gistfile1.txt

              img = Magick::Image.read(folder + "/" + count.to_s).first
              suffix = img.format

identify -list format | grep png
           See http://www.libpng.org/pub/mng/ for details about the JNG
      MNG* PNG       rw+   Multiple-image Network Graphics (libpng 1.2.46)
           See http://www.libpng.org/pub/mng/ for details about the MNG
      PNG* PNG       rw-   Portable Network Graphics (libpng 1.2.46)
           See http://www.libpng.org/ for details about the PNG format.