Syntax
#define SET_COMP(index,id,hsamp,vsamp,quant,dctbl,actbl) \
(compptr = &cinfo->comp_info[index], \
compptr->component_id = (id), \
compptr->h_samp_factor = (hsamp), \
compptr->v_samp_factor = (vsamp), \
compptr->quant_tbl_no = (quant), \
compptr->dc_tbl_no = (dctbl), \
compptr->ac_tbl_no = (actbl) )