repetition
Return the number of times to repeat, if this image is animated. This number does not include the first play through of each frame. For example, a repetition count of 4 means that each frame is played 5 times and then the animation stops.
It can return -1, a negative number, meaning that the animation should loop forever.
May require reading the stream to find the repetition count.
As such, future decoding calls may require a rewind.
For still (non-animated) image codecs, this will return 0.