This section has the list of all of all the public functions added to libpng to support reading and writing animated images.
This function must be called before reading the image data of every frame in a PNG image with an acTl chunk. After calling it, the next frame fcTl will have data for the next frame.
void png_set_progressive_frame_fn(png_structp png_ptr, png_progressive_frame_ptr frame_info_fn, png_progressive_frame_ptr frame_end_fn);
Sets up the function to be called when the info about a frame has been read (just before the frame's pixel data starts).
The callbacks must match this signature:
Eiter of the frame_info_fn and the frame_end_fn paremeters can be NULL.