CGISim wraps the roman_preflight_proper diffraction model (ascl:2605.009) to simulate coronagraphic dark hole images. It generates CCD-sampled images with appropriate flux rates for specified deformable mirror settings, filters, stellar spectral types, and brightnesses, using built-in system transmission curves to estimate fluxes. Given a bandpass and spectral type, CGISim produces broadband dark hole simulations and can optionally add detector noise via an EMCCD simulator. Because it calls the underlying diffraction model directly, the software can also make use of its optional parameters, such as mask displacements.