如何使用 pngquant 使用 php 压缩 ubuntu 服务器上的 jpeg 文件

我正在尝试使用 pngquant 压缩图像（jpeg 和 png），同时上传到我的服务器。我从 pngquant 网站获得的脚本适用于 png 文件，但不适用于 jpeg 文件。我正在使用以下代码（适用于 png 文件）：

function compress_png($path_to_png_file, $max_quality = 90)
{
    if (!file_exists($path_to_png_file)) {
        throw new Exception("File does not exist: $path_to_png_file");
    }
    // guarantee that quality won't be worse than that.
    $min_quality = 60;
    // '-' makes it use stdout, required to save to $compressed_png_content variable
    // '<' makes it read from the given file path
    // escapeshellarg() makes this safe to use with any path
    $compressed_png_content = shell_exec("pngquant --quality=$min_quality-$max_quality - < ".escapeshellarg(    $path_to_png_file));
    if (!$compressed_png_content) {
        throw new Exception("Conversion to compressed PNG failed. Is pngquant 1.8+ installed on the server?");
    }
    return $compressed_png_content;
}
/****************************************************/

$download_url = "https://upload.wikimedia.org/wikipedia/commons/4/47/PNG_transparency_demonstration_1.png";

    // maximum execution time in seconds
    set_time_limit (24 * 60 * 60);
    // folder to save downloaded files to. must end with slash
    $destination_folder = '/IMAGES/';
    $ImageName = "testing_pngquant_image3.png";
    $CompressedImageName = "testing_pngquant_image_compressed3.png";
    $url = $download_url;
    $newfname = $destination_folder . $ImageName;
    $file = fopen ($url, "rb");
    if ($file) {
      $newf = fopen ($newfname, "wb");
      if ($newf)
      while(!feof($file)) {
        fwrite($newf, fread($file, 1024 * 8 ), 1024 * 8 );
      }
    }
    if ($file) {
      fclose($file);
    }
    if ($newf) {
      fclose($newf);
    }

    $path_to_uncompressed_file = $newfname;
    $path_to_compressed_file = $destination_folder . $CompressedImageName;
// this will ensure that $path_to_compressed_file points to compressed file
// and avoid re-compressing if it's been done already
if (!file_exists($path_to_compressed_file)) {
    file_put_contents($path_to_compressed_file, compress_png($path_to_uncompressed_file));
}
// and now, for example, you can output the compressed file:
header("Content-Type: image/png");
header('Content-Length: '.filesize($path_to_compressed_file));
readfile($path_to_compressed_file);
?>

pngquant 可以用于 jpeg 文件吗？或者是否有更好的（免费）工具来压缩 jpeg 文件（如付费的 jpegmini）来使用 php 在我的 ubuntu 服务器上执行此操作。