For *.ani, *.sml, *.med, *.big files, each line is in following format:

filename transparent_color colormap_index hotspot_x hotspot_y

Filename is string, all others are int.

filename
	relative to the directory that .ani file is in.

transparent_color
	 -2 : use PNG tRNS chunk transparency specification
	 -1 : transparent color is not used; not transparency in the image
	      (this behavior is enforced, even when tRNS is present)
	  0 : for paletted images, transparent color index 0;
	      special for truecolor images, makes RGB (0,0,0) transparent
	N>0 : for paletted images, transparent color index N;
	      meaningless for truecolor images

colormap_index
	-1 : colormaps are not used for the image
	     for paletted images, the palette from the image itself
	     will be used
	 N : for paletted images, the palette from the colormap N will
	     be used (so some .ct file somewhere defines the palette);
	     meaningless for truecolor images

hotspot_x, hotspot_y
	can both be positive of negative (or 0)
	the position of the image on the screen will be
		(draw_x - hotspot_x, draw_y - hotspot_y)
	so a positive hotspot *usually* defines the logical center of
	an image, and a negative hotspot *usually* defines the position
	of an image within some larger compound image; there are of course
	exceptions to this general rule

This information is parsed in libs/graphics/sdl/3do_getbody.c