Patent ID: 6748118
Filing Date: 2004-06-08
Classification: H04N

Abstract:
A method of quantizing signal samples of an image during image compression comprising:applying a process to transform the signal samples from a first domain to a second domain; and during the transform process, filtering signal samples, by first applying scaled filter coefficients to signal samples along the image in a first direction and then applying scaled filter coefficients to signal samples along the image in a second direction, so that at the completion of the transform process of the image, selected regions of the transformed signal samples are quantized by a common value, the selected regions are the LL, LH, HL, and HH subbands of the transformed image, and the quantization is substantially in accordance with the following form: â€ƒ&it;LL  subband  at  level  k:&it;â€ƒ&it;1Q&af;(LLk)&it;1Q&af;(LLk)=1Q&af;(LLk)â€ƒ&it;when&it;â€ƒ&it;k=K,â€ƒ&it;or&it;â€ƒ&it;1&it;â€ƒ&it;when&it;â€ƒ&it;k<K;â€ƒ&it;HL  subband  at  level  k:&it;â€ƒ&it;Q&af;(LLk)Q&af;(HLk)&it;1Q&af;(LLk)=1Q&af;(HLk);â€ƒ&it;LH  subband  at  level  k:&it;â€ƒ&it;1Q&af;(LLk)&it;Q&af;(LLk)Q&af;(LHk)=1Q&af;(LHk);HH  subband  at  level  k:&it;â€ƒ&it;Q&af;(LLk)Q&af;(HLk)&it;Q&af;(HLk)Q&af;(HHk)&it;Q&af;(LLk)=1Q&af;(HHk);K being the total level of the DWT and k being a positive integer less than or equal to K.