using System;

using System.Collections.Generic; using System.Text; using System.Drawing;

namespace Common

{ public class ImageMes { /// <summary> /// 生成缩略图 /// </summary> /// <param name="originalImagePath">源图路径</param> /// <param name="thumbnailPath">缩略图路径</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:HW指定高宽缩放(可能变形);W指定宽，高按比例 H指定高，宽按比例 Cut指定高宽裁减(不变形)</param>　　 /// <param name="mode">要缩略图保存的格式(gif,jpg,bmp,png) 为空或未知类型都视为jpg</param>　　 public static void MakeThumbnail(string originalImagePath, string thumbnailPath, int width, int height, string mode, string imageType) { 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 switch (imageType.ToLower()) { case "gif": bitmap.Save(thumbnailPath, System.Drawing.Imaging.ImageFormat.Gif); break; case "jpg": bitmap.Save(thumbnailPath, System.Drawing.Imaging.ImageFormat.Jpeg); break; case "bmp": bitmap.Save(thumbnailPath, System.Drawing.Imaging.ImageFormat.Bmp); break; case "png": bitmap.Save(thumbnailPath, System.Drawing.Imaging.ImageFormat.Png); break; default: bitmap.Save(thumbnailPath, System.Drawing.Imaging.ImageFormat.Jpeg); break; } } catch (System.Exception e) { throw e; } finally { originalImage.Dispose(); bitmap.Dispose(); g.Dispose(); } } } }

本文转自linzheng 51CTO博客，原文链接:http://blog.51cto.com/linzheng/1081742