diff --git a/examples/NeoPixelBusLg/NeoPixelBusLg.ino b/examples/NeoPixelBusLg/NeoPixelBusLg.ino index 10b9b1a..c69a804 100644 --- a/examples/NeoPixelBusLg/NeoPixelBusLg.ino +++ b/examples/NeoPixelBusLg/NeoPixelBusLg.ino @@ -22,11 +22,11 @@ RgbColor white(255, 255, 255); // for your NeoPixels NeoPixelBusLg strip(PixelCount, PixelPin); -// If speed is an issue and memory is not, then you can use the gama table variant +// If speed is an issue and memory is not, then you can use the gamma table variant // which is much faster but uses 256 bytes of RAM // NeoPixelBusLg strip(PixelCount, PixelPin); -// If you want to turn gama correction off, then you can use the null gama method +// If you want to turn gamma correction off, then you can use the null gamma method // NeoPixelBusLg strip(PixelCount, PixelPin); void setup() diff --git a/src/NeoPixelBusLg.h b/src/NeoPixelBusLg.h index 29b4675..62eb9ae 100644 --- a/src/NeoPixelBusLg.h +++ b/src/NeoPixelBusLg.h @@ -74,7 +74,7 @@ public: { // does NOT affect current pixel data as there is no safe way // to reconstruct the original color values after being - // modified with both luminance and gama without storing them + // modified with both luminance and gamma without storing them _luminance = luminance; } diff --git a/src/internal/NeoGamma.cpp b/src/internal/NeoGamma.cpp index fdff9e7..0937e54 100644 --- a/src/internal/NeoGamma.cpp +++ b/src/internal/NeoGamma.cpp @@ -28,20 +28,20 @@ License along with NeoPixel. If not, see #include "NeoPixelBus.h" const uint8_t NeoGammaTableMethod::_table[] = { - 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, - 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 2, - 3, 3, 3, 3, 3, 3, 4, 4, 4, 4, 5, 5, 5, 5, 6, 6, - 6, 7, 7, 7, 7, 8, 8, 8, 9, 9, 9, 10, 10, 11, 11, 11, - 12, 12, 13, 13, 14, 14, 14, 15, 15, 16, 16, 17, 17, 18, 18, 19, - 19, 20, 20, 21, 22, 22, 23, 23, 24, 25, 25, 26, 26, 27, 28, 28, - 29, 30, 30, 31, 32, 33, 33, 34, 35, 35, 36, 37, 38, 39, 39, 40, - 41, 42, 43, 43, 44, 45, 46, 47, 48, 49, 50, 50, 51, 52, 53, 54, - 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 71, - 72, 73, 74, 75, 76, 77, 78, 80, 81, 82, 83, 84, 86, 87, 88, 89, - 91, 92, 93, 94, 96, 97, 98, 100, 101, 102, 104, 105, 106, 108, 109, 110, - 112, 113, 115, 116, 118, 119, 121, 122, 123, 125, 126, 128, 130, 131, 133, 134, - 136, 137, 139, 140, 142, 144, 145, 147, 149, 150, 152, 154, 155, 157, 159, 160, - 162, 164, 166, 167, 169, 171, 173, 175, 176, 178, 180, 182, 184, 186, 187, 189, - 191, 193, 195, 197, 199, 201, 203, 205, 207, 209, 211, 213, 215, 217, 219, 221, - 223, 225, 227, 229, 231, 233, 235, 238, 240, 242, 244, 246, 248, 251, 253, 255 + 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 16 + 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 2, // 32 + 3, 3, 3, 3, 3, 3, 4, 4, 4, 4, 5, 5, 5, 5, 6, 6, // 48 + 6, 7, 7, 7, 7, 8, 8, 8, 9, 9, 9, 10, 10, 11, 11, 11, // 64 + 12, 12, 13, 13, 14, 14, 14, 15, 15, 16, 16, 17, 17, 18, 18, 19, // 80 + 19, 20, 20, 21, 22, 22, 23, 23, 24, 25, 25, 26, 26, 27, 28, 28, // 96 + 29, 30, 30, 31, 32, 33, 33, 34, 35, 35, 36, 37, 38, 39, 39, 40, // 112 + 41, 42, 43, 43, 44, 45, 46, 47, 48, 49, 50, 50, 51, 52, 53, 54, // 128 + 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, // 144 + 71, 73, 74, 75, 76, 77, 78, 79, 81, 82, 83, 84, 85, 87, 88, 89, // 160 + 90, 91, 93, 94, 95, 97, 98, 99, 101, 102, 103, 105, 106, 107, 109, 110, // 176 + 111, 113, 114, 116, 117, 119, 120, 122, 123, 125, 126, 128, 129, 131, 132, 134, // 192 + 135, 137, 138, 140, 142, 143, 145, 146, 148, 150, 151, 153, 155, 156, 158, 160, // 208 + 162, 163, 165, 167, 168, 170, 172, 174, 176, 177, 179, 181, 183, 185, 187, 189, // 224 + 190, 192, 194, 196, 198, 200, 202, 203, 206, 207, 210, 212, 214, 216, 218, 220, // 240 + 222, 224, 226, 228, 230, 232, 234, 237, 239, 241, 243, 245, 247, 250, 251, 255 // 256 }; \ No newline at end of file diff --git a/src/internal/NeoGamma.h b/src/internal/NeoGamma.h index 2df9324..d567132 100644 --- a/src/internal/NeoGamma.h +++ b/src/internal/NeoGamma.h @@ -40,6 +40,12 @@ public: } }; +struct NeoGamma16LowHint +{ + uint8_t pos; + uint8_t count; +}; + // NeoGammaTableMethod uses 256 bytes of memory, but is significantly faster class NeoGammaTableMethod { @@ -48,16 +54,75 @@ public: { return _table[value]; } - /* + static uint16_t Correct(uint16_t value) - { -// NOTE: 16 bit color elements not supported with NeoGammaTableMethod, use NeoGammaEquationMethod - return 0; + { + // since a single monolithic table would be an unreasonable memory usage + // this will use a hybrid of two tables, the base 255 table for the hibyte + // and a smaller table with hints on how to use the table for certain values + // and the left over values some simple calculations to approximate the final + // 16 bit value as compared to the equation + static const NeoGamma16LowHint _hints[] = { + {0,16}, {1,16}, {2,16}, {3,16}, {4,16}, {5,16}, {6,16}, {7,16}, {8,16}, {9,16}, {10,16}, {11,16}, {12,16}, {13,16}, {14,16}, {15,16}, + {0,10}, {1,10}, {2,10}, {3,10}, {4,10}, {5,10}, {6,10}, {7,10}, {8,10}, {9,10}, {0,6}, {1,6}, {2,6}, {3,6}, {4,6}, {5,6}, + {0,6}, {1,6}, {2,6}, {3,6}, {4,6}, {5,6}, {0,4}, {1,4}, {2,4}, {3,4}, {0,4}, {1,4}, {2,4}, {3,4}, {0,3}, {1,3}, + {2,3}, {0,4}, {1,4}, {2,4}, {3,4}, {0,3}, {1,3}, {2,3}, {0,3}, {1,3}, {2,3}, {0,2}, {1,2}, {0,3}, {1,3}, {2,3}, + {0,2}, {1,2}, {0,2}, {1,2}, {0,3}, {1,3}, {2,3}, {0,2}, {1,2} + }; + + uint8_t hi = (value >> 8); + uint16_t lo = (value & 0x00ff); + uint8_t hiResult = _table[hi]; + uint16_t lowResult = 0; + + if (hi < countof(_hints)) + { + // use _hints table to calculate a reasonable lowbyte + lowResult = (lo + _hints[hi].pos * 256) / _hints[hi].count; + } + else if (hi == 255) + { + // last entry is always linear + lowResult = lo; + } + else + { + // check the _table for duplicate or jumps to adjust the range of lowbyte + if (hiResult == _table[hi - 1]) + { + // this result is an upper duplicate + lowResult = (lo >> 1) | 0x80; // lo / 2 + 128 + } + else + { + uint8_t delta = _table[hi + 1] - hiResult; + + if (delta == 0) + { + // this result is a lower duplicate + lowResult = (lo >> 1); // lo / 2 + } + else if (delta == 1) + { + // this result is incremental and thus linear + lowResult = lo; + } + else + { + // this result jumps by more than one, so need to spread across + lowResult = delta * lo; + } + } + + } + + return (static_cast(hiResult) << 8) + lowResult; } - */ + private: static const uint8_t _table[256]; + }; // no gamma correction at all