Patent ID: 8582899

Claim:
An image coding apparatus comprising: a significant bit detection processing unit that detects a number of pieces of coefficient data where a significant bit is detected on a higher-order bit plane for each bit plane from coefficient data generated by performing a frequency transform on image data; a coding selection unit that selects a variable-length coding or a fixed-length coding for each bit plane on the basis of the number of pieces of coefficient data and a bit depth of the bit plane; a variable-length coding unit that performs a variable-length coding on the bit plane where the variable-length coding is selected; and a fixed-length coding unit that performs a fixed-length coding on the bit plane where the fixed-length coding is selected, wherein the variable-length coding unit performs the variable-length coding by using a coding table previously created on the basis of an occurrence probability of a coefficient bit, and the coding selection unit selects the coding in sequence from a shallower bit depth, selects the fixed-length coding for the bit plane where the bit depth is larger than or equal to a first threshold and/or the number of pieces of coefficient data on a bit plane by one higher-order is larger than or equal to a second threshold, and selects the variable-length coding for the other bit plane.