Patent ID: 7558815

Claim:
A computer implemented method of reducing an error in an output of a digital image processed using a discrete cosine transform equation, the method comprising: receiving the digital image for processing using the discrete cosine transform equation; determining integer numerators and floating point denominators to approximate floating point coefficients of sub-transforms of the discrete cosine transform equation; determining truncation errors generated from performing multiplication operations using the integer numerators, wherein the multiplication operations are implemented as shift right bit operations; approximating a cumulative error in an output of the discrete cosine transform equation based on the truncation errors generated from performing the multiplication operations in the sub-transforms; modifying at least one of the sub-transforms in the discrete cosine transform equation by changing at least one of an addition operation to a subtraction operation and a subtraction operation to an addition operation performed within the at least one of the sub-transforms to reduce the cumulative error in the output of the discrete cosine transform equation; generating a modified discrete cosine transform equation including the modified at least one sub-transform; and processing the digital image using the modified discrete cosine transform equation to generate the output.