  This paper presents large scale extinction maps of most nearby Giant
Molecular Clouds of the Galaxy (Lupus, rho-Ophiuchus, Scorpius, Coalsack,
Taurus, Chamaeleon, Musca, Corona Australis, Serpens, IC 5146, Vela, Orion,
Monoceros R1 and R2, Rosette, Carina) derived from a star count method using an
adaptive grid and a wavelet decomposition applied to the optical data provided
by the USNO-Precision Measuring Machine. The distribution of the extinction in
the clouds leads to estimate their total individual masses M and their maximum
of extinction. I show that the relation between the mass contained within an
iso-extinction contour and the extinction is similar from cloud to cloud and
allows the extrapolation of the maximum of extinction in the range 5.7 to 25.5
magnitudes. I found that about half of the mass is contained in regions where
the visual extinction is smaller than 1 magnitude. The star count method used
on large scale (about 250 square degrees) is a powerful and relatively
straightforward method to estimate the mass of molecular complexes. A
systematic study of the all sky would lead to discover new clouds as I did in
the Lupus complex for which I found a sixth cloud of about 10^4 solar masses.
