The ilutConvertToAlleg function returns an Allegro-compatible version of the current image.

Pal

Allegro palette structure to receive a copy of the palette, if one exists. This may be NULL if no palette exists in the current bound image.

ilutConvertToAlleg makes an Allegro-compatible version of the current bound image and returns it. If a palette exists in the current bound image, Pal is filled with the image's palette.

ILUT_ILLEGAL_OPERATION - There is currently no image bound. Use ilGenImages and ilBindImage before calling this function.
ILUT_OUT_OF_MEMORY - Could not allocate enough memory for the Allegro-compatible image.

ilGenImages, ilBindImage