Description
int 
imageinterlace ( resource image [, int interlace] )
     imageinterlace() turns the interlace bit on or off.
     If interlace is 1 the image will be interlaced, and if interlace
     is 0 the interlace bit is turned off.
    
     If the interlace bit is set and the image is used as a JPEG image,
     the image is created as a progressive JPEG.
    
     This function returns whether the interlace bit is set for the
     image.