Strictly speaking, all the physical sources are neither strictly coherent nor strictly incoherent. It is possible to exploit the coherence property of an incoherent source for complex amplitude processing. The properties that govern the coherent process are the spatial and the temporal coherence. If a desired spatial coherence must be known for a specific operation, it is possible to encode an extended source to obtain the desired spatial coherence. By simply dispersing the spectral content of an object in the Fourier domain, a desired temporal coherence can be obtained. The relationships between the source encoding and input object sampling to achieve the required spatial and temporal coherence are discussed. The use of source encoding is to relieve the basic constraint of an extended source. Signal sampling, on the other hand, is used to improve the ability of a broadband source. Since the coherence properties can be exploited from a conventional white light source, the proposed concept can be used for complex-amplitude polychromatic image processing. To confirm our discussion, examples and experimental demonstrations are provided.