  We show that the growth curves of galaxies can be used to determine their
bulge and disk parameters and bulge-to-total luminosity ratios, in addition to
their conventional asymptotic magnitudes, provided that the point spread
function is accurately known and signal-to-noise ratio is modest
(S/N$\gtrsim30$). The growth curve is a fundamental quantity that most future
large galaxy imaging surveys will measure. Bulge and disk parameters retrieved
from the growth curve will enable us to perform statistical studies of
luminosity structure for a large number of galaxies.
