c#目录以及子目录下图片批量缩放，像素不变，图像大小改变

采用多线程，整体效果

图像根目录黏贴或者手工选择，点击开始，进行目录底下图片筛查。采用多线程，点击开始按钮，开启线程，这样UI不会卡住

private void button2_Click(object sender, EventArgs e)
{
var foldPath = textBox1.Text.Trim();
if (string.IsNullOrEmpty(foldPath))
{
return;
}
ImageZoomThread(foldPath);
}

　　

线程方法：

private void ImageZoomThread(string foldPath)
        {
            ThreadStart threadStart = delegate { listBox1.Items.Clear(); ZoomImage(foldPath); };

            Thread thread = new Thread(threadStart);

            thread.IsBackground = true;

            thread.Start();
        }

　　

缩放图像，核心代码：

 private void ZoomImage(string foldPath)
        {
            DirectoryInfo dir = new DirectoryInfo(foldPath);
            FileInfo[] files = dir.GetFiles("*.jpg");
            DirectoryInfo[] dii = dir.GetDirectories();  

            foreach (var file in files)
            {
                listBox1.Items.Add(file.FullName);
                    listBox1.SelectedIndex = -1;
                    ChangeImageSize(file.FullName, file.FullName.Replace(".jpg", "_zoom.jpg"));
            }

            //获取子文件夹内的文件列表，递归遍历  
            foreach (DirectoryInfo d in dii)
            {
                ZoomImage(d.FullName);
            }  
        }

        /// <summary>
        /// 压缩图片
        /// </summary>
        /// <param name="filePath">要压缩的图片的路径</param>
        /// <param name="newfilePath">压缩后的图片的路径</param>
        public void ChangeImageSize(string filePath, string newfilePath)
        {
            Bitmap bmp = null;
            ImageCodecInfo ici = null;
            System.Drawing.Imaging.Encoder ecd = null;
            EncoderParameter ept = null;
            EncoderParameters eptS = null;
            try
            {
                ici = this.getImageCoderInfo("image/jpeg");
                ecd = System.Drawing.Imaging.Encoder.Quality;
                eptS = new EncoderParameters(1);
                ept = new EncoderParameter(ecd, 35L);
                eptS.Param[0] = ept;
                if (File.Exists(newfilePath))
                {
                    File.Delete(newfilePath);
                }
               bmp = new Bitmap(filePath);
                
                bmp.Save(newfilePath, ici, eptS);
                if (bmp != null)
                    bmp.Dispose();
                ept.Dispose();
                eptS.Dispose();
            }
            catch (Exception ex)
            {
                //throw new Exception(ex.Message);
            }
            finally
            {
                
            }
        }

        /// <summary>
        /// 获取图片编码类型信息
        /// </summary>
        /// <param name="coderType">编码类型</param>
        /// <returns>ImageCodecInfo</returns>
        private ImageCodecInfo getImageCoderInfo(string coderType)
        {
            ImageCodecInfo[] iciS = ImageCodecInfo.GetImageEncoders();
            ImageCodecInfo retIci = null;
            foreach (ImageCodecInfo ici in iciS)
            {
                if (ici.MimeType.Equals(coderType))
                    retIci = ici;
            }
            return retIci;
        }