.NET图片压缩和生成缩略图

当 图片的质量没有处理的时候，一样的宽高的图片大小却错10倍，在网站中考虑到 速度还是压缩下图片的质量；吧
类：转类，添加了个压缩图片功能

using System;using System.Collections.Generic;using System.Web;using System.Drawing.Imaging;using System.Drawing;/// <SUMMARY>///MakeThum 的摘要说明/// </SUMMARY>public class MakeThum{    public MakeThum()    {        //        //TODO: 在此处添加构造函数逻辑        //    }    /// <SUMMARY>    /// 生成缩略图//带压缩图片不压缩22k压缩2k    /// </SUMMARY>    /// <PARAM name="originalImagePath" />原始路径    /// <PARAM name="thumbnailPath" />生成缩略图路径    /// <PARAM name="width" />缩略图的宽    /// <PARAM name="height" />缩略图的高    //是否压缩图片质量    public void MakeThumbnail(string originalImagePath, string thumbnailPath, int width, int height, bool Ys)    {        //获取原始图片          System.Drawing.Image originalImage = System.Drawing.Image.FromFile(originalImagePath);        //缩略图画布宽高          int towidth = width;        int toheight = height;        //原始图片写入画布坐标和宽高(用来设置裁减溢出部分)          int x = 0;        int y = 0;        int ow = originalImage.Width;        int oh = originalImage.Height;        //原始图片画布,设置写入缩略图画布坐标和宽高(用来原始图片整体宽高缩放)          int bg_x = 0;        int bg_y = 0;        int bg_w = towidth;        int bg_h = toheight;        //倍数变量          double multiple = 0;        //获取宽长的或是高长与缩略图的倍数          if (originalImage.Width >= originalImage.Height)            multiple = (double)originalImage.Width / (double)width;        else            multiple = (double)originalImage.Height / (double)height;        //上传的图片的宽和高小等于缩略图          if (ow <= width && oh <= height)        {            //缩略图按原始宽高              bg_w = originalImage.Width;            bg_h = originalImage.Height;            //空白部分用背景色填充              bg_x = Convert.ToInt32(((double)towidth - (double)ow) / 2);            bg_y = Convert.ToInt32(((double)toheight - (double)oh) / 2);        }        //上传的图片的宽和高大于缩略图          else        {            //宽高按比例缩放              bg_w = Convert.ToInt32((double)originalImage.Width / multiple);            bg_h = Convert.ToInt32((double)originalImage.Height / multiple);            //空白部分用背景色填充              bg_y = Convert.ToInt32(((double)height - (double)bg_h) / 2);            bg_x = Convert.ToInt32(((double)width - (double)bg_w) / 2);        }        //新建一个bmp图片,并设置缩略图大小.          System.Drawing.Image bitmap = new System.Drawing.Bitmap(towidth, toheight);        //新建一个画板          System.Drawing.Graphics g = System.Drawing.Graphics.FromImage(bitmap);        //设置高质量插值法          g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBilinear;        //设置高质量,低速度呈现平滑程度          g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;        //清空画布并设置背景色          g.Clear(System.Drawing.ColorTranslator.FromHtml("#FFF"));        //在指定位置并且按指定大小绘制原图片的指定部分          //第一个System.Drawing.Rectangle是原图片的画布坐标和宽高,第二个是原图片写在画布上的坐标和宽高,最后一个参数是指定数值单位为像素          g.DrawImage(originalImage, new System.Drawing.Rectangle(bg_x, bg_y, bg_w, bg_h), new System.Drawing.Rectangle(x, y, ow, oh), System.Drawing.GraphicsUnit.Pixel);        if (Ys)        {            System.Drawing.Imaging.ImageCodecInfo encoder = GetEncoderInfo("image/jpeg");            try            {                if (encoder != null)                {                    System.Drawing.Imaging.EncoderParameters encoderParams = new System.Drawing.Imaging.EncoderParameters(1);                    //设置 jpeg 质量为 60                    encoderParams.Param[0] = new System.Drawing.Imaging.EncoderParameter(System.Drawing.Imaging.Encoder.Quality, (long)60);                    bitmap.Save(thumbnailPath, encoder, encoderParams);                    encoderParams.Dispose();                }            }            catch (System.Exception e)            {                throw e;            }            finally            {                originalImage.Dispose();                bitmap.Dispose();                g.Dispose();            }        }        else        {            try            {                //获取图片类型                  string fileExtension = System.IO.Path.GetExtension(originalImagePath).ToLower();                //按原图片类型保存缩略图片,不按原格式图片会出现模糊,锯齿等问题.                  switch (fileExtension)                {                    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;                }            }            catch (System.Exception e)            {                throw e;            }            finally            {                originalImage.Dispose();                bitmap.Dispose();                g.Dispose();            }        }    }    private System.Drawing.Imaging.ImageCodecInfo GetEncoderInfo(string mimeType)    {        //根据 mime 类型，返回编码器        System.Drawing.Imaging.ImageCodecInfo result = null;        System.Drawing.Imaging.ImageCodecInfo[] encoders = System.Drawing.Imaging.ImageCodecInfo.GetImageEncoders();        for (int i = 0; i < encoders.Length; i++)        {            if (encoders[i].MimeType == mimeType)            {                result = encoders[i];                break;            }        }        return result;    }}