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/SkColor.h"
12 #include "include/core/SkColorPriv.h"
13 #include "include/core/SkData.h"
14 #include "include/core/SkScalar.h"
15 #include "include/core/SkSize.h"
16 #include "include/private/SkColorData.h"
17 #include "include/private/base/SkTPin.h"
18 #include "include/private/base/SkTo.h"
19 #include "src/base/SkMathPriv.h"
20 #include "src/core/SkMipmap.h"
21
22 #include <algorithm>
23 #include <cstdint>
24
25 using namespace skia_private;
26
27 struct ETC1Block {
28 uint32_t fHigh;
29 uint32_t fLow;
30 };
31
32 constexpr uint32_t kFlipBit = 0x1; // set -> T/B sub-blocks; not-set -> L/R sub-blocks
33 constexpr uint32_t kDiffBit = 0x2; // set -> differential; not-set -> individual
34
extend_4To8bits(int b)35 static inline int extend_4To8bits(int b) {
36 int c = b & 0xf;
37 return (c << 4) | c;
38 }
39
extend_5To8bits(int b)40 static inline int extend_5To8bits(int b) {
41 int c = b & 0x1f;
42 return (c << 3) | (c >> 2);
43 }
44
extend_5plus3To8Bits(int base,int diff)45 static inline int extend_5plus3To8Bits(int base, int diff) {
46 static const int kLookup[8] = { 0, 1, 2, 3, -4, -3, -2, -1 };
47
48 return extend_5To8bits((0x1f & base) + kLookup[0x7 & diff]);
49 }
50
51 static const int kNumETC1ModifierTables = 8;
52 static const int kNumETC1PixelIndices = 4;
53
54 // The index of each row in this table is the ETC1 table codeword
55 // The index of each column in this table is the ETC1 pixel index value
56 static const int kETC1ModifierTables[kNumETC1ModifierTables][kNumETC1PixelIndices] = {
57 /* 0 */ { 2, 8, -2, -8 },
58 /* 1 */ { 5, 17, -5, -17 },
59 /* 2 */ { 9, 29, -9, -29 },
60 /* 3 */ { 13, 42, -13, -42 },
61 /* 4 */ { 18, 60, -18, -60 },
62 /* 5 */ { 24, 80, -24, -80 },
63 /* 6 */ { 33, 106, -33, -106 },
64 /* 7 */ { 47, 183, -47, -183 }
65 };
66
num_4x4_blocks(int size)67 static int num_4x4_blocks(int size) {
68 return ((size + 3) & ~3) >> 2;
69 }
70
71 // 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)72 static int xy_to_subblock_index(int x, int y, bool flip) {
73 SkASSERT(x >= 0 && x < 4);
74 SkASSERT(y >= 0 && y < 4);
75
76 if (flip) {
77 return y < 2 ? 0 : 1; // sub-block 1 is on top of sub-block 2
78 } else {
79 return x < 2 ? 0 : 1; // sub-block 1 is to the left of sub-block 2
80 }
81 }
82
83 struct IColor {
84 int fR, fG, fB;
85 };
86
add_delta_and_clamp(const IColor & col,int delta)87 static SkPMColor add_delta_and_clamp(const IColor& col, int delta) {
88 int r8 = SkTPin(col.fR + delta, 0, 255);
89 int g8 = SkTPin(col.fG + delta, 0, 255);
90 int b8 = SkTPin(col.fB + delta, 0, 255);
91
92 return SkPackARGB32(0xFF, r8, g8, b8);
93 }
94
decompress_etc1(SkISize dimensions,const uint8_t * srcData,SkBitmap * dst)95 static bool decompress_etc1(SkISize dimensions, const uint8_t* srcData, SkBitmap* dst) {
96 const ETC1Block* srcBlocks = reinterpret_cast<const ETC1Block*>(srcData);
97
98 int numXBlocks = num_4x4_blocks(dimensions.width());
99 int numYBlocks = num_4x4_blocks(dimensions.height());
100
101 for (int y = 0; y < numYBlocks; ++y) {
102 for (int x = 0; x < numXBlocks; ++x) {
103 const ETC1Block* curBlock1 = &srcBlocks[y * numXBlocks + x];
104 uint32_t high = SkBSwap32(curBlock1->fHigh);
105 uint32_t low = SkBSwap32(curBlock1->fLow);
106
107 bool flipped = SkToBool(high & kFlipBit);
108 bool differential = SkToBool(high & kDiffBit);
109
110 IColor colors[2];
111
112 if (differential) {
113 colors[0].fR = extend_5To8bits(high >> 27);
114 colors[1].fR = extend_5plus3To8Bits(high >> 27, high >> 24);
115 colors[0].fG = extend_5To8bits(high >> 19);
116 colors[1].fG = extend_5plus3To8Bits(high >> 19, high >> 16);
117 colors[0].fB = extend_5To8bits(high >> 11);
118 colors[1].fB = extend_5plus3To8Bits(high >> 11, high >> 8);
119 } else {
120 colors[0].fR = extend_4To8bits(high >> 28);
121 colors[1].fR = extend_4To8bits(high >> 24);
122 colors[0].fG = extend_4To8bits(high >> 20);
123 colors[1].fG = extend_4To8bits(high >> 16);
124 colors[0].fB = extend_4To8bits(high >> 12);
125 colors[1].fB = extend_4To8bits(high >> 8);
126 }
127
128 int tableIndex0 = (high >> 5) & 0x7;
129 int tableIndex1 = (high >> 2) & 0x7;
130 const int* tables[2] = {
131 kETC1ModifierTables[tableIndex0],
132 kETC1ModifierTables[tableIndex1]
133 };
134
135 int baseShift = 0;
136 int offsetX = 4 * x, offsetY = 4 * y;
137 for (int i = 0; i < 4; ++i, ++baseShift) {
138 for (int j = 0; j < 4; ++j) {
139 if (offsetX + j >= dst->width() || offsetY + i >= dst->height()) {
140 // This can happen for the topmost levels of a mipmap and for
141 // non-multiple of 4 textures
142 continue;
143 }
144
145 int subBlockIndex = xy_to_subblock_index(j, i, flipped);
146 int pixelIndex = ((low >> (baseShift+(j*4))) & 0x1) |
147 (low >> (baseShift+(j*4)+15) & 0x2);
148
149 SkASSERT(subBlockIndex == 0 || subBlockIndex == 1);
150 SkASSERT(pixelIndex >= 0 && pixelIndex < 4);
151
152 int delta = tables[subBlockIndex][pixelIndex];
153 *dst->getAddr32(offsetX + j, offsetY + i) =
154 add_delta_and_clamp(colors[subBlockIndex], delta);
155 }
156 }
157 }
158 }
159
160 return true;
161 }
162
163 //------------------------------------------------------------------------------------------------
164 struct BC1Block {
165 uint16_t fColor0;
166 uint16_t fColor1;
167 uint32_t fIndices;
168 };
169
from565(uint16_t rgb565)170 static SkPMColor from565(uint16_t rgb565) {
171 uint8_t r8 = SkR16ToR32((rgb565 >> 11) & 0x1F);
172 uint8_t g8 = SkG16ToG32((rgb565 >> 5) & 0x3F);
173 uint8_t b8 = SkB16ToB32(rgb565 & 0x1F);
174
175 return SkPackARGB32(0xFF, r8, g8, b8);
176 }
177
178 // return t*col0 + (1-t)*col1
lerp(float t,SkPMColor col0,SkPMColor col1)179 static SkPMColor lerp(float t, SkPMColor col0, SkPMColor col1) {
180 SkASSERT(SkGetPackedA32(col0) == 0xFF && SkGetPackedA32(col1) == 0xFF);
181
182 // TODO: given 't' is only either 1/3 or 2/3 this could be done faster
183 uint8_t r8 = SkScalarRoundToInt(t * SkGetPackedR32(col0) + (1.0f - t) * SkGetPackedR32(col1));
184 uint8_t g8 = SkScalarRoundToInt(t * SkGetPackedG32(col0) + (1.0f - t) * SkGetPackedG32(col1));
185 uint8_t b8 = SkScalarRoundToInt(t * SkGetPackedB32(col0) + (1.0f - t) * SkGetPackedB32(col1));
186 return SkPackARGB32(0xFF, r8, g8, b8);
187 }
188
decompress_bc1(SkISize dimensions,const uint8_t * srcData,bool isOpaque,SkBitmap * dst)189 static bool decompress_bc1(SkISize dimensions, const uint8_t* srcData,
190 bool isOpaque, SkBitmap* dst) {
191 const BC1Block* srcBlocks = reinterpret_cast<const BC1Block*>(srcData);
192
193 int numXBlocks = num_4x4_blocks(dimensions.width());
194 int numYBlocks = num_4x4_blocks(dimensions.height());
195
196 SkPMColor colors[4];
197
198 for (int y = 0; y < numYBlocks; ++y) {
199 for (int x = 0; x < numXBlocks; ++x) {
200 const BC1Block* curBlock = &srcBlocks[y * numXBlocks + x];
201
202 colors[0] = from565(curBlock->fColor0);
203 colors[1] = from565(curBlock->fColor1);
204 if (curBlock->fColor0 <= curBlock->fColor1) { // signal for a transparent block
205 colors[2] = SkPackARGB32(
206 0xFF,
207 (SkGetPackedR32(colors[0]) + SkGetPackedR32(colors[1])) >> 1,
208 (SkGetPackedG32(colors[0]) + SkGetPackedG32(colors[1])) >> 1,
209 (SkGetPackedB32(colors[0]) + SkGetPackedB32(colors[1])) >> 1);
210 // The opacity of the overall texture trumps the per-block transparency
211 colors[3] = SkPackARGB32(isOpaque ? 0xFF : 0, 0, 0, 0);
212 } else {
213 colors[2] = lerp(2.0f/3.0f, colors[0], colors[1]);
214 colors[3] = lerp(1.0f/3.0f, colors[0], colors[1]);
215 }
216
217 int shift = 0;
218 int offsetX = 4 * x, offsetY = 4 * y;
219 for (int i = 0; i < 4; ++i) {
220 for (int j = 0; j < 4; ++j, shift += 2) {
221 if (offsetX + j >= dst->width() || offsetY + i >= dst->height()) {
222 // This can happen for the topmost levels of a mipmap and for
223 // non-multiple of 4 textures
224 continue;
225 }
226
227 int index = (curBlock->fIndices >> shift) & 0x3;
228 *dst->getAddr32(offsetX + j, offsetY + i) = colors[index];
229 }
230 }
231 }
232 }
233
234 return true;
235 }
236
SkDecompress(sk_sp<SkData> data,SkISize dimensions,SkTextureCompressionType compressionType,SkBitmap * dst)237 bool SkDecompress(sk_sp<SkData> data,
238 SkISize dimensions,
239 SkTextureCompressionType compressionType,
240 SkBitmap* dst) {
241 using Type = SkTextureCompressionType;
242
243 const uint8_t* bytes = data->bytes();
244 switch (compressionType) {
245 case Type::kNone: return false;
246 case Type::kETC2_RGB8_UNORM: return decompress_etc1(dimensions, bytes, dst);
247 case Type::kBC1_RGB8_UNORM: return decompress_bc1(dimensions, bytes, true, dst);
248 case Type::kBC1_RGBA8_UNORM: return decompress_bc1(dimensions, bytes, false, dst);
249 }
250
251 SkUNREACHABLE;
252 }
253
SkCompressedDataSize(SkTextureCompressionType type,SkISize dimensions,TArray<size_t> * individualMipOffsets,bool mipmapped)254 size_t SkCompressedDataSize(SkTextureCompressionType type, SkISize dimensions,
255 TArray<size_t>* individualMipOffsets, bool mipmapped) {
256 SkASSERT(!individualMipOffsets || individualMipOffsets->empty());
257
258 int numMipLevels = 1;
259 if (mipmapped) {
260 numMipLevels = SkMipmap::ComputeLevelCount(dimensions.width(), dimensions.height()) + 1;
261 }
262
263 size_t totalSize = 0;
264 switch (type) {
265 case SkTextureCompressionType::kNone:
266 break;
267 case SkTextureCompressionType::kETC2_RGB8_UNORM:
268 case SkTextureCompressionType::kBC1_RGB8_UNORM:
269 case SkTextureCompressionType::kBC1_RGBA8_UNORM: {
270 for (int i = 0; i < numMipLevels; ++i) {
271 int numBlocks = num_4x4_blocks(dimensions.width()) *
272 num_4x4_blocks(dimensions.height());
273
274 if (individualMipOffsets) {
275 individualMipOffsets->push_back(totalSize);
276 }
277
278 static_assert(sizeof(ETC1Block) == sizeof(BC1Block));
279 totalSize += numBlocks * sizeof(ETC1Block);
280
281 dimensions = {std::max(1, dimensions.width()/2), std::max(1, dimensions.height()/2)};
282 }
283 break;
284 }
285 }
286
287 return totalSize;
288 }
289
SkCompressedBlockSize(SkTextureCompressionType type)290 size_t SkCompressedBlockSize(SkTextureCompressionType type) {
291 switch (type) {
292 case SkTextureCompressionType::kNone:
293 return 0;
294 case SkTextureCompressionType::kETC2_RGB8_UNORM:
295 return sizeof(ETC1Block);
296 case SkTextureCompressionType::kBC1_RGB8_UNORM:
297 case SkTextureCompressionType::kBC1_RGBA8_UNORM:
298 return sizeof(BC1Block);
299 }
300 SkUNREACHABLE;
301 }
302
SkCompressedFormatDataSize(SkTextureCompressionType compressionType,SkISize dimensions,bool mipmapped)303 size_t SkCompressedFormatDataSize(SkTextureCompressionType compressionType,
304 SkISize dimensions, bool mipmapped) {
305 return SkCompressedDataSize(compressionType, dimensions, nullptr, mipmapped);
306 }
307