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190 lines
5.6 KiB
190 lines
5.6 KiB
/*
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* predictor.c --
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*
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* Code for predictor calculation. Its macro version, predictor.h,
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* is used in non-debugging compilation.
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*
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* Copyright (c) 1994 Kongji Huang and Brian C. Smith.
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* Cornell University
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* All rights reserved.
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*
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* Permission to use, copy, modify, and distribute this software and its
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* documentation for any purpose, without fee, and without written agreement is
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* hereby granted, provided that the above copyright notice and the following
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* two paragraphs appear in all copies of this software.
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*
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* IN NO EVENT SHALL CORNELL UNIVERSITY BE LIABLE TO ANY PARTY FOR
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* DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES ARISING OUT
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* OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN IF CORNELL
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* UNIVERSITY HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*
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* CORNELL UNIVERSITY SPECIFICALLY DISCLAIMS ANY WARRANTIES,
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* INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY
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* AND FITNESS FOR A PARTICULAR PURPOSE. THE SOFTWARE PROVIDED HEREUNDER IS
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* ON AN "AS IS" BASIS, AND CORNELL UNIVERSITY HAS NO OBLIGATION TO
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* PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
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*/
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#include <stdio.h>
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#include "mcu.h"
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#ifdef DEBUG
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/*
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*--------------------------------------------------------------
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*
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* Predict --
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*
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* Calculate the predictor for pixel[row][col][curComp],
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* i.e. curRowBuf[col][curComp]. It handles the all special
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* cases at image edges, such as first row and first column
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* of a scan.
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*
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* Results:
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* predictor is passed out.
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*
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* Side effects:
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* None.
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*
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*--------------------------------------------------------------
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*/
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void
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Predict(row,col,curComp,curRowBuf,prevRowBuf,Pr,Pt,psv,predictor)
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int row,col; /* position of the pixel to be predicted */
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int curComp; /* the pixel's component that is predicting */
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MCU *curRowBuf,*prevRowBuf; /* current and previous row of image */
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int Pr; /* data precision */
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int Pt; /* point transformation */
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int psv; /* predictor selection value */
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int *predictor; /* preditor value (output) */
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{
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int left,upper,diag,leftcol;
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leftcol=col-1;
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if (row==0) {
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/*
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* The predictor of first pixel is (1<<(Pr-Pt-1), and the
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* predictors for rest of first row are left neighbors.
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*/
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if (col==0) {
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*predictor = (1<<(Pr-Pt-1));
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}
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else {
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*predictor = curRowBuf[leftcol][curComp];
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}
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}
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else {
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/*
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* The predictors of first column are upper neighbors.
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* All other preditors are calculated according to psv.
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*/
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upper=prevRowBuf[col][curComp];
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if (col==0)
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*predictor = upper;
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else {
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left=curRowBuf[leftcol][curComp];
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diag=prevRowBuf[leftcol][curComp];
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switch (psv) {
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case 0:
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*predictor = 0;
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break;
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case 1:
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*predictor = left;
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break;
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case 2:
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*predictor = upper;
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break;
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case 3:
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*predictor = diag;
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break;
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case 4:
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*predictor = left+upper-diag;
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break;
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case 5:
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*predictor = left+((upper-diag)>>1);
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break;
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case 6:
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*predictor = upper+((left-diag)>>1);
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break;
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case 7:
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*predictor = (left+upper)>>1;
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break;
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default:
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fprintf(stderr,"Warning: Undefined PSV\n");
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*predictor = 0;
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}
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}
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}
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}
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/*
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*--------------------------------------------------------------
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*
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* QuickPredict --
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*
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* Calculate the predictor for sample curRowBuf[col][curComp].
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* It does not handle the special cases at image edges, such
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* as first row and first column of a scan. We put the special
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* case checkings outside so that the computations in main
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* loop can be simpler. This has enhenced the performance
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* significantly.
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*
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* Results:
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* predictor is passed out.
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*
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* Side effects:
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* None.
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*
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*--------------------------------------------------------------
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*/
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void
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QuickPredict(col,curComp,curRowBuf,prevRowBuf,psv,predictor)
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int col; /* column # of the pixel to be predicted */
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int curComp; /* the pixel's component that is predicting */
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MCU *curRowBuf,*prevRowBuf; /* current and previous row of image */
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int psv; /* predictor selection value */
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int *predictor; /* preditor value (output) */
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{
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int left,upper,diag,leftcol;
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leftcol=col-1;
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upper=prevRowBuf[col][curComp];
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left=curRowBuf[leftcol][curComp];
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diag=prevRowBuf[leftcol][curComp];
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/*
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* All predictor are calculated according to psv.
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*/
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switch (psv) {
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case 0:
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*predictor = 0;
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break;
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case 1:
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*predictor = left;
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break;
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case 2:
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*predictor = upper;
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break;
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case 3:
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*predictor = diag;
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break;
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case 4:
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*predictor = left+upper-diag;
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break;
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case 5:
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*predictor = left+((upper-diag)>>1);
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break;
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case 6:
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*predictor = upper+((left-diag)>>1);
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break;
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case 7:
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*predictor = (left+upper)>>1;
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break;
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default:
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fprintf(stderr,"Warning: Undefined PSV\n");
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*predictor = 0;
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}
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}
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#endif /*DEBUG*/
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