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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
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