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/* Lookup tables for fast RGB -> luminance calculation. */
static int times77[256] = {
0, 77, 154, 231, 308, 385, 462, 539,
616, 693, 770, 847, 924, 1001, 1078, 1155,
1232, 1309, 1386, 1463, 1540, 1617, 1694, 1771,
1848, 1925, 2002, 2079, 2156, 2233, 2310, 2387,
2464, 2541, 2618, 2695, 2772, 2849, 2926, 3003,
3080, 3157, 3234, 3311, 3388, 3465, 3542, 3619,
3696, 3773, 3850, 3927, 4004, 4081, 4158, 4235,
4312, 4389, 4466, 4543, 4620, 4697, 4774, 4851,
4928, 5005, 5082, 5159, 5236, 5313, 5390, 5467,
5544, 5621, 5698, 5775, 5852, 5929, 6006, 6083,
6160, 6237, 6314, 6391, 6468, 6545, 6622, 6699,
6776, 6853, 6930, 7007, 7084, 7161, 7238, 7315,
7392, 7469, 7546, 7623, 7700, 7777, 7854, 7931,
8008, 8085, 8162, 8239, 8316, 8393, 8470, 8547,
8624, 8701, 8778, 8855, 8932, 9009, 9086, 9163,
9240, 9317, 9394, 9471, 9548, 9625, 9702, 9779,
9856, 9933, 10010, 10087, 10164, 10241, 10318, 10395,
10472, 10549, 10626, 10703, 10780, 10857, 10934, 11011,
11088, 11165, 11242, 11319, 11396, 11473, 11550, 11627,
11704, 11781, 11858, 11935, 12012, 12089, 12166, 12243,
12320, 12397, 12474, 12551, 12628, 12705, 12782, 12859,
12936, 13013, 13090, 13167, 13244, 13321, 13398, 13475,
13552, 13629, 13706, 13783, 13860, 13937, 14014, 14091,
14168, 14245, 14322, 14399, 14476, 14553, 14630, 14707,
14784, 14861, 14938, 15015, 15092, 15169, 15246, 15323,
15400, 15477, 15554, 15631, 15708, 15785, 15862, 15939,
16016, 16093, 16170, 16247, 16324, 16401, 16478, 16555,
16632, 16709, 16786, 16863, 16940, 17017, 17094, 17171,
17248, 17325, 17402, 17479, 17556, 17633, 17710, 17787,
17864, 17941, 18018, 18095, 18172, 18249, 18326, 18403,
18480, 18557, 18634, 18711, 18788, 18865, 18942, 19019,
19096, 19173, 19250, 19327, 19404, 19481, 19558, 19635 };
static int times150[256] = {
0, 150, 300, 450, 600, 750, 900, 1050,
1200, 1350, 1500, 1650, 1800, 1950, 2100, 2250,
2400, 2550, 2700, 2850, 3000, 3150, 3300, 3450,
3600, 3750, 3900, 4050, 4200, 4350, 4500, 4650,
4800, 4950, 5100, 5250, 5400, 5550, 5700, 5850,
6000, 6150, 6300, 6450, 6600, 6750, 6900, 7050,
7200, 7350, 7500, 7650, 7800, 7950, 8100, 8250,
8400, 8550, 8700, 8850, 9000, 9150, 9300, 9450,
9600, 9750, 9900, 10050, 10200, 10350, 10500, 10650,
10800, 10950, 11100, 11250, 11400, 11550, 11700, 11850,
12000, 12150, 12300, 12450, 12600, 12750, 12900, 13050,
13200, 13350, 13500, 13650, 13800, 13950, 14100, 14250,
14400, 14550, 14700, 14850, 15000, 15150, 15300, 15450,
15600, 15750, 15900, 16050, 16200, 16350, 16500, 16650,
16800, 16950, 17100, 17250, 17400, 17550, 17700, 17850,
18000, 18150, 18300, 18450, 18600, 18750, 18900, 19050,
19200, 19350, 19500, 19650, 19800, 19950, 20100, 20250,
20400, 20550, 20700, 20850, 21000, 21150, 21300, 21450,
21600, 21750, 21900, 22050, 22200, 22350, 22500, 22650,
22800, 22950, 23100, 23250, 23400, 23550, 23700, 23850,
24000, 24150, 24300, 24450, 24600, 24750, 24900, 25050,
25200, 25350, 25500, 25650, 25800, 25950, 26100, 26250,
26400, 26550, 26700, 26850, 27000, 27150, 27300, 27450,
27600, 27750, 27900, 28050, 28200, 28350, 28500, 28650,
28800, 28950, 29100, 29250, 29400, 29550, 29700, 29850,
30000, 30150, 30300, 30450, 30600, 30750, 30900, 31050,
31200, 31350, 31500, 31650, 31800, 31950, 32100, 32250,
32400, 32550, 32700, 32850, 33000, 33150, 33300, 33450,
33600, 33750, 33900, 34050, 34200, 34350, 34500, 34650,
34800, 34950, 35100, 35250, 35400, 35550, 35700, 35850,
36000, 36150, 36300, 36450, 36600, 36750, 36900, 37050,
37200, 37350, 37500, 37650, 37800, 37950, 38100, 38250 };
static int times29[256] = {
0, 29, 58, 87, 116, 145, 174, 203,
232, 261, 290, 319, 348, 377, 406, 435,
464, 493, 522, 551, 580, 609, 638, 667,
696, 725, 754, 783, 812, 841, 870, 899,
928, 957, 986, 1015, 1044, 1073, 1102, 1131,
1160, 1189, 1218, 1247, 1276, 1305, 1334, 1363,
1392, 1421, 1450, 1479, 1508, 1537, 1566, 1595,
1624, 1653, 1682, 1711, 1740, 1769, 1798, 1827,
1856, 1885, 1914, 1943, 1972, 2001, 2030, 2059,
2088, 2117, 2146, 2175, 2204, 2233, 2262, 2291,
2320, 2349, 2378, 2407, 2436, 2465, 2494, 2523,
2552, 2581, 2610, 2639, 2668, 2697, 2726, 2755,
2784, 2813, 2842, 2871, 2900, 2929, 2958, 2987,
3016, 3045, 3074, 3103, 3132, 3161, 3190, 3219,
3248, 3277, 3306, 3335, 3364, 3393, 3422, 3451,
3480, 3509, 3538, 3567, 3596, 3625, 3654, 3683,
3712, 3741, 3770, 3799, 3828, 3857, 3886, 3915,
3944, 3973, 4002, 4031, 4060, 4089, 4118, 4147,
4176, 4205, 4234, 4263, 4292, 4321, 4350, 4379,
4408, 4437, 4466, 4495, 4524, 4553, 4582, 4611,
4640, 4669, 4698, 4727, 4756, 4785, 4814, 4843,
4872, 4901, 4930, 4959, 4988, 5017, 5046, 5075,
5104, 5133, 5162, 5191, 5220, 5249, 5278, 5307,
5336, 5365, 5394, 5423, 5452, 5481, 5510, 5539,
5568, 5597, 5626, 5655, 5684, 5713, 5742, 5771,
5800, 5829, 5858, 5887, 5916, 5945, 5974, 6003,
6032, 6061, 6090, 6119, 6148, 6177, 6206, 6235,
6264, 6293, 6322, 6351, 6380, 6409, 6438, 6467,
6496, 6525, 6554, 6583, 6612, 6641, 6670, 6699,
6728, 6757, 6786, 6815, 6844, 6873, 6902, 6931,
6960, 6989, 7018, 7047, 7076, 7105, 7134, 7163,
7192, 7221, 7250, 7279, 7308, 7337, 7366, 7395 };
/* The ppm_fastlumin() macro is a way to compute luminosity without
floating point arithmetic. On modern computers, floating point often isn't
any slower, so you may prefer ppm_lumin() in ppm.h.
ppm_fastlumin() works only with maxval <= 255, because the multiplication
tables go up only that high.
In the following arithmetic, note that shifting right 8 bits is the same
as dividing by (77+150+29), but some compilers may generate faster code
for >>8 than for /(77+150+29).
*/
static __inline__ pixval
ppm_fastlumin(pixel const p) {
return
(times77[PPM_GETR(p)] +
times150[PPM_GETG(p)] +
times29[PPM_GETB(p)] +
128) /* round off */
>> 8;
}
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