Value: 1 = to convert the image to a 256 color grayscale JPEG (not used for Gif).
Value: 4 = to convert the image to a 4 bit (16 color) GIF/PNG (not used for JPEG).
Value: 8 = to convert the image to a 8 bit (256 color) GIF/PNG (not used for JPEG).
Value: 24 = to convert the image to a 24 bit (Millions of colors) JPEG (not used for GIF).
Value: 100 = loads the image in its original resolution (4/8 bit will be Gif 24 bit will be Jpeg).
Defaults to 8 when omitted.