C#压缩图片不失真

C#压缩图片不失真

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  • C# 代码   复制
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    using System;
    using System.Collections.Generic;
    using System.Drawing;
    using System.Drawing.Imaging;
    using System.IO;
    using System.Linq;
    using System.Web;
    using System.Web.UI;
    using System.Web.UI.WebControls;
    
    namespace TestProject
    {
        public partial class test : System.Web.UI.Page
        {
            /// <summary>
            /// 无损压缩图片
            /// </summary>
            /// <param name="sFile">原图片地址</param>
            /// <param name="dFile">压缩后保存图片地址</param>
            /// <param name="flag">压缩质量(数字越小压缩率越高)1-100</param>
            /// <param name="size">压缩后图片的最大大小</param>
            /// <param name="sfsc">是否是第一次调用</param>
            /// <returns></returns>
            public static bool CompressImage(string sFile, string dFile, int flag = 90, int size = 300, bool sfsc = true)
            {
                System.Drawing.Image iSource = System.Drawing.Image.FromFile(sFile);
                ImageFormat tFormat = iSource.RawFormat;
                //如果是第一次调用,原始图像的大小小于要压缩的大小,则直接复制文件,并且返回true
                FileInfo firstFileInfo = new FileInfo(sFile);
                if (sfsc == true && firstFileInfo.Length < size * 1024)
                {
                    firstFileInfo.CopyTo(dFile);
                    return true;
                }
    
                int dHeight = iSource.Height / 2;
                int dWidth = iSource.Width / 2;
                int sW = 0, sH = 0;
                //按比例缩放
                Size tem_size = new Size(iSource.Width, iSource.Height);
                if (tem_size.Width > dHeight || tem_size.Width > dWidth)
                {
                    if ((tem_size.Width * dHeight) > (tem_size.Width * dWidth))
                    {
                        sW = dWidth;
                        sH = (dWidth * tem_size.Height) / tem_size.Width;
                    }
                    else
                    {
                        sH = dHeight;
                        sW = (tem_size.Width * dHeight) / tem_size.Height;
                    }
                }
                else
                {
                    sW = tem_size.Width;
                    sH = tem_size.Height;
                }
    
                Bitmap ob = new Bitmap(dWidth, dHeight);
                Graphics g = Graphics.FromImage(ob);
    
                g.Clear(Color.WhiteSmoke);
                g.CompositingQuality = System.Drawing.Drawing2D.CompositingQuality.HighQuality;
                g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;
                g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;
    
                g.DrawImage(iSource, new Rectangle((dWidth - sW) / 2, (dHeight - sH) / 2, sW, sH), 0, 0, iSource.Width, iSource.Height, GraphicsUnit.Pixel);
    
                g.Dispose();
    
                //以下代码为保存图片时,设置压缩质量
                EncoderParameters ep = new EncoderParameters();
                long[] qy = new long[1];
                qy[0] = flag;//设置压缩的比例1-100
                EncoderParameter eParam = new EncoderParameter(System.Drawing.Imaging.Encoder.Quality, qy);
                ep.Param[0] = eParam;
    
                try
                {
                    ImageCodecInfo[] arrayICI = ImageCodecInfo.GetImageEncoders();
                    ImageCodecInfo jpegICIinfo = null;
                    for (int x = 0; x < arrayICI.Length; x++)
                    {
                        if (arrayICI[x].FormatDescription.Equals("JPEG"))
                        {
                            jpegICIinfo = arrayICI[x];
                            break;
                        }
                    }
                    if (jpegICIinfo != null)
                    {
                        ob.Save(dFile, jpegICIinfo, ep);//dFile是压缩后的新路径
                        FileInfo fi = new FileInfo(dFile);
                        if (fi.Length > 1024 * size)
                        {
                            flag = flag - 10;
                            CompressImage(sFile, dFile, flag, size, false);
                        }
                    }
                    else
                    {
                        ob.Save(dFile, tFormat);
                    }
                    return true;
                }
                catch
                {
                    return false;
                }
                finally
                {
                    iSource.Dispose();
                    ob.Dispose();
                }
            }
        }
    }
    
    		
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