PNG in Sprite

Hello,

I’m trying to create an avanced sprite format.
I plan using libPNG & SDL_image for storing multiple PNG images in a single
file, which will have the following format :

[number of frame]
[center offset info for frame 1]
[animation info for frame 1]
[png data for frame 1]
.
.
.
[center offset info for frame n]
[animation info for frame n]
[png data for frame n]

So I checked in SDL_image and I found that SDL_RWFromFP can’t be allocated
from a DLL.
Unfortunatly I though using a thing like this to load a frame :

FILE *rfp;

fread(rfp,…) // offset infos
fread(rfp,…) // animation infos
SDL_RWops rwops=SDL_RWFromFP(rfp,false)
// don’t know the value of false for autoclose, is it 0 ?
IMG_LoadTyped_RW(rwops,0,“PNG”);

Is it correct ?
Will it work ?
This will be part of the Ylib, a high-level C++ library on top of SDL I will
release under LGPL as soon as it becomes a bit cleaner (if anyone is
interested, he can email me, or check at http://ysagoon.com/ylib.html)
Thanks a lot,

Stephane