hplx_support.c

JPEG2000实现的源码

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/* Copyright 1998, Hewlett-Packard Company                                   */
/* All rights reserved                                                       */
/* File: "hplx_support.c"                                                    */
/* Description: Extra code to get boundary extensions for lifting into       */
/*              agreement with the extensions used for convolution.          */
/* Author: Christos Chrysafis                                                */
/* Affiliation: Hewlett-Packard and                                          */
/* Version: VM8.5                                                            */
/* Last Revised: 11 September, 2000                                          */
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/* Christos Chrysafis (HPL) */
/* Flength,Slength,S L or H , L, R*/
/*****************************************************************************/
int symmetric_extension_type(int evenFilter,
                             int oddSignal,
                             int Highpass_Not_LowPass,
                             int right_Not_left)
/* The function is used for determining the type of extension
   at the boundary of a signal,
   for even or odd signal and filter length
   for the left or the right hand side of the signale,
   for the low pass or the high pass band

   returns 
     0 for whole point  extension
     1 for half  point  extension
     -1 for half  point  extension and sign flipping
     -2 for half  point  extension with the adition of a zero
                        */
{
   static int 
   ___TBL[2][2][2][2]= {{{{0, 1}, {1, 0}}, 
                         {{0, 0}, {1, 1}}},
                        {{{1, 1}, {-1,-1}}, 
                         {{1, 0}, {-1,-1}}}};

   return ___TBL[evenFilter][oddSignal][Highpass_Not_LowPass][right_Not_left];
}