https://www.cnblogs.com/wdw984/p/13112621.html感謝老哥 我是程式碼搬運工

直接上程式碼

public static class ImageCompress
    {
        /// <summary>
        /// 圖片壓縮
        /// </summary>
        /// <param name="imagePath">圖片檔案路徑</param>
        /// <param name="targetFolder">儲存資料夾</param>
        /// <param name="quality">
 
壓縮質量</param>
        /// <param name="fileSuffix">壓縮後的檔名字尾（防止直接覆蓋原檔案）</param>
        public static void CompressionImage(string imagePath,string targetFolder,long quality = 100,string fileSuffix = "compress")
        {
            if (!File.Exists(imagePath))
            {
                
 
throw new FileNotFoundException();
            }
            if (!Directory.Exists(targetFolder))
            {
                Directory.CreateDirectory(targetFolder);
            }
            var fileInfo = new FileInfo(imagePath);
            var fileName = fileInfo.Name.Replace(fileInfo.Extension,""
 
);
            var fileFullName = Path.Combine($"{targetFolder}",$"{fileName}_{fileSuffix}{fileInfo.Extension}");

            var imageByte = CompressionImage(imagePath,quality);
            var ms = new MemoryStream(imageByte);
            var image = Image.FromStream(ms);
            image.Save(fileFullName);
            ms.Close();
            ms.Dispose();
            image.Dispose();
        }
        private static byte[] CompressionImage(string imagePath,long quality)
        {
            using (var fileStream = new FileStream(imagePath,FileMode.Open))
            {
                using (var img =Image.FromStream(fileStream))
                {
                    using (var bitmap = new Bitmap(img))
                    {
                        var codecInfo = GetEncoder(img.RawFormat);
                        var myEncoder = Encoder.Quality;
                        var myEncoderParameters = new EncoderParameters(1);
                        var myEncoderParameter = new EncoderParameter(myEncoder,quality);
                        myEncoderParameters.Param[0] = myEncoderParameter;
                        using (var ms = new MemoryStream())
                        {
                            bitmap.Save(ms,codecInfo,myEncoderParameters);
                            myEncoderParameters.Dispose();
                            myEncoderParameter.Dispose();
                            return ms.ToArray();
                        }
                    }
                }
            }
        }

        private static ImageCodecInfo GetEncoder(ImageFormat format)
        {
            var codecs = ImageCodecInfo.GetImageDecoders();
            return codecs.FirstOrDefault(codec => codec.FormatID == format.Guid);
        }
    }

呼叫方法（WPF為例）

private void Button_Click(object sender,RoutedEventArgs e)
        {
            var fileDialog = new OpenFileDialog();
            var fileSelect = "";
            if (fileDialog.ShowDialog(this)==true)
            {
                fileSelect = fileDialog.FileName;
            }
            if(string.IsNullOrWhiteSpace(fileSelect)) return;
            
            ImageCompress.CompressionImage(fileSelect,@"d:\",50);

        }