"Fossies" - the Fresh Open Source Software Archive

Member "xzgv-0.9.2/src/dither.c" (3 Sep 2017, 2234 Bytes) of package /linux/misc/old/xzgv-0.9.2.tar.gz:

    1 /* xzgv v0.1 - picture viewer for X, with file selector.
    2  * Copyright (C) 1999 Russell Marks. See main.c for license details.
    3  *
    4  * dither.c - dithering routine.
    5  */
    6 
    7 #include <stdio.h>
    8 #include <string.h>
    9 #include <stdlib.h>
   10 #include "dither.h"
   11 
   12 
   13 static int *evenerr=NULL,*odderr=NULL;
   14 static unsigned char *dbuf=NULL;
   15 
   16 
   17 int ditherinit(int w)
   18 {
   19 ditherfinish();     /* make sure any previous mem is unallocated */
   20 if((evenerr=calloc(3*(w+10),sizeof(int)))==NULL ||
   21    (odderr =calloc(3*(w+10),sizeof(int)))==NULL ||
   22    (dbuf   =malloc(w))==NULL)
   23   return(0);
   24 else
   25   return(1);
   26 }
   27 
   28 
   29 void ditherfinish()
   30 {
   31 if(evenerr!=NULL) { free(evenerr); evenerr=NULL; }
   32 if(odderr!=NULL)  { free(odderr);  odderr=NULL; }
   33 if(dbuf!=NULL)    { free(dbuf);    dbuf=NULL; }
   34 }
   35 
   36 
   37 void ditherline(unsigned char *theline,int linenum,int width)
   38 {
   39 int x,y,lx;
   40 int c0,c1,c2,times2;
   41 int terr0,terr1,terr2,actual0,actual1,actual2;
   42 int start,addon,r,g,b;
   43 int *thiserr;
   44 int *nexterr;
   45 
   46 y=linenum;
   47 if((y&1)==0)
   48   {start=0; addon=1;
   49   thiserr=evenerr+3; nexterr=odderr+width*3;}
   50 else
   51   {start=width-1; addon=-1;
   52   thiserr=odderr+3; nexterr=evenerr+width*3;}
   53 nexterr[0]=nexterr[1]=nexterr[2]=0;
   54 x=start;
   55 for(lx=0;lx<width;lx++)
   56   {
   57   r=theline[x*3];
   58   g=theline[x*3+1];
   59   b=theline[x*3+2];
   60 
   61   terr0=r+((thiserr[0]+8)>>4);
   62   terr1=g+((thiserr[1]+8)>>4);
   63   terr2=b+((thiserr[2]+8)>>4);
   64 
   65   /* is this going to screw up on white? */  
   66   actual0=(terr0>>5)*255/7;
   67   actual1=(terr1>>5)*255/7;
   68   actual2=(terr2>>6)*255/3;
   69   
   70   if(actual0<0) actual0=0; if(actual0>255) actual0=255;
   71   if(actual1<0) actual1=0; if(actual1>255) actual1=255;
   72   if(actual2<0) actual2=0; if(actual2>255) actual2=255;
   73   
   74   c0=terr0-actual0;
   75   c1=terr1-actual1;
   76   c2=terr2-actual2;
   77 
   78   times2=(c0<<1);
   79   nexterr[-3] =c0; c0+=times2;
   80   nexterr[ 3]+=c0; c0+=times2;
   81   nexterr[ 0]+=c0; c0+=times2;
   82   thiserr[ 3]+=c0;
   83 
   84   times2=(c1<<1);
   85   nexterr[-2] =c1; c1+=times2;
   86   nexterr[ 4]+=c1; c1+=times2;
   87   nexterr[ 1]+=c1; c1+=times2;
   88   thiserr[ 4]+=c1;
   89 
   90   times2=(c2<<1);
   91   nexterr[-1] =c2; c2+=times2;
   92   nexterr[ 5]+=c2; c2+=times2;
   93   nexterr[ 2]+=c2; c2+=times2;
   94   thiserr[ 5]+=c2;
   95 
   96   dbuf[x]=(actual0>>5)*32+(actual1>>5)*4+(actual2>>6);
   97 
   98   thiserr+=3;
   99   nexterr-=3;
  100   x+=addon;
  101   }
  102 
  103 memcpy(theline,dbuf,width);
  104 }