Patent ID: 6760487
Filing Date: 2004-07-06
Classification: H04N

Abstract:
A method for reducing image blocking artifacts resulting from high JPEG image compression comprising the steps of:pre-emphasizing an original image file x with a filter P (&ohgr;,G), to form a pre-emphasis signal Xe; wherein &ohgr; is the HPF cutoff frequency corresponding to the separable DCT bandwidth Æ’ and where (&ohgr;&ap;Æ’) and G is the pre-emphasis gain; compressing the dynamic range of said pre-emphasis signal Xe into an 8-BPP range of 0-255 using a dynamic range compression (DRC) function to form a range-compressed signal Xr; using said range-compressed signal Xr to compute a MMSE optimally quantized Q-table using a Lagrange multiplier minimization function adaptQw( ); using parameters compiled in said Q-table; compressing said range-compressed signal Xr image file x using the JPEG standard IJG cjpeg( ) function to form a compressed JPEG file Xi(k); de-compressing said JPEG file Xi(k) to form a de-compressed image file x{circumflex over ( )}r; expanding said de-compressed image file using dynamic range expansion (DRE) to form an image file x{circumflex over ( )}e; de-emphasizing said image file x{circumflex over ( )}e using a filter D(&ohgr;, G) to create a x{circumflex over ( )} image; post-filtering said x{circumflex over ( )} image into an x{tilde over ( )} image, and thereafter; using an ESAP process to obtain further block smoothing of said x-image, wherein ESAP is Estimated Spectrum Adaptive Post-Filter.