</returns> public Image GetReducedImage(int Width,int Height) { try { Image ReducedImage; Image.GetThumbnailImageAbort callb=new Image.GetThumbnailImageAbort(ThumbnailCallback); ReducedImage=ResourceImage.GetThumbnailImage(Width,Height,callb,IntPtr.Zero); return ReducedImage; } catch(Exception e) { ErrMessage=e.Message; return null; } } /// <summary> /// 生成缩略图重载方法2，将缩略图文件保存到指定的路径 /// </summary> /// <param name="Width">缩略图的宽度</param> /// <param name="Height">缩略图的高度</param> /// <param name="targetFilePath">缩略图保存的全文件名，(带路径)，参数格式：D:\Images\filename.jpg</param> /// <returns>成功返回true，否则返回false</returns> public bool GetReducedImage(int Width,int Height,string targetFilePath) { try { Image ReducedImage; Image.GetThumbnailImageAbort callb=new Image.GetThumbnailImageAbort(ThumbnailCallback); ReducedImage=ResourceImage.GetThumbnailImage(Width,Height,callb,IntPtr.Zero); ReducedImage.Save(@targetFilePath,ImageFormat.Jpeg); ReducedImage.Dispose(); return true; } catch(Exception e) { ErrMessage=e.Message; return false; } } /// <summary> /// 生成缩略图重载方法3，返回缩略图的Image对象 /// </summary> /// <param name="Percent">缩略图的宽度百分比 如：需要百分之80，就填0.8</param> /// <returns>缩略图的Image对象</returns> public Image GetReducedImage(double Percent) { try { Image ReducedImage; Image.GetThumbnailImageAbort callb=new Image.GetThumbnailImageAbort(ThumbnailCallback); ImageWidth=Convert.ToInt32(ResourceImage.Width*Percent); ImageHeight=Convert.ToInt32(ResourceImage.Width*Percent); ReducedImage=ResourceImage.GetThumbnailImage(ImageWidth,ImageHeight,callb,IntPtr.Zero); return ReducedImage; } catch(Exception e) { ErrMessage=e.Message; return null; } } /// <summary> /// 生成缩略图重载方法4，返回缩略图的Image对象 /// </summary> /// <param name="Percent">缩略图的宽度百分比 如：需要百分之80，就填0.8</param> /// <param name="targetFilePath">缩略图保存的全文件名，(带路径)，参数格式：D:\Images\filename.jpg</param> /// <returns>成功返回true,否则返回false</returns> public bool GetReducedImage(double Percent,string targetFilePath) { try { Image ReducedImage; Image.GetThumbnailImageAbort callb=new Image.GetThumbnailImageAbort(ThumbnailCallback); ImageWidth=Convert.ToInt32(ResourceImage.Width*Percent); ImageHeight=Convert.ToInt32(ResourceImage.Width*Percent); ReducedImage=ResourceImage.GetThumbnailImage(ImageWidth,ImageHeight,callb,IntPtr.Zero); ReducedImage.Save(@targetFilePath,ImageFormat.Jpeg); ReducedImage.Dispose(); return true; } catch(Exception e) { ErrMessage=e.Message; return false; } } }