  This paper provides a general introduction to the problem of image
reconstruction from interferometric data. A simple model of the interferometric
observables is given and the issues arising from sparse Fourier data are
discussed. The effects of various regularizations are described. In the
proposed general framework, most existing algorithms can be understood. For an
astronomer, such an understanding is crucial not only for selecting and using
an algorithm but also to ensure correct interpretation of the resulting image.
