压缩图片C#算法

转载自 http://www.open-open.com/lib/view/open1391348644910.html

using System.IO;
using System.Drawing;
using System.Drawing.Imaging;
using System;
namespace Bll
{
    /// <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 ImageHepler
    {
        public Image ResourceImage, ReducedImage;
        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 ImageHepler(string ImageFileName)
        {
            ResourceImage = Image.FromFile(ImageFileName);
            ErrMessage = "";
        }  

        public bool ThumbnailCallback()
        {
            return false;
        }  

        /// <summary>
        /// 生成缩略图，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)
        {
            double LengthLong;          //存储（长和宽中）较短的长度
            int widthOK, heightOK;      //存储实际要生成的图片的长宽
            if (Width < Height)         //判断输入的长和宽那个较短
            {
                LengthLong = Width;     //把较短的存储在 LengthLonh 用于计算
            }
            else
            {
                LengthLong = Height;
            }
            try
            {
                //判断原图片 长和宽
                //原图比较长的一个边要和缩略图的边相等
                if (ResourceImage.Width > ResourceImage.Height)
                {
                    widthOK = (int)LengthLong;
                    heightOK = (int)(LengthLong / ResourceImage.Width * ResourceImage.Height);
                }
                else
                {
                    heightOK = (int)LengthLong;
                    widthOK = (int)LengthLong / ResourceImage.Height * ResourceImage.Width;  

                }
                Image ReducedImage;
                Image.GetThumbnailImageAbort callb = new Image.GetThumbnailImageAbort(ThumbnailCallback);
                ReducedImage = ResourceImage.GetThumbnailImage(widthOK, heightOK, callb, IntPtr.Zero);
                return ReducedImage;
            }
            catch (Exception e)
            {
                ErrMessage = e.Message;
                return null;
            }
        }  

        /// <summary>
        /// 生成缩略图，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)
        {
            double LengthLong;          //存储（长和宽中）较短的长度
            int widthOK, heightOK;      //存储实际要生成的图片的长宽
            if (Width < Height)         //判断输入的长和宽那个较短
            {
                LengthLong = Width;     //把较短的存储在 LengthLonh 用于计算
            }
            else
            {
                LengthLong = Height;
            }
            try
            {
                //判断原图片 长和宽
                //原图比较长的一个边要和缩略图的边相等
                if (ResourceImage.Width > ResourceImage.Height)
                {
                    widthOK = (int)LengthLong;
                    heightOK = (int)(LengthLong / ResourceImage.Width * ResourceImage.Height);
                }
                else
                {
                    heightOK = (int)LengthLong;
                    widthOK = (int)LengthLong / ResourceImage.Height * ResourceImage.Width;
                }
                Image.GetThumbnailImageAbort callb = new Image.GetThumbnailImageAbort(ThumbnailCallback);
                ReducedImage = ResourceImage.GetThumbnailImage(widthOK, heightOK, 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，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，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.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;
            }
        }
    }
}