1 #include "SkDither.h" 2 3 /* The base dither matrix we use to derive optimized ones for 565 and 4444 4 5 { 0, 32, 8, 40, 2, 34, 10, 42 }, 6 { 48, 16, 56, 24, 50, 18, 58, 26 }, 7 { 12, 44, 4, 36, 14, 46, 6, 38 }, 8 { 60, 28, 52, 20, 62, 30, 54, 22 }, 9 { 3, 35, 11, 43, 1, 33, 9, 41 }, 10 { 51, 19, 59, 27, 49, 17, 57, 25 }, 11 { 15, 47, 7, 39, 13, 45, 5, 37 }, 12 { 63, 31, 55, 23, 61, 29, 53, 21 } 13 14 The 4444 version only needs 4 bits, and given that we can reduce its size 15 since the other 4x4 sub pieces all look the same once we truncate the bits. 16 17 The 565 version only needs 3 bits for red/blue, and only 2 bits for green. 18 For simplicity, we store 3 bits, and have the dither macros for green know 19 this, and they shift the dither value down by 1 to make it 2 bits. 20 */ 21 22 #ifdef ENABLE_DITHER_MATRIX_4X4 23 24 const uint8_t gDitherMatrix_4Bit_4X4[4][4] = { 25 { 0, 8, 2, 10 }, 26 { 12, 4, 14, 6 }, 27 { 3, 11, 1, 9 }, 28 { 15, 7, 13, 5 } 29 }; 30 31 const uint8_t gDitherMatrix_3Bit_4X4[4][4] = { 32 { 0, 4, 1, 5 }, 33 { 6, 2, 7, 3 }, 34 { 1, 5, 0, 4 }, 35 { 7, 3, 6, 2 } 36 }; 37 38 #else // used packed shorts for a scanlines worth of dither values 39 40 const uint16_t gDitherMatrix_4Bit_16[4] = { 41 0xA280, 0x6E4C, 0x91B3, 0x5D7F 42 }; 43 44 const uint16_t gDitherMatrix_3Bit_16[4] = { 45 0x5140, 0x3726, 0x4051, 0x2637 46 }; 47 48 #endif 49 50