  We present a model of cosmic ray injection into the Galactic space based on
recent gamma-ray observations of supernova remnants (SNRs) and pulsar wind
nebulae (PWNe) by the Fermi Large Area Telescope and imaging atmospheric
Cherenkov telescopes. Steady-state (SS) injection of nuclear particles and
electrons (e^-) from the Galactic ensemble of SNRs, and electrons and positrons
(e^+) from the Galactic ensemble of PWNe are assumed, with their injection
spectra inferred under guidance of gamma-ray observations and recent
development of evolution and emission models. The ensembles of SNRs and PWNe
are assumed to share the same spatial distributions. Assessment of possible
secondary CR contribution from dense molecular clouds interacting with SNRs is
also given. CR propagation in the interstellar space is handled by GALPROP.
Different underlying source distribution models and Galaxy halo sizes are
employed to estimate the systematic uncertainty of the model. We show that this
observation-based model reproduces the positron fraction e^+/(e^- + e^+) and
antiproton-to-proton ratio reported by Pamela and other previous missions
reasonably well, without calling for any speculative sources. A discrepancy
remains, however, between the total e^- + e^+ spectrum measured by Fermi and
our model below 20GeV, for which the potential causes are discussed. Important
quantities for Galactic CRs including their energy injection, average lifetime,
and mean gas density along their typical propagation path are also estimated.
