近期在做相冊功能遇到一个问题，就是载入图片的时候然后放大，感觉有点卡。图片可能有点大，所以考虑用缩略图来实现。

也就是在查询出来一个相冊图片  ，一页显示几十张，这几十张用缩略图来显示，看相信情况的时候想QQ相冊样载入原图放大拉取图片相关信息。所用到的技术就是图片压缩功能。如今功能已经实现看代码。

using System;

using System.Collections.Generic;

using System.ComponentModel;

using System.Data;

using System.Drawing;

using System.Linq;

using System.Text;

using System.Windows.Forms;

using System.Drawing.Imaging;

using System.IO;

namespace WindowsFormsApplication1

{

    public partial class Form1 : Form

    {

        public Form1()

        {

            InitializeComponent();

        }

        private void button1_Click(object sender, EventArgs e)

        {

            string pathPerc = @"D:\0046620140807150650cin.jpg";

            string source = @"G:\0046620140807150650cin.jpg";

            if (!File.Exists(pathPerc))

            {

                File.Create(pathPerc).Close();

            }

            else

            {

                File.Delete(pathPerc);

                File.Create(pathPerc).Close();

            }

            getThumImage(source, 18, 3, pathPerc);

        }

        #region getThumImage

        /**/

        /// <summary>

        /// 生成缩略图

        /// </summary>

        /// <param name="sourceFile">原始图片文件</param>

        /// <param name="quality">质量压缩比</param>

        /// <param name="multiple">收缩倍数</param>

        /// <param name="outputFile">输出文件名称</param>

        /// <returns>成功返回true,失败则返回false</returns>

        public static bool getThumImage(String sourceFile, long quality, int multiple, String outputFile)

        {

            try

            {

                long imageQuality = quality;

                Bitmap sourceImage = new Bitmap(sourceFile);

                ImageCodecInfo myImageCodecInfo = GetEncoderInfo("image/jpeg");

                System.Drawing.Imaging.Encoder myEncoder = System.Drawing.Imaging.Encoder.Quality;

                EncoderParameters myEncoderParameters = new EncoderParameters(1);

                EncoderParameter myEncoderParameter = new EncoderParameter(myEncoder, imageQuality);

                myEncoderParameters.Param[0] = myEncoderParameter;

                float xWidth = sourceImage.Width;

                float yWidth = sourceImage.Height;

                Bitmap newImage = new Bitmap((int)(xWidth / multiple), (int)(yWidth / multiple));

                Graphics g = Graphics.FromImage(newImage);

                g.DrawImage(sourceImage, 0, 0, xWidth / multiple, yWidth / multiple);

                g.Dispose();

                newImage.Save(outputFile, myImageCodecInfo, myEncoderParameters);

                return true;

            }

            catch

            {

                return false;

            }

        }

        #endregion getThumImage

        /**/

        /// <summary>

        /// 获取图片编码信息

        /// </summary>

        private static ImageCodecInfo GetEncoderInfo(String mimeType)

        {

            int j;

            ImageCodecInfo[] encoders;

            encoders = ImageCodecInfo.GetImageEncoders();

            for (j = 0; j < encoders.Length; ++j)

            {

                if (encoders[j].MimeType == mimeType)

                    return encoders[j];

            }

            return null;

        }

    }

}

看下压缩后的图片例如以下

11KB

压缩前的图片

这样缩略图就成功了。