A method, system, and data structure for the scaling down of data is
provided. At least two blocks of transformed data samples representing at
least two blocks of original data samples are received. One of at least
two tables of constants is selected wherein each table of constants is
capable of reducing the number of transformed data samples by a different
factor. The constants taken from the selected table are applied to the at
least two blocks of transformed data samples to produce one block of
transformed data samples representing one block of final data samples.
The data is processed one dimension at a time by multiplying the data in
one dimension with selected constants taken from previously developed
tables corresponding to the desired scale down factor. Scaling down by
different factors in each dimension as well as scaling down in one
dimension and scaling up in the other dimension may be achieved. In
addition, the de-quantization of the quantized transform coefficients may
be accomplished by pre-multiplication of the selected constants when the
quantization values are known. In a similar way the re-quantization may
be accomplished by a pre-division of the selected constants. Both
de-quantization and re-quantization may be combined when the input
quantized transform coefficients and output quantized transform
coefficients are desired.