Patent ID: 7643695

Claim:
An image coding apparatus for JPEG coding image data, one color component of which is expressed by the number n of bits which falls within a range from K to L bits (L>K), comprising: quantization value storage means for storing basic quantization values Qi,j; determination means for determining an allowable minimum quantization step value Qn_min specified by the number n of bits; calculation means for calculating quantization step values Q′i,j having values not less than the allowable minimum quantization step value Qn_min based on the allowable minimum quantization step value Qn_min determined by said determination means and the basic quantization values Qi,j; quantization means for quantizing transformation coefficients obtained as a result of orthogonal transformation using the calculated quantization step values Q'i,j; and Huffman encoding means for Huffman encoding the quantization coefficients obtained by said quantization means, using a Huffman table corresponding to the basic quantization values Qi,j, wherein said calculation means calculates: Q′ i,j =Max( Q n — min ,Q i,j ) (Max(a, b) is a function of selecting a larger one of a and b).