1 /*
2 * Copyright 2020 Google Inc.
3 *
4 * Use of this source code is governed by a BSD-style license that can be
5 * found in the LICENSE file.
6 */
7
8 #include "src/core/SkCompressedDataUtils.h"
9
10 #include "include/core/SkBitmap.h"
11 #include "include/core/SkColorPriv.h"
12 #include "include/core/SkData.h"
13 #include "include/private/SkColorData.h"
14 #include "include/private/SkTPin.h"
15 #include "src/core/SkMathPriv.h"
16 #include "src/core/SkMipmap.h"
17
18 struct ETC1Block {
19 uint32_t fHigh;
20 uint32_t fLow;
21 };
22
23 constexpr uint32_t kFlipBit = 0x1; // set -> T/B sub-blocks; not-set -> L/R sub-blocks
24 constexpr uint32_t kDiffBit = 0x2; // set -> differential; not-set -> individual
25
extend_4To8bits(int b)26 static inline int extend_4To8bits(int b) {
27 int c = b & 0xf;
28 return (c << 4) | c;
29 }
30
extend_5To8bits(int b)31 static inline int extend_5To8bits(int b) {
32 int c = b & 0x1f;
33 return (c << 3) | (c >> 2);
34 }
35
extend_5plus3To8Bits(int base,int diff)36 static inline int extend_5plus3To8Bits(int base, int diff) {
37 static const int kLookup[8] = { 0, 1, 2, 3, -4, -3, -2, -1 };
38
39 return extend_5To8bits((0x1f & base) + kLookup[0x7 & diff]);
40 }
41
42 static const int kNumETC1ModifierTables = 8;
43 static const int kNumETC1PixelIndices = 4;
44
45 // The index of each row in this table is the ETC1 table codeword
46 // The index of each column in this table is the ETC1 pixel index value
47 static const int kETC1ModifierTables[kNumETC1ModifierTables][kNumETC1PixelIndices] = {
48 /* 0 */ { 2, 8, -2, -8 },
49 /* 1 */ { 5, 17, -5, -17 },
50 /* 2 */ { 9, 29, -9, -29 },
51 /* 3 */ { 13, 42, -13, -42 },
52 /* 4 */ { 18, 60, -18, -60 },
53 /* 5 */ { 24, 80, -24, -80 },
54 /* 6 */ { 33, 106, -33, -106 },
55 /* 7 */ { 47, 183, -47, -183 }
56 };
57
num_4x4_blocks(int size)58 static int num_4x4_blocks(int size) {
59 return ((size + 3) & ~3) >> 2;
60 }
61
62 // Return which sub-block a given x,y location in the overall 4x4 block belongs to
xy_to_subblock_index(int x,int y,bool flip)63 static int xy_to_subblock_index(int x, int y, bool flip) {
64 SkASSERT(x >= 0 && x < 4);
65 SkASSERT(y >= 0 && y < 4);
66
67 if (flip) {
68 return y < 2 ? 0 : 1; // sub-block 1 is on top of sub-block 2
69 } else {
70 return x < 2 ? 0 : 1; // sub-block 1 is to the left of sub-block 2
71 }
72 }
73
74 struct IColor {
75 int fR, fG, fB;
76 };
77
add_delta_and_clamp(const IColor & col,int delta)78 static SkPMColor add_delta_and_clamp(const IColor& col, int delta) {
79 int r8 = SkTPin(col.fR + delta, 0, 255);
80 int g8 = SkTPin(col.fG + delta, 0, 255);
81 int b8 = SkTPin(col.fB + delta, 0, 255);
82
83 return SkPackARGB32(0xFF, r8, g8, b8);
84 }
85
decompress_etc1(SkISize dimensions,const uint8_t * srcData,SkBitmap * dst)86 static bool decompress_etc1(SkISize dimensions, const uint8_t* srcData, SkBitmap* dst) {
87 const ETC1Block* srcBlocks = reinterpret_cast<const ETC1Block*>(srcData);
88
89 int numXBlocks = num_4x4_blocks(dimensions.width());
90 int numYBlocks = num_4x4_blocks(dimensions.height());
91
92 for (int y = 0; y < numYBlocks; ++y) {
93 for (int x = 0; x < numXBlocks; ++x) {
94 const ETC1Block* curBlock1 = &srcBlocks[y * numXBlocks + x];
95 uint32_t high = SkBSwap32(curBlock1->fHigh);
96 uint32_t low = SkBSwap32(curBlock1->fLow);
97
98 bool flipped = SkToBool(high & kFlipBit);
99 bool differential = SkToBool(high & kDiffBit);
100
101 IColor colors[2];
102
103 if (differential) {
104 colors[0].fR = extend_5To8bits(high >> 27);
105 colors[1].fR = extend_5plus3To8Bits(high >> 27, high >> 24);
106 colors[0].fG = extend_5To8bits(high >> 19);
107 colors[1].fG = extend_5plus3To8Bits(high >> 19, high >> 16);
108 colors[0].fB = extend_5To8bits(high >> 11);
109 colors[1].fB = extend_5plus3To8Bits(high >> 11, high >> 8);
110 } else {
111 colors[0].fR = extend_4To8bits(high >> 28);
112 colors[1].fR = extend_4To8bits(high >> 24);
113 colors[0].fG = extend_4To8bits(high >> 20);
114 colors[1].fG = extend_4To8bits(high >> 16);
115 colors[0].fB = extend_4To8bits(high >> 12);
116 colors[1].fB = extend_4To8bits(high >> 8);
117 }
118
119 int tableIndex0 = (high >> 5) & 0x7;
120 int tableIndex1 = (high >> 2) & 0x7;
121 const int* tables[2] = {
122 kETC1ModifierTables[tableIndex0],
123 kETC1ModifierTables[tableIndex1]
124 };
125
126 int baseShift = 0;
127 int offsetX = 4 * x, offsetY = 4 * y;
128 for (int i = 0; i < 4; ++i, ++baseShift) {
129 for (int j = 0; j < 4; ++j) {
130 if (offsetX + j >= dst->width() || offsetY + i >= dst->height()) {
131 // This can happen for the topmost levels of a mipmap and for
132 // non-multiple of 4 textures
133 continue;
134 }
135
136 int subBlockIndex = xy_to_subblock_index(j, i, flipped);
137 int pixelIndex = ((low >> (baseShift+(j*4))) & 0x1) |
138 (low >> (baseShift+(j*4)+15) & 0x2);
139
140 SkASSERT(subBlockIndex == 0 || subBlockIndex == 1);
141 SkASSERT(pixelIndex >= 0 && pixelIndex < 4);
142
143 int delta = tables[subBlockIndex][pixelIndex];
144 *dst->getAddr32(offsetX + j, offsetY + i) =
145 add_delta_and_clamp(colors[subBlockIndex], delta);
146 }
147 }
148 }
149 }
150
151 return true;
152 }
153
154 //------------------------------------------------------------------------------------------------
155 struct BC1Block {
156 uint16_t fColor0;
157 uint16_t fColor1;
158 uint32_t fIndices;
159 };
160
from565(uint16_t rgb565)161 static SkPMColor from565(uint16_t rgb565) {
162 uint8_t r8 = SkR16ToR32((rgb565 >> 11) & 0x1F);
163 uint8_t g8 = SkG16ToG32((rgb565 >> 5) & 0x3F);
164 uint8_t b8 = SkB16ToB32(rgb565 & 0x1F);
165
166 return SkPackARGB32(0xFF, r8, g8, b8);
167 }
168
169 // return t*col0 + (1-t)*col1
lerp(float t,SkPMColor col0,SkPMColor col1)170 static SkPMColor lerp(float t, SkPMColor col0, SkPMColor col1) {
171 SkASSERT(SkGetPackedA32(col0) == 0xFF && SkGetPackedA32(col1) == 0xFF);
172
173 // TODO: given 't' is only either 1/3 or 2/3 this could be done faster
174 uint8_t r8 = SkScalarRoundToInt(t * SkGetPackedR32(col0) + (1.0f - t) * SkGetPackedR32(col1));
175 uint8_t g8 = SkScalarRoundToInt(t * SkGetPackedG32(col0) + (1.0f - t) * SkGetPackedG32(col1));
176 uint8_t b8 = SkScalarRoundToInt(t * SkGetPackedB32(col0) + (1.0f - t) * SkGetPackedB32(col1));
177 return SkPackARGB32(0xFF, r8, g8, b8);
178 }
179
decompress_bc1(SkISize dimensions,const uint8_t * srcData,bool isOpaque,SkBitmap * dst)180 static bool decompress_bc1(SkISize dimensions, const uint8_t* srcData,
181 bool isOpaque, SkBitmap* dst) {
182 const BC1Block* srcBlocks = reinterpret_cast<const BC1Block*>(srcData);
183
184 int numXBlocks = num_4x4_blocks(dimensions.width());
185 int numYBlocks = num_4x4_blocks(dimensions.height());
186
187 SkPMColor colors[4];
188
189 for (int y = 0; y < numYBlocks; ++y) {
190 for (int x = 0; x < numXBlocks; ++x) {
191 const BC1Block* curBlock = &srcBlocks[y * numXBlocks + x];
192
193 colors[0] = from565(curBlock->fColor0);
194 colors[1] = from565(curBlock->fColor1);
195 if (curBlock->fColor0 <= curBlock->fColor1) { // signal for a transparent block
196 colors[2] = SkPackARGB32(
197 0xFF,
198 (SkGetPackedR32(colors[0]) + SkGetPackedR32(colors[1])) >> 1,
199 (SkGetPackedG32(colors[0]) + SkGetPackedG32(colors[1])) >> 1,
200 (SkGetPackedB32(colors[0]) + SkGetPackedB32(colors[1])) >> 1);
201 // The opacity of the overall texture trumps the per-block transparency
202 colors[3] = SkPackARGB32(isOpaque ? 0xFF : 0, 0, 0, 0);
203 } else {
204 colors[2] = lerp(2.0f/3.0f, colors[0], colors[1]);
205 colors[3] = lerp(1.0f/3.0f, colors[0], colors[1]);
206 }
207
208 int shift = 0;
209 int offsetX = 4 * x, offsetY = 4 * y;
210 for (int i = 0; i < 4; ++i) {
211 for (int j = 0; j < 4; ++j, shift += 2) {
212 if (offsetX + j >= dst->width() || offsetY + i >= dst->height()) {
213 // This can happen for the topmost levels of a mipmap and for
214 // non-multiple of 4 textures
215 continue;
216 }
217
218 int index = (curBlock->fIndices >> shift) & 0x3;
219 *dst->getAddr32(offsetX + j, offsetY + i) = colors[index];
220 }
221 }
222 }
223 }
224
225 return true;
226 }
227
SkDecompress(sk_sp<SkData> data,SkISize dimensions,SkImage::CompressionType compressionType,SkBitmap * dst)228 bool SkDecompress(sk_sp<SkData> data,
229 SkISize dimensions,
230 SkImage::CompressionType compressionType,
231 SkBitmap* dst) {
232 using Type = SkImage::CompressionType;
233
234 const uint8_t* bytes = data->bytes();
235 switch (compressionType) {
236 case Type::kNone: return false;
237 case Type::kETC2_RGB8_UNORM: return decompress_etc1(dimensions, bytes, dst);
238 case Type::kBC1_RGB8_UNORM: return decompress_bc1(dimensions, bytes, true, dst);
239 case Type::kBC1_RGBA8_UNORM: return decompress_bc1(dimensions, bytes, false, dst);
240 }
241
242 SkUNREACHABLE;
243 return false;
244 }
245
SkCompressedDataSize(SkImage::CompressionType type,SkISize dimensions,SkTArray<size_t> * individualMipOffsets,bool mipMapped)246 size_t SkCompressedDataSize(SkImage::CompressionType type, SkISize dimensions,
247 SkTArray<size_t>* individualMipOffsets, bool mipMapped) {
248 SkASSERT(!individualMipOffsets || !individualMipOffsets->count());
249
250 int numMipLevels = 1;
251 if (mipMapped) {
252 numMipLevels = SkMipmap::ComputeLevelCount(dimensions.width(), dimensions.height()) + 1;
253 }
254
255 size_t totalSize = 0;
256 switch (type) {
257 case SkImage::CompressionType::kNone:
258 break;
259 case SkImage::CompressionType::kETC2_RGB8_UNORM:
260 case SkImage::CompressionType::kBC1_RGB8_UNORM:
261 case SkImage::CompressionType::kBC1_RGBA8_UNORM: {
262 for (int i = 0; i < numMipLevels; ++i) {
263 int numBlocks = num_4x4_blocks(dimensions.width()) *
264 num_4x4_blocks(dimensions.height());
265
266 if (individualMipOffsets) {
267 individualMipOffsets->push_back(totalSize);
268 }
269
270 static_assert(sizeof(ETC1Block) == sizeof(BC1Block));
271 totalSize += numBlocks * sizeof(ETC1Block);
272
273 dimensions = {std::max(1, dimensions.width()/2), std::max(1, dimensions.height()/2)};
274 }
275 break;
276 }
277 }
278
279 return totalSize;
280 }
281
SkCompressedBlockSize(SkImage::CompressionType type)282 size_t SkCompressedBlockSize(SkImage::CompressionType type) {
283 switch (type) {
284 case SkImage::CompressionType::kNone:
285 return 0;
286 case SkImage::CompressionType::kETC2_RGB8_UNORM:
287 return sizeof(ETC1Block);
288 case SkImage::CompressionType::kBC1_RGB8_UNORM:
289 case SkImage::CompressionType::kBC1_RGBA8_UNORM:
290 return sizeof(BC1Block);
291 }
292 SkUNREACHABLE;
293 }
294
SkCompressedFormatDataSize(SkImage::CompressionType compressionType,SkISize dimensions,bool mipMapped)295 size_t SkCompressedFormatDataSize(SkImage::CompressionType compressionType,
296 SkISize dimensions, bool mipMapped) {
297 return SkCompressedDataSize(compressionType, dimensions, nullptr, mipMapped);
298 }
299