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 /*

  * Copyright 2011 Google Inc.

  *

  * Use of this source code is governed by a BSD-style license that can be

  * found in the LICENSE file.

  */

 #include "SkDither.h"

 /*  The base dither matrix we use to derive optimized ones for 565 and 4444

     { 0,  32, 8,  40, 2,  34, 10, 42 },

     { 48, 16, 56, 24, 50, 18, 58, 26 },

     { 12, 44, 4,  36, 14, 46, 6,  38 },

     { 60, 28, 52, 20, 62, 30, 54, 22 },

     { 3,  35, 11, 43, 1,  33, 9,  41 },

     { 51, 19, 59, 27, 49, 17, 57, 25 },

     { 15, 47, 7,  39, 13, 45, 5,  37 },

     { 63, 31, 55, 23, 61, 29, 53, 21 }

     The 4444 version only needs 4 bits, and given that we can reduce its size

     since the other 4x4 sub pieces all look the same once we truncate the bits.

     The 565 version only needs 3 bits for red/blue, and only 2 bits for green.

     For simplicity, we store 3 bits, and have the dither macros for green know

     this, and they shift the dither value down by 1 to make it 2 bits.

  */

 #ifdef ENABLE_DITHER_MATRIX_4X4

 const uint8_t gDitherMatrix_4Bit_4X4[4][4] = {

     {  0,  8,  2, 10 },

     { 12,  4, 14,  6 },

     {  3, 11,  1,  9 },

     { 15,  7, 13,  5 }

 };

 const uint8_t gDitherMatrix_3Bit_4X4[4][4] = {

     {  0,  4,  1,  5 },

     {  6,  2,  7,  3 },

     {  1,  5,  0,  4 },

     {  7,  3,  6,  2 }

 };

 #else   // used packed shorts for a scanlines worth of dither values

 const uint16_t gDitherMatrix_4Bit_16[4] = {

     0xA280, 0x6E4C, 0x91B3, 0x5D7F

 };

 const uint16_t gDitherMatrix_3Bit_16[4] = {

     0x5140, 0x3726, 0x4051, 0x2637

 };

 #endif