title: pngquant takes so much time to compress larger images
body: <p>I am using pngquant for image compression with gulp. I have an asset folder with lots of png images. The most images have arround 100kb file size, but there are about two or three images with a file size of about 2MB.</p>
  
  <p>when i start my gulp task using pnquant, every image is compressed immediately apart from the bigger ones. It takes like 10 minutes to compress them completely. Is this normal?</p>
  
  <p>I know that it's okay for bigger files to take longer to compress, but this is just too much, even for that file size.</p>