Patent ID: 6873739

Claim:
An image compression apparatus comprising: a wavelet transformer which receives digital image data, wavelet-transforms the digital image data in at least one step, and divides the digital image data into a first wavelet region having the lowest frequency and a second wavelet region having the other frequency, to thereby output image data of the first wavelet region and image data of the second wavelet region; a quantizer which receives both the image data of the first and second wavelet regions and respectively quantizes the image data of the first and second wavelet regions to thereby output first quantization data formed of first quantization coefficients and second quantization data formed of second quantization coefficients, respectively; a comparator which receives the first quantization data and compares the first quantization coefficients of the first quantization data, to thereby output the maximum quantization coefficient having the maximum quantization coefficient value and the minimum quantization coefficient having the minimum quantization coefficient value, among the first quantization coefficients; a subtracter which receives the maximum quantization coefficient and the minimum quantization coefficient output from the comparator and subtracts the latter from the former, to thereby output a subtraction constant; a low data compressor which receives the first quantization data and the subtraction constant and subtracts the subtraction constant from the first quantization coefficients of the first quantization data, to thereby output low compression data obtained by compressing the first quantization data; and a high data compressor which sequentially receives the second quantization coefficients of the second quantization data and sequentially generates first compression data obtained by coding the number of zero quantization coefficients each having at least one successive zero value among the second quantization coefficients, and second compression data obtained by coding the second quantization coefficients other than the zero quantization coefficients according to a coding rule with reference to the coding rule where compression codes are established according to a respective quantization coefficient, to thereby output high compression data.