• c# 无损压缩图片,接口传过来的是字节


        /// <summary>
            /// 无损压缩图片
            /// </summary>
    
            /// <param name="content">base64字节流</param>
            /// <param name="flag">(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 string CompressImage(string content, int flag = 90, int size = 500, bool sfsc = true)
            {
                //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
                byte[] bytes = Convert.FromBase64String(content);
                if (sfsc == true && bytes.Length < size * 1024)
                {
                    return content;
                }
    
                MemoryStream stream = new MemoryStream(bytes, 0, bytes.Length);
                stream.Write(bytes, 0, bytes.Length);
                Image iSource = Image.FromStream(stream);
                ImageFormat tFormat = iSource.RawFormat;
                int dHeight = iSource.Height / 2;
                int dWidth = iSource.Width / 2;
                //按比例缩放
                Size tem_size = new Size(iSource.Width, iSource.Height);
                int sH;
                int sW;
                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 =CompositingQuality.HighQuality;
                g.SmoothingMode = SmoothingMode.HighQuality;
                g.InterpolationMode =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(Encoder.Quality, qy);
                ep.Param[0] = eParam;
                //保存在内存流
                MemoryStream ms = new MemoryStream();
                ms.Position = 0;
                string imagebase64 = "";
                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(ms, jpegICIinfo, ep);
                        byte[] arr = new byte[ms.Length];
                        ms.Read(arr, 0, (int)ms.Length);
                        imagebase64 = Convert.ToBase64String(arr);
                        if (arr.Length > 1024 * size)
                        {
                            flag -= 10;
                            CompressImage(content, flag, size, false);
                        }
                    }
                    else
                    {
                        ob.Save(ms, tFormat);
                        byte[] arr = new byte[ms.Length];
                        ms.Read(arr, 0, (int)ms.Length);
                        imagebase64 = Convert.ToBase64String(bytes);
                     
                    }
                    return imagebase64;
                }
                catch
                {
                    return imagebase64;
                }
                finally
                {
                    iSource.Dispose();
                    ob.Dispose();
                    ms.Close();
                    stream.Close();
                }
    
    
            }
    

      写的不咋地,但是能用了。。嘿

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  • 原文地址:https://www.cnblogs.com/CnnBlog/p/13846172.html
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