During a solar eclipse, the solar illuminance varies with time depending on the phase of the eclipse. Measuring the solar illuminance during a solar eclipse has been one of the most common projects conducted by students as well as amateur astronomers owing to the simplicity of its measurement. Despite extensive measurements conducted during previous eclipse events, only a few studies have presented methods for modeling the solar illuminance variations. In this study, we have proposed and compared several methods for modeling the variation in the normalized solar illuminance during solar eclipses by using the solar image data taken by spacecraft. We show that the solar continuum image data obtained by the Solar and Heliospheric Observatory (SOHO) and the Solar Dynamics Observatory (SDO) spacecraft can be used for developing an ideal model for solar illuminance variation during a total and annular solar eclipse.