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C/C++ Source or Header  |  1992-07-08  |  3.5 KB  |  116 lines
  1. #include "mypow.h"
  2. #include "math.h"
  3.  
  4.  
  5.  
  6. long Log[256]=
  7. {0,
  8. -11348,-9928,-9098,-8508,-8051,-7678,-7362,-7089,-6848,-6632,-6437,-6258,-6094,
  9. -5943,-5801,-5669,-5545,-5428,-5317,-5212,-5112,-5017,-4926,-4839,-4755,-4675,
  10. -4598,-4523,-4451,-4382,-4315,-4250,-4187,-4126,-4066,-4008,-3952,-3898,-3845,
  11. -3793,-3742,-3693,-3645,-3597,-3551,-3506,-3462,-3419,-3377,-3336,-3295,-3255,
  12. -3216,-3178,-3140,-3104,-3067,-3032,-2997,-2962,-2928,-2895,-2862,-2830,-2798,
  13. -2767,-2736,-2706,-2676,-2647,-2618,-2589,-2561,-2533,-2505,-2478,-2451,-2425,
  14. -2399,-2373,-2348,-2323,-2298,-2273,-2249,-2225,-2201,-2178,-2155,-2132,-2109,
  15. -2087,-2065,-2043,-2021,-2000,-1978,-1957,-1937,-1916,-1896,-1876,-1856,-1836,
  16. -1816,-1797,-1778,-1759,-1740,-1721,-1702,-1684,-1666,-1648,-1630,-1612,-1595,
  17. -1577,-1560,-1543,-1526,-1509,-1492,-1476,-1459,-1443,-1427,-1411,-1395,-1379,
  18. -1363,-1348,-1332,-1317,-1302,-1286,-1271,-1256,-1242,-1227,-1212,-1198,-1184,
  19. -1169,-1155,-1141,-1127,-1113,-1099,-1086,-1072,-1059,-1045,-1032,-1019,-1005,
  20. -992,-979,-966,-954,-941,-928,-916,-903,-891,-878,-866,-854,-841,-829,-817,
  21. -805,-794,-782,-770,-758,-747,-735,-724,-712,-701,-690,-678,-667,-656,-645,
  22. -634,-623,-612,-602,-591,-580,-570,-559,-548,-538,-528,-517,-507,-497,-486,
  23. -476,-466,-456,-446,-436,-426,-416,-406,-397,-387,-377,-368,-358,-348,-339,
  24. -329,-320,-311,-301,-292,-283,-274,-264,-255,-246,-237,-228,-219,-210,-201,
  25. -193,-184,-175,-166,-158,-149,-140,-132,-123,-115,-106,-98,-89,-81,-73,-64,
  26. -56,-48,-40,-31,-23,-15,-7,0};
  27.  
  28. unsigned long mypow(int n,unsigned long x)
  29. {
  30.   long total;
  31.   long xlogn;
  32.   long newfrac,absfrac;
  33.   int count;
  34.  
  35.   if (n==0) return 0;
  36.  
  37.   
  38.   if (n==255) return (1L << (2*PowInfBase));
  39. /*
  40.   printf("n %d x %d\n",n,x);
  41. */
  42.   xlogn=x*Log[n]+(1L << (PowInfBase-1));
  43.   if (xlogn<(long) ((1L << (2*PowInfBase))*(-6.214608)) ) return(0);   /* -6.2 */
  44.   
  45.   total=(1L << (2*PowInfBase))+xlogn;
  46. /*
  47.   printf("xlogn %ld xlogn/2^PowInfBase %ld\n",xlogn,xlogn >> (PowInfBase));
  48. */  
  49.   newfrac=(xlogn >> (PowInfBase) )*(xlogn >> (PowInfBase) ) >> 1;
  50. /*
  51.   printf("total: %ld\t newfrac %ld %.5lf\n",total,newfrac,((double) total)/(1L << (2*PowInfBase)));
  52. */
  53.   count=3;
  54.   if (newfrac<0) absfrac=-newfrac; else absfrac=newfrac;
  55.   
  56.   while(absfrac> (long) (0.0001*(1L << (2*PowInfBase))) ) /* 0.0005 */
  57.     {
  58.      total+=newfrac;
  59. /*
  60.   printf("total: %ld\t newfrac %ld %.5lf\n",total,newfrac,((double) total)/(1L << (2*PowInfBase)));
  61. */
  62.       newfrac=((newfrac + (1L << (PowInfBase-1))) >> (PowInfBase)) *
  63.         ((xlogn/count)>> (PowInfBase));
  64.    if (newfrac<0) absfrac=-newfrac; else absfrac=newfrac;
  65.      count++;
  66.     }
  67.  
  68.  
  69.   total+=newfrac;
  70.  
  71. /*
  72.   printf("total: %ld\t newfrac %ld %.5lf\n",total,newfrac,((double) total)/(1L << (2*PowInfBase)));
  73. */
  74.  
  75.   return(total);
  76. }
  77.  
  78. #ifdef OLD_CODE
  79. main(int argc, char *argv[])
  80. {
  81.   int i,j,k;
  82.   double x,y,z;
  83.   
  84.   int index;            /* LUT index */
  85.   double scale;            /* scale factor (K) */
  86.   double lutVal;        /* LUT value */
  87.  
  88. /*
  89.   for(i=1;i<256;i++) 
  90.     Log[i]=(int) (log((double)i)*(1L << PowInfBase)+0.5);
  91. */
  92. /*
  93.   for(i=1;i<256;i++) 
  94.   {
  95.     Log[i]=(long) (log((double)i/255.0)*(1L <<PowInfBase)+0.5);
  96. }
  97. */
  98.   x=atof(argv[1]);
  99.   y=atof(argv[2]);
  100.  
  101.   i=mypow((int) x,((ulong) (y * (1L << PowInfBase))));
  102.   
  103.   printf("%.7lf \n",((double) i)/(1L << (PowInfBase*2)));
  104.     printf("%.7lf\n",pow(x/255.0,y));
  105.  
  106. /*
  107.       for (index = minIn; index <= maxIn; index++)
  108.     {
  109.       lutVal = minOut + scale * pow (index - minIn, gamma);
  110.       *pLut++ = (BYTE) (lutVal + 0.5);
  111.     }
  112. */
  113.  
  114. }
  115. #endif
  116.