In discrete-cosine-transform-based (DCT-based) compressions
such as JPEG it is a common practice to use the same quantization
matrix for both encoding and decoding. However, this need not be
the case, and the flexibility of designing different matrices for
encoding and decoding allows us to perform image restoration in the DCT
domain. This is especially useful when we have severe limitations
on the computational power, for instance, with in-camera image
manipulation for programmable digital cameras. We provide an
algorithm that compensates partially for a defocus error in image
acquisition, and experimental results show that the restored image is
closer to the in-focus image than is the defocused image.
© 1998 Optical Society of America
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