imageinterlace() turns the interlace bit on or off.
If the interlace bit is set and the image is used as a JPEG image, the image is created as a progressive JPEG.
image
An image resource, returned by one of the image creation functions, such as imagecreatetruecolor().
interlace
If non-zero, the image will be interlaced, else the interlace bit is turned off.