  Weak gravitational lensing induces flux dependent fluctuations in the
observed galaxy number density distribution. This cosmic magnification
(magnification bias) effect in principle enables lensing reconstruction
alternative to cosmic shear and CMB lensing. However, the intrinsic galaxy
clustering, which otherwise overwhelms the signal, has hindered its
application. Through a scaling relation found by principal component analysis
of the galaxy clustering in multi-band photometry space, we design a minimum
variance linear estimator to suppress the intrinsic galaxy clustering and to
reconstruct the lensing convergence map. In combination of the CosmoDC2 galaxy
mock and the CosmicGrowth simulation, we test this proposal for a LSST-like
galaxy survey with $ugrizY$ photometry bands. The scaling relation holds
excellently at multipole $\ell<10^3$, and remains reasonably well to $\ell\sim
3000$. The linear estimator efficiently suppresses the galaxy intrinsic
clustering, by a factor of $\sim 10^2$. For galaxies in the photo-z range
$0.8<z_\kappa<1.2$, the reconstructed convergence map is cosmic variance
limited per $\ell$ mode at $\ell<10^2$, and shot noise limited at $\ell>= 200$.
Its cross-correlation with cosmic shear of galaxies can achieve $S/N >= 200$.
When the source redshift of cosmic shear galaxies $z_\gamma<z_\kappa$, the
systematic error is negligible at all investigated scales ($\ell<3000$). When
$z_\gamma\geq z_\kappa$, the systematic error caused by the residual intrinsic
galaxy clustering becomes non-negligible. We discuss possible mitigation of the
residual intrinsic galaxy clustering required for accurate measurement at
$\ell>10^3$. This work further demonstrates the potential of lensing
measurement through cosmic magnification to enhance the weak lensing cosmology.
