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src/Source/LibPNG/png.c  view on Meta::CPAN

}
#endif /* 16BIT || !FLOATING_ARITHMETIC */

/* The inverse of the above. */
png_fixed_point
png_reciprocal2(png_fixed_point a, png_fixed_point b)
{
   /* The required result is 1/a * 1/b; the following preserves accuracy. */
#ifdef PNG_FLOATING_ARITHMETIC_SUPPORTED
   double r = 1E15/a;
   r /= b;
   r = floor(r+.5);

   if (r <= 2147483647. && r >= -2147483648.)
      return (png_fixed_point)r;
#else
   /* This may overflow because the range of png_fixed_point isn't symmetric,
    * but this API is only used for the product of file and screen gamma so it
    * doesn't matter that the smallest number it can produce is 1/21474, not
    * 1/100000
    */
   png_fixed_point res = png_product2(a, b);

   if (res != 0)
      return png_reciprocal(res);
#endif

   return 0; /* overflow */
}
#endif /* READ_GAMMA */

#ifdef PNG_READ_GAMMA_SUPPORTED /* gamma table code */
#ifndef PNG_FLOATING_ARITHMETIC_SUPPORTED
/* Fixed point gamma.
 *
 * The code to calculate the tables used below can be found in the shell script
 * contrib/tools/intgamma.sh
 *
 * To calculate gamma this code implements fast log() and exp() calls using only
 * fixed point arithmetic.  This code has sufficient precision for either 8-bit
 * or 16-bit sample values.
 *
 * The tables used here were calculated using simple 'bc' programs, but C double
 * precision floating point arithmetic would work fine.
 *
 * 8-bit log table
 *   This is a table of -log(value/255)/log(2) for 'value' in the range 128 to
 *   255, so it's the base 2 logarithm of a normalized 8-bit floating point
 *   mantissa.  The numbers are 32-bit fractions.
 */
static const png_uint_32
png_8bit_l2[128] =
{
   4270715492U, 4222494797U, 4174646467U, 4127164793U, 4080044201U, 4033279239U,
   3986864580U, 3940795015U, 3895065449U, 3849670902U, 3804606499U, 3759867474U,
   3715449162U, 3671346997U, 3627556511U, 3584073329U, 3540893168U, 3498011834U,
   3455425220U, 3413129301U, 3371120137U, 3329393864U, 3287946700U, 3246774933U,
   3205874930U, 3165243125U, 3124876025U, 3084770202U, 3044922296U, 3005329011U,
   2965987113U, 2926893432U, 2888044853U, 2849438323U, 2811070844U, 2772939474U,
   2735041326U, 2697373562U, 2659933400U, 2622718104U, 2585724991U, 2548951424U,
   2512394810U, 2476052606U, 2439922311U, 2404001468U, 2368287663U, 2332778523U,
   2297471715U, 2262364947U, 2227455964U, 2192742551U, 2158222529U, 2123893754U,
   2089754119U, 2055801552U, 2022034013U, 1988449497U, 1955046031U, 1921821672U,
   1888774511U, 1855902668U, 1823204291U, 1790677560U, 1758320682U, 1726131893U,
   1694109454U, 1662251657U, 1630556815U, 1599023271U, 1567649391U, 1536433567U,
   1505374214U, 1474469770U, 1443718700U, 1413119487U, 1382670639U, 1352370686U,
   1322218179U, 1292211689U, 1262349810U, 1232631153U, 1203054352U, 1173618059U,
   1144320946U, 1115161701U, 1086139034U, 1057251672U, 1028498358U, 999877854U,
   971388940U, 943030410U, 914801076U, 886699767U, 858725327U, 830876614U,
   803152505U, 775551890U, 748073672U, 720716771U, 693480120U, 666362667U,
   639363374U, 612481215U, 585715177U, 559064263U, 532527486U, 506103872U,
   479792461U, 453592303U, 427502463U, 401522014U, 375650043U, 349885648U,
   324227938U, 298676034U, 273229066U, 247886176U, 222646516U, 197509248U,
   172473545U, 147538590U, 122703574U, 97967701U, 73330182U, 48790236U,
   24347096U, 0U

#if 0
   /* The following are the values for 16-bit tables - these work fine for the
    * 8-bit conversions but produce very slightly larger errors in the 16-bit
    * log (about 1.2 as opposed to 0.7 absolute error in the final value).  To
    * use these all the shifts below must be adjusted appropriately.
    */
   65166, 64430, 63700, 62976, 62257, 61543, 60835, 60132, 59434, 58741, 58054,
   57371, 56693, 56020, 55352, 54689, 54030, 53375, 52726, 52080, 51439, 50803,
   50170, 49542, 48918, 48298, 47682, 47070, 46462, 45858, 45257, 44661, 44068,
   43479, 42894, 42312, 41733, 41159, 40587, 40020, 39455, 38894, 38336, 37782,
   37230, 36682, 36137, 35595, 35057, 34521, 33988, 33459, 32932, 32408, 31887,
   31369, 30854, 30341, 29832, 29325, 28820, 28319, 27820, 27324, 26830, 26339,
   25850, 25364, 24880, 24399, 23920, 23444, 22970, 22499, 22029, 21562, 21098,
   20636, 20175, 19718, 19262, 18808, 18357, 17908, 17461, 17016, 16573, 16132,
   15694, 15257, 14822, 14390, 13959, 13530, 13103, 12678, 12255, 11834, 11415,
   10997, 10582, 10168, 9756, 9346, 8937, 8531, 8126, 7723, 7321, 6921, 6523,
   6127, 5732, 5339, 4947, 4557, 4169, 3782, 3397, 3014, 2632, 2251, 1872, 1495,
   1119, 744, 372
#endif
};

static png_int_32
png_log8bit(unsigned int x)
{
   unsigned int lg2 = 0;
   /* Each time 'x' is multiplied by 2, 1 must be subtracted off the final log,
    * because the log is actually negate that means adding 1.  The final
    * returned value thus has the range 0 (for 255 input) to 7.994 (for 1
    * input), return -1 for the overflow (log 0) case, - so the result is
    * always at most 19 bits.
    */
   if ((x &= 0xff) == 0)
      return -1;

   if ((x & 0xf0) == 0)
      lg2  = 4, x <<= 4;

   if ((x & 0xc0) == 0)
      lg2 += 2, x <<= 2;

   if ((x & 0x80) == 0)
      lg2 += 1, x <<= 1;

   /* result is at most 19 bits, so this cast is safe: */
   return (png_int_32)((lg2 << 16) + ((png_8bit_l2[x-128]+32768)>>16));

src/Source/LibPNG/png.c  view on Meta::CPAN

      png_ptr->options = (png_byte)((current & ~mask) | setting);

      return (current & mask) >> option;
   }

   return PNG_OPTION_INVALID;
}
#endif

/* sRGB support */
#if defined(PNG_SIMPLIFIED_READ_SUPPORTED) ||\
   defined(PNG_SIMPLIFIED_WRITE_SUPPORTED)
/* sRGB conversion tables; these are machine generated with the code in
 * contrib/tools/makesRGB.c.  The actual sRGB transfer curve defined in the
 * specification (see the article at http://en.wikipedia.org/wiki/SRGB)
 * is used, not the gamma=1/2.2 approximation use elsewhere in libpng.
 * The sRGB to linear table is exact (to the nearest 16 bit linear fraction).
 * The inverse (linear to sRGB) table has accuracies as follows:
 *
 * For all possible (255*65535+1) input values:
 *
 *    error: -0.515566 - 0.625971, 79441 (0.475369%) of readings inexact
 *
 * For the input values corresponding to the 65536 16-bit values:
 *
 *    error: -0.513727 - 0.607759, 308 (0.469978%) of readings inexact
 *
 * In all cases the inexact readings are only off by one.
 */

#ifdef PNG_SIMPLIFIED_READ_SUPPORTED
/* The convert-to-sRGB table is only currently required for read. */
const png_uint_16 png_sRGB_table[256] =
{
   0,20,40,60,80,99,119,139,
   159,179,199,219,241,264,288,313,
   340,367,396,427,458,491,526,562,
   599,637,677,718,761,805,851,898,
   947,997,1048,1101,1156,1212,1270,1330,
   1391,1453,1517,1583,1651,1720,1790,1863,
   1937,2013,2090,2170,2250,2333,2418,2504,
   2592,2681,2773,2866,2961,3058,3157,3258,
   3360,3464,3570,3678,3788,3900,4014,4129,
   4247,4366,4488,4611,4736,4864,4993,5124,
   5257,5392,5530,5669,5810,5953,6099,6246,
   6395,6547,6700,6856,7014,7174,7335,7500,
   7666,7834,8004,8177,8352,8528,8708,8889,
   9072,9258,9445,9635,9828,10022,10219,10417,
   10619,10822,11028,11235,11446,11658,11873,12090,
   12309,12530,12754,12980,13209,13440,13673,13909,
   14146,14387,14629,14874,15122,15371,15623,15878,
   16135,16394,16656,16920,17187,17456,17727,18001,
   18277,18556,18837,19121,19407,19696,19987,20281,
   20577,20876,21177,21481,21787,22096,22407,22721,
   23038,23357,23678,24002,24329,24658,24990,25325,
   25662,26001,26344,26688,27036,27386,27739,28094,
   28452,28813,29176,29542,29911,30282,30656,31033,
   31412,31794,32179,32567,32957,33350,33745,34143,
   34544,34948,35355,35764,36176,36591,37008,37429,
   37852,38278,38706,39138,39572,40009,40449,40891,
   41337,41785,42236,42690,43147,43606,44069,44534,
   45002,45473,45947,46423,46903,47385,47871,48359,
   48850,49344,49841,50341,50844,51349,51858,52369,
   52884,53401,53921,54445,54971,55500,56032,56567,
   57105,57646,58190,58737,59287,59840,60396,60955,
   61517,62082,62650,63221,63795,64372,64952,65535
};
#endif /* SIMPLIFIED_READ */

/* The base/delta tables are required for both read and write (but currently
 * only the simplified versions.)
 */
const png_uint_16 png_sRGB_base[512] =
{
   128,1782,3383,4644,5675,6564,7357,8074,
   8732,9346,9921,10463,10977,11466,11935,12384,
   12816,13233,13634,14024,14402,14769,15125,15473,
   15812,16142,16466,16781,17090,17393,17690,17981,
   18266,18546,18822,19093,19359,19621,19879,20133,
   20383,20630,20873,21113,21349,21583,21813,22041,
   22265,22487,22707,22923,23138,23350,23559,23767,
   23972,24175,24376,24575,24772,24967,25160,25352,
   25542,25730,25916,26101,26284,26465,26645,26823,
   27000,27176,27350,27523,27695,27865,28034,28201,
   28368,28533,28697,28860,29021,29182,29341,29500,
   29657,29813,29969,30123,30276,30429,30580,30730,
   30880,31028,31176,31323,31469,31614,31758,31902,
   32045,32186,32327,32468,32607,32746,32884,33021,
   33158,33294,33429,33564,33697,33831,33963,34095,
   34226,34357,34486,34616,34744,34873,35000,35127,
   35253,35379,35504,35629,35753,35876,35999,36122,
   36244,36365,36486,36606,36726,36845,36964,37083,
   37201,37318,37435,37551,37668,37783,37898,38013,
   38127,38241,38354,38467,38580,38692,38803,38915,
   39026,39136,39246,39356,39465,39574,39682,39790,
   39898,40005,40112,40219,40325,40431,40537,40642,
   40747,40851,40955,41059,41163,41266,41369,41471,
   41573,41675,41777,41878,41979,42079,42179,42279,
   42379,42478,42577,42676,42775,42873,42971,43068,
   43165,43262,43359,43456,43552,43648,43743,43839,
   43934,44028,44123,44217,44311,44405,44499,44592,
   44685,44778,44870,44962,45054,45146,45238,45329,
   45420,45511,45601,45692,45782,45872,45961,46051,
   46140,46229,46318,46406,46494,46583,46670,46758,
   46846,46933,47020,47107,47193,47280,47366,47452,
   47538,47623,47709,47794,47879,47964,48048,48133,
   48217,48301,48385,48468,48552,48635,48718,48801,
   48884,48966,49048,49131,49213,49294,49376,49458,
   49539,49620,49701,49782,49862,49943,50023,50103,
   50183,50263,50342,50422,50501,50580,50659,50738,
   50816,50895,50973,51051,51129,51207,51285,51362,
   51439,51517,51594,51671,51747,51824,51900,51977,
   52053,52129,52205,52280,52356,52432,52507,52582,
   52657,52732,52807,52881,52956,53030,53104,53178,
   53252,53326,53400,53473,53546,53620,53693,53766,
   53839,53911,53984,54056,54129,54201,54273,54345,
   54417,54489,54560,54632,54703,54774,54845,54916,
   54987,55058,55129,55199,55269,55340,55410,55480,
   55550,55620,55689,55759,55828,55898,55967,56036,
   56105,56174,56243,56311,56380,56448,56517,56585,
   56653,56721,56789,56857,56924,56992,57059,57127,
   57194,57261,57328,57395,57462,57529,57595,57662,
   57728,57795,57861,57927,57993,58059,58125,58191,
   58256,58322,58387,58453,58518,58583,58648,58713,
   58778,58843,58908,58972,59037,59101,59165,59230,
   59294,59358,59422,59486,59549,59613,59677,59740,
   59804,59867,59930,59993,60056,60119,60182,60245,
   60308,60370,60433,60495,60558,60620,60682,60744,
   60806,60868,60930,60992,61054,61115,61177,61238,
   61300,61361,61422,61483,61544,61605,61666,61727,
   61788,61848,61909,61969,62030,62090,62150,62211,
   62271,62331,62391,62450,62510,62570,62630,62689,
   62749,62808,62867,62927,62986,63045,63104,63163,
   63222,63281,63340,63398,63457,63515,63574,63632,
   63691,63749,63807,63865,63923,63981,64039,64097,
   64155,64212,64270,64328,64385,64443,64500,64557,
   64614,64672,64729,64786,64843,64900,64956,65013,
   65070,65126,65183,65239,65296,65352,65409,65465
};

const png_byte png_sRGB_delta[512] =
{
   207,201,158,129,113,100,90,82,77,72,68,64,61,59,56,54,
   52,50,49,47,46,45,43,42,41,40,39,39,38,37,36,36,
   35,34,34,33,33,32,32,31,31,30,30,30,29,29,28,28,
   28,27,27,27,27,26,26,26,25,25,25,25,24,24,24,24,
   23,23,23,23,23,22,22,22,22,22,22,21,21,21,21,21,
   21,20,20,20,20,20,20,20,20,19,19,19,19,19,19,19,
   19,18,18,18,18,18,18,18,18,18,18,17,17,17,17,17,
   17,17,17,17,17,17,16,16,16,16,16,16,16,16,16,16,
   16,16,16,16,15,15,15,15,15,15,15,15,15,15,15,15,
   15,15,15,15,14,14,14,14,14,14,14,14,14,14,14,14,
   14,14,14,14,14,14,14,13,13,13,13,13,13,13,13,13,
   13,13,13,13,13,13,13,13,13,13,13,13,13,13,12,12,
   12,12,12,12,12,12,12,12,12,12,12,12,12,12,12,12,
   12,12,12,12,12,12,12,12,12,12,12,12,11,11,11,11,