C# 实现无损图片压缩技术

 /// <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))
            {