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| 1 // Copyright 2015 The Chromium Authors. All rights reserved. |
| 2 // Use of this source code is governed by a BSD-style license that can be |
| 3 // found in the LICENSE file. |
| 4 |
| 5 #ifndef CC_RESOURCES_TEXTURE_COMPRESSOR_UTIL_H_ |
| 6 #define CC_RESOURCES_TEXTURE_COMPRESSOR_UTIL_H_ |
| 7 |
| 8 namespace cc { |
| 9 namespace texture_compress { |
| 10 |
| 11 #include "base/compiler_specific.h" |
| 12 #include "base/logging.h" |
| 13 |
| 14 template <typename T> |
| 15 inline T clamp(T val, T min, T max) { |
| 16 return val < min ? min : (val > max ? max : val); |
| 17 } |
| 18 |
| 19 inline uint8_t round_to_5_bits(float val) { |
| 20 return clamp<uint8_t>(val * 31.0f / 255.0f + 0.5f, 0, 31); |
| 21 } |
| 22 |
| 23 inline uint8_t round_to_4_bits(float val) { |
| 24 return clamp<uint8_t>(val * 15.0f / 255.0f + 0.5f, 0, 15); |
| 25 } |
| 26 |
| 27 union Color { |
| 28 struct BgraColorType { |
| 29 uint8_t b; |
| 30 uint8_t g; |
| 31 uint8_t r; |
| 32 uint8_t a; |
| 33 } channels; |
| 34 uint8_t components[4]; |
| 35 uint32_t bits; |
| 36 }; |
| 37 |
| 38 /* |
| 39 * Codeword tables. |
| 40 * See: Table 3.17.2 |
| 41 */ |
| 42 ALIGNAS(16) static const int16_t g_codeword_tables[8][4] = { |
| 43 {-8, -2, 2, 8}, |
| 44 {-17, -5, 5, 17}, |
| 45 {-29, -9, 9, 29}, |
| 46 {-42, -13, 13, 42}, |
| 47 {-60, -18, 18, 60}, |
| 48 {-80, -24, 24, 80}, |
| 49 {-106, -33, 33, 106}, |
| 50 {-183, -47, 47, 183}}; |
| 51 |
| 52 /* |
| 53 * Maps modifier indices to pixel index values. |
| 54 * See: Table 3.17.3 |
| 55 */ |
| 56 static const uint8_t g_mod_to_pix[4] = {3, 2, 0, 1}; |
| 57 |
| 58 /* |
| 59 * The ETC1 specification index texels as follows: |
| 60 * |
| 61 * [a][e][i][m] [ 0][ 4][ 8][12] |
| 62 * [b][f][j][n] <-> [ 1][ 5][ 9][13] |
| 63 * [c][g][k][o] [ 2][ 6][10][14] |
| 64 * [d][h][l][p] [ 3][ 7][11][15] |
| 65 * |
| 66 * [ 0][ 1][ 2][ 3] [ 0][ 4][ 4][ 5] |
| 67 * [ 4][ 5][ 6][ 7] <-> [ 8][ 9][12][13] |
| 68 * [ 8][ 9][10][11] [ 2][ 3][ 6][ 7] |
| 69 * [12][13][14][15] [10][11][14][15] |
| 70 * |
| 71 * However, when extracting sub blocks from BGRA data the natural array |
| 72 * indexing order ends up different: |
| 73 * |
| 74 * vertical0: [a][e][b][f] horizontal0: [a][e][i][m] |
| 75 * [c][g][d][h] [b][f][j][n] |
| 76 * vertical1: [i][m][j][n] horizontal1: [c][g][k][o] |
| 77 * [k][o][l][p] [d][h][l][p] |
| 78 * |
| 79 * In order to translate from the natural array indices in a sub block to the |
| 80 * indices (number) used by specification and hardware we use this table. |
| 81 */ |
| 82 static const uint8_t g_idx_to_num[4][8] = { |
| 83 {0, 4, 1, 5, 2, 6, 3, 7}, // Vertical block 0. |
| 84 {8, 12, 9, 13, 10, 14, 11, 15}, // Vertical block 1. |
| 85 {0, 4, 8, 12, 1, 5, 9, 13}, // Horizontal block 0. |
| 86 {2, 6, 10, 14, 3, 7, 11, 15} // Horizontal block 1. |
| 87 }; |
| 88 |
| 89 inline void WriteColors444(uint8_t* block, |
| 90 const Color& color0, |
| 91 const Color& color1) { |
| 92 /* for BGRA textures */ |
| 93 block[0] = (color0.channels.r & 0xf0) | (color1.channels.r >> 4); |
| 94 block[1] = (color0.channels.g & 0xf0) | (color1.channels.g >> 4); |
| 95 block[2] = (color0.channels.b & 0xf0) | (color1.channels.b >> 4); |
| 96 } |
| 97 |
| 98 inline void WriteColors555(uint8_t* block, |
| 99 const Color& color0, |
| 100 const Color& color1) { |
| 101 // Table for conversion to 3-bit two complement format. |
| 102 static const uint8_t two_compl_trans_table[8] = { |
| 103 4, // -4 (100b) |
| 104 5, // -3 (101b) |
| 105 6, // -2 (110b) |
| 106 7, // -1 (111b) |
| 107 0, // 0 (000b) |
| 108 1, // 1 (001b) |
| 109 2, // 2 (010b) |
| 110 3, // 3 (011b) |
| 111 }; |
| 112 |
| 113 int16_t delta_r = |
| 114 static_cast<int16_t>(color1.channels.r >> 3) - (color0.channels.r >> 3); |
| 115 int16_t delta_g = |
| 116 static_cast<int16_t>(color1.channels.g >> 3) - (color0.channels.g >> 3); |
| 117 int16_t delta_b = |
| 118 static_cast<int16_t>(color1.channels.b >> 3) - (color0.channels.b >> 3); |
| 119 DCHECK(delta_r >= -4 && delta_r <= 3); |
| 120 DCHECK(delta_g >= -4 && delta_g <= 3); |
| 121 DCHECK(delta_b >= -4 && delta_b <= 3); |
| 122 |
| 123 /* For BGRA textures */ |
| 124 block[0] = (color0.channels.r & 0xf8) | two_compl_trans_table[delta_r + 4]; |
| 125 block[1] = (color0.channels.g & 0xf8) | two_compl_trans_table[delta_g + 4]; |
| 126 block[2] = (color0.channels.b & 0xf8) | two_compl_trans_table[delta_b + 4]; |
| 127 } |
| 128 |
| 129 inline void WriteCodewordTable(uint8_t* block, |
| 130 uint8_t sub_block_id, |
| 131 uint8_t table) { |
| 132 DCHECK_LT(sub_block_id, 2); |
| 133 DCHECK_LT(table, 8); |
| 134 |
| 135 uint8_t shift = (2 + (3 - sub_block_id * 3)); |
| 136 block[3] &= ~(0x07 << shift); |
| 137 block[3] |= table << shift; |
| 138 } |
| 139 |
| 140 inline void WritePixelData(uint8_t* block, uint32_t pixel_data) { |
| 141 block[4] |= pixel_data >> 24; |
| 142 block[5] |= (pixel_data >> 16) & 0xff; |
| 143 block[6] |= (pixel_data >> 8) & 0xff; |
| 144 block[7] |= pixel_data & 0xff; |
| 145 } |
| 146 |
| 147 inline void WriteFlip(uint8_t* block, bool flip) { |
| 148 block[3] &= ~0x01; |
| 149 block[3] |= static_cast<uint8_t>(flip); |
| 150 } |
| 151 |
| 152 inline void WriteDiff(uint8_t* block, bool diff) { |
| 153 block[3] &= ~0x02; |
| 154 block[3] |= static_cast<uint8_t>(diff) << 1; |
| 155 } |
| 156 |
| 157 /** |
| 158 * Compress and rounds BGR888 into BGR444. The resulting BGR444 color is |
| 159 * expanded to BGR888 as it would be in hardware after decompression. The |
| 160 * actual 444-bit data is available in the four most significant bits of each |
| 161 * channel. |
| 162 */ |
| 163 inline Color MakeColor444(const float* bgr) { |
| 164 uint8_t b4 = round_to_4_bits(bgr[0]); |
| 165 uint8_t g4 = round_to_4_bits(bgr[1]); |
| 166 uint8_t r4 = round_to_4_bits(bgr[2]); |
| 167 Color bgr444; |
| 168 bgr444.channels.b = (b4 << 4) | b4; |
| 169 bgr444.channels.g = (g4 << 4) | g4; |
| 170 bgr444.channels.r = (r4 << 4) | r4; |
| 171 bgr444.channels.a = |
| 172 0x44; /* added to distinguish between expanded 555 and 444 colors */ |
| 173 return bgr444; |
| 174 } |
| 175 |
| 176 /** |
| 177 * Compress and rounds BGR888 into BGR555. The resulting BGR555 color is |
| 178 * expanded to BGR888 as it would be in hardware after decompression. The |
| 179 * actual 555-bit data is available in the five most significant bits of each |
| 180 * channel. |
| 181 */ |
| 182 inline Color MakeColor555(const float* bgr) { |
| 183 uint8_t b5 = round_to_5_bits(bgr[0]); |
| 184 uint8_t g5 = round_to_5_bits(bgr[1]); |
| 185 uint8_t r5 = round_to_5_bits(bgr[2]); |
| 186 Color bgr555; |
| 187 bgr555.channels.b = (b5 << 3) | (b5 >> 2); |
| 188 bgr555.channels.g = (g5 << 3) | (g5 >> 2); |
| 189 bgr555.channels.r = (r5 << 3) | (r5 >> 2); |
| 190 bgr555.channels.a = |
| 191 0x55; /* added to distinguish between expanded 555 and 444 colors */ |
| 192 return bgr555; |
| 193 } |
| 194 |
| 195 /** |
| 196 * Constructs a color from a given base color and luminance value. |
| 197 */ |
| 198 inline Color MakeColor(const Color& base, int16_t lum) { |
| 199 int b = static_cast<int>(base.channels.b) + lum; |
| 200 int g = static_cast<int>(base.channels.g) + lum; |
| 201 int r = static_cast<int>(base.channels.r) + lum; |
| 202 Color color; |
| 203 color.channels.b = static_cast<uint8_t>(clamp(b, 0, 255)); |
| 204 color.channels.g = static_cast<uint8_t>(clamp(g, 0, 255)); |
| 205 color.channels.r = static_cast<uint8_t>(clamp(r, 0, 255)); |
| 206 return color; |
| 207 } |
| 208 |
| 209 /** |
| 210 * Calculates the error metric for two colors. A small error signals that the |
| 211 * colors are similar to each other, a large error the signals the opposite. |
| 212 */ |
| 213 inline uint32_t GetColorError(const Color& u, const Color& v) { |
| 214 #ifdef USE_PERCEIVED_ERROR_METRIC |
| 215 float delta_b = static_cast<float>(u.channels.b) - v.channels.b; |
| 216 float delta_g = static_cast<float>(u.channels.g) - v.channels.g; |
| 217 float delta_r = static_cast<float>(u.channels.r) - v.channels.r; |
| 218 return static_cast<uint32_t>(0.299f * delta_b * delta_b + |
| 219 0.587f * delta_g * delta_g + |
| 220 0.114f * delta_r * delta_r); |
| 221 #else |
| 222 int delta_b = static_cast<int>(u.channels.b) - v.channels.b; |
| 223 int delta_g = static_cast<int>(u.channels.g) - v.channels.g; |
| 224 int delta_r = static_cast<int>(u.channels.r) - v.channels.r; |
| 225 return delta_b * delta_b + delta_g * delta_g + delta_r * delta_r; |
| 226 #endif |
| 227 } |
| 228 |
| 229 } // namespace texture_compress |
| 230 } // namespace cc |
| 231 |
| 232 #endif // CC_RESOURCES_TEXTURE_COMPRESSOR_UTIL_H_ |
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