1 2 /* 3 * Copyright 2012 Google Inc. 4 * 5 * Use of this source code is governed by a BSD-style license that can be 6 * found in the LICENSE file. 7 */ 8 9 #include "SkSweepGradient.h" 10 11 SkSweepGradient::SkSweepGradient(SkScalar cx, SkScalar cy, const SkColor colors[], 12 const SkScalar pos[], int count, SkUnitMapper* mapper) 13 : SkGradientShaderBase(colors, pos, count, SkShader::kClamp_TileMode, mapper), 14 fCenter(SkPoint::Make(cx, cy)) 15 { 16 fPtsToUnit.setTranslate(-cx, -cy); 17 } 18 19 SkShader::BitmapType SkSweepGradient::asABitmap(SkBitmap* bitmap, 20 SkMatrix* matrix, SkShader::TileMode* xy) const { 21 if (bitmap) { 22 this->getGradientTableBitmap(bitmap); 23 } 24 if (matrix) { 25 *matrix = fPtsToUnit; 26 } 27 if (xy) { 28 xy[0] = fTileMode; 29 xy[1] = kClamp_TileMode; 30 } 31 return kSweep_BitmapType; 32 } 33 34 SkShader::GradientType SkSweepGradient::asAGradient(GradientInfo* info) const { 35 if (info) { 36 commonAsAGradient(info); 37 info->fPoint[0] = fCenter; 38 } 39 return kSweep_GradientType; 40 } 41 42 SkSweepGradient::SkSweepGradient(SkFlattenableReadBuffer& buffer) 43 : INHERITED(buffer), 44 fCenter(buffer.readPoint()) { 45 } 46 47 void SkSweepGradient::flatten(SkFlattenableWriteBuffer& buffer) const { 48 this->INHERITED::flatten(buffer); 49 buffer.writePoint(fCenter); 50 } 51 52 #ifndef SK_SCALAR_IS_FLOAT 53 #ifdef COMPUTE_SWEEP_TABLE 54 #define PI 3.14159265 55 static bool gSweepTableReady; 56 static uint8_t gSweepTable[65]; 57 58 /* Our table stores precomputed values for atan: [0...1] -> [0..PI/4] 59 We scale the results to [0..32] 60 */ 61 static const uint8_t* build_sweep_table() { 62 if (!gSweepTableReady) { 63 const int N = 65; 64 const double DENOM = N - 1; 65 66 for (int i = 0; i < N; i++) 67 { 68 double arg = i / DENOM; 69 double v = atan(arg); 70 int iv = (int)round(v * DENOM * 2 / PI); 71 // printf("[%d] atan(%g) = %g %d\n", i, arg, v, iv); 72 printf("%d, ", iv); 73 gSweepTable[i] = iv; 74 } 75 gSweepTableReady = true; 76 } 77 return gSweepTable; 78 } 79 #else 80 static const uint8_t gSweepTable[] = { 81 0, 1, 1, 2, 3, 3, 4, 4, 5, 6, 6, 7, 8, 8, 9, 9, 82 10, 11, 11, 12, 12, 13, 13, 14, 15, 15, 16, 16, 17, 17, 18, 18, 83 19, 19, 20, 20, 21, 21, 22, 22, 23, 23, 24, 24, 25, 25, 25, 26, 84 26, 27, 27, 27, 28, 28, 29, 29, 29, 30, 30, 30, 31, 31, 31, 32, 85 32 86 }; 87 static const uint8_t* build_sweep_table() { return gSweepTable; } 88 #endif 89 #endif 90 91 // divide numer/denom, with a bias of 6bits. Assumes numer <= denom 92 // and denom != 0. Since our table is 6bits big (+1), this is a nice fit. 93 // Same as (but faster than) SkFixedDiv(numer, denom) >> 10 94 95 //unsigned div_64(int numer, int denom); 96 #ifndef SK_SCALAR_IS_FLOAT 97 static unsigned div_64(int numer, int denom) { 98 SkASSERT(numer <= denom); 99 SkASSERT(numer > 0); 100 SkASSERT(denom > 0); 101 102 int nbits = SkCLZ(numer); 103 int dbits = SkCLZ(denom); 104 int bits = 6 - nbits + dbits; 105 SkASSERT(bits <= 6); 106 107 if (bits < 0) { // detect underflow 108 return 0; 109 } 110 111 denom <<= dbits - 1; 112 numer <<= nbits - 1; 113 114 unsigned result = 0; 115 116 // do the first one 117 if ((numer -= denom) >= 0) { 118 result = 1; 119 } else { 120 numer += denom; 121 } 122 123 // Now fall into our switch statement if there are more bits to compute 124 if (bits > 0) { 125 // make room for the rest of the answer bits 126 result <<= bits; 127 switch (bits) { 128 case 6: 129 if ((numer = (numer << 1) - denom) >= 0) 130 result |= 32; 131 else 132 numer += denom; 133 case 5: 134 if ((numer = (numer << 1) - denom) >= 0) 135 result |= 16; 136 else 137 numer += denom; 138 case 4: 139 if ((numer = (numer << 1) - denom) >= 0) 140 result |= 8; 141 else 142 numer += denom; 143 case 3: 144 if ((numer = (numer << 1) - denom) >= 0) 145 result |= 4; 146 else 147 numer += denom; 148 case 2: 149 if ((numer = (numer << 1) - denom) >= 0) 150 result |= 2; 151 else 152 numer += denom; 153 case 1: 154 default: // not strictly need, but makes GCC make better ARM code 155 if ((numer = (numer << 1) - denom) >= 0) 156 result |= 1; 157 else 158 numer += denom; 159 } 160 } 161 return result; 162 } 163 #endif 164 165 // Given x,y in the first quadrant, return 0..63 for the angle [0..90] 166 #ifndef SK_SCALAR_IS_FLOAT 167 static unsigned atan_0_90(SkFixed y, SkFixed x) { 168 #ifdef SK_DEBUG 169 { 170 static bool gOnce; 171 if (!gOnce) { 172 gOnce = true; 173 SkASSERT(div_64(55, 55) == 64); 174 SkASSERT(div_64(128, 256) == 32); 175 SkASSERT(div_64(2326528, 4685824) == 31); 176 SkASSERT(div_64(753664, 5210112) == 9); 177 SkASSERT(div_64(229376, 4882432) == 3); 178 SkASSERT(div_64(2, 64) == 2); 179 SkASSERT(div_64(1, 64) == 1); 180 // test that we handle underflow correctly 181 SkASSERT(div_64(12345, 0x54321234) == 0); 182 } 183 } 184 #endif 185 186 SkASSERT(y > 0 && x > 0); 187 const uint8_t* table = build_sweep_table(); 188 189 unsigned result; 190 bool swap = (x < y); 191 if (swap) { 192 // first part of the atan(v) = PI/2 - atan(1/v) identity 193 // since our div_64 and table want v <= 1, where v = y/x 194 SkTSwap<SkFixed>(x, y); 195 } 196 197 result = div_64(y, x); 198 199 #ifdef SK_DEBUG 200 { 201 unsigned result2 = SkDivBits(y, x, 6); 202 SkASSERT(result2 == result || 203 (result == 1 && result2 == 0)); 204 } 205 #endif 206 207 SkASSERT(result < SK_ARRAY_COUNT(gSweepTable)); 208 result = table[result]; 209 210 if (swap) { 211 // complete the atan(v) = PI/2 - atan(1/v) identity 212 result = 64 - result; 213 // pin to 63 214 result -= result >> 6; 215 } 216 217 SkASSERT(result <= 63); 218 return result; 219 } 220 #endif 221 222 // returns angle in a circle [0..2PI) -> [0..255] 223 #ifdef SK_SCALAR_IS_FLOAT 224 static unsigned SkATan2_255(float y, float x) { 225 // static const float g255Over2PI = 255 / (2 * SK_ScalarPI); 226 static const float g255Over2PI = 40.584510488433314f; 227 228 float result = sk_float_atan2(y, x); 229 if (result < 0) { 230 result += 2 * SK_ScalarPI; 231 } 232 SkASSERT(result >= 0); 233 // since our value is always >= 0, we can cast to int, which is faster than 234 // calling floorf() 235 int ir = (int)(result * g255Over2PI); 236 SkASSERT(ir >= 0 && ir <= 255); 237 return ir; 238 } 239 #else 240 static unsigned SkATan2_255(SkFixed y, SkFixed x) { 241 if (x == 0) { 242 if (y == 0) { 243 return 0; 244 } 245 return y < 0 ? 192 : 64; 246 } 247 if (y == 0) { 248 return x < 0 ? 128 : 0; 249 } 250 251 /* Find the right quadrant for x,y 252 Since atan_0_90 only handles the first quadrant, we rotate x,y 253 appropriately before calling it, and then add the right amount 254 to account for the real quadrant. 255 quadrant 0 : add 0 | x > 0 && y > 0 256 quadrant 1 : add 64 (90 degrees) | x < 0 && y > 0 257 quadrant 2 : add 128 (180 degrees) | x < 0 && y < 0 258 quadrant 3 : add 192 (270 degrees) | x > 0 && y < 0 259 260 map x<0 to (1 << 6) 261 map y<0 to (3 << 6) 262 add = map_x ^ map_y 263 */ 264 int xsign = x >> 31; 265 int ysign = y >> 31; 266 int add = ((-xsign) ^ (ysign & 3)) << 6; 267 268 #ifdef SK_DEBUG 269 if (0 == add) 270 SkASSERT(x > 0 && y > 0); 271 else if (64 == add) 272 SkASSERT(x < 0 && y > 0); 273 else if (128 == add) 274 SkASSERT(x < 0 && y < 0); 275 else if (192 == add) 276 SkASSERT(x > 0 && y < 0); 277 else 278 SkDEBUGFAIL("bad value for add"); 279 #endif 280 281 /* This ^ trick makes x, y positive, and the swap<> handles quadrants 282 where we need to rotate x,y by 90 or -90 283 */ 284 x = (x ^ xsign) - xsign; 285 y = (y ^ ysign) - ysign; 286 if (add & 64) { // quads 1 or 3 need to swap x,y 287 SkTSwap<SkFixed>(x, y); 288 } 289 290 unsigned result = add + atan_0_90(y, x); 291 SkASSERT(result < 256); 292 return result; 293 } 294 #endif 295 296 void SkSweepGradient::shadeSpan(int x, int y, SkPMColor* SK_RESTRICT dstC, 297 int count) { 298 SkMatrix::MapXYProc proc = fDstToIndexProc; 299 const SkMatrix& matrix = fDstToIndex; 300 const SkPMColor* SK_RESTRICT cache = this->getCache32(); 301 SkPoint srcPt; 302 303 if (fDstToIndexClass != kPerspective_MatrixClass) { 304 proc(matrix, SkIntToScalar(x) + SK_ScalarHalf, 305 SkIntToScalar(y) + SK_ScalarHalf, &srcPt); 306 SkScalar dx, fx = srcPt.fX; 307 SkScalar dy, fy = srcPt.fY; 308 309 if (fDstToIndexClass == kFixedStepInX_MatrixClass) { 310 SkFixed storage[2]; 311 (void)matrix.fixedStepInX(SkIntToScalar(y) + SK_ScalarHalf, 312 &storage[0], &storage[1]); 313 dx = SkFixedToScalar(storage[0]); 314 dy = SkFixedToScalar(storage[1]); 315 } else { 316 SkASSERT(fDstToIndexClass == kLinear_MatrixClass); 317 dx = matrix.getScaleX(); 318 dy = matrix.getSkewY(); 319 } 320 321 for (; count > 0; --count) { 322 *dstC++ = cache[SkATan2_255(fy, fx)]; 323 fx += dx; 324 fy += dy; 325 } 326 } else { // perspective case 327 for (int stop = x + count; x < stop; x++) { 328 proc(matrix, SkIntToScalar(x) + SK_ScalarHalf, 329 SkIntToScalar(y) + SK_ScalarHalf, &srcPt); 330 *dstC++ = cache[SkATan2_255(srcPt.fY, srcPt.fX)]; 331 } 332 } 333 } 334 335 void SkSweepGradient::shadeSpan16(int x, int y, uint16_t* SK_RESTRICT dstC, 336 int count) { 337 SkMatrix::MapXYProc proc = fDstToIndexProc; 338 const SkMatrix& matrix = fDstToIndex; 339 const uint16_t* SK_RESTRICT cache = this->getCache16(); 340 int toggle = init_dither_toggle16(x, y); 341 SkPoint srcPt; 342 343 if (fDstToIndexClass != kPerspective_MatrixClass) { 344 proc(matrix, SkIntToScalar(x) + SK_ScalarHalf, 345 SkIntToScalar(y) + SK_ScalarHalf, &srcPt); 346 SkScalar dx, fx = srcPt.fX; 347 SkScalar dy, fy = srcPt.fY; 348 349 if (fDstToIndexClass == kFixedStepInX_MatrixClass) { 350 SkFixed storage[2]; 351 (void)matrix.fixedStepInX(SkIntToScalar(y) + SK_ScalarHalf, 352 &storage[0], &storage[1]); 353 dx = SkFixedToScalar(storage[0]); 354 dy = SkFixedToScalar(storage[1]); 355 } else { 356 SkASSERT(fDstToIndexClass == kLinear_MatrixClass); 357 dx = matrix.getScaleX(); 358 dy = matrix.getSkewY(); 359 } 360 361 for (; count > 0; --count) { 362 int index = SkATan2_255(fy, fx) >> (8 - kCache16Bits); 363 *dstC++ = cache[toggle + index]; 364 toggle = next_dither_toggle16(toggle); 365 fx += dx; 366 fy += dy; 367 } 368 } else { // perspective case 369 for (int stop = x + count; x < stop; x++) { 370 proc(matrix, SkIntToScalar(x) + SK_ScalarHalf, 371 SkIntToScalar(y) + SK_ScalarHalf, &srcPt); 372 373 int index = SkATan2_255(srcPt.fY, srcPt.fX); 374 index >>= (8 - kCache16Bits); 375 *dstC++ = cache[toggle + index]; 376 toggle = next_dither_toggle16(toggle); 377 } 378 } 379 } 380 381 ///////////////////////////////////////////////////////////////////// 382 383 #if SK_SUPPORT_GPU 384 385 #include "GrTBackendEffectFactory.h" 386 387 class GrGLSweepGradient : public GrGLGradientEffect { 388 public: 389 390 GrGLSweepGradient(const GrBackendEffectFactory& factory, 391 const GrEffectRef&) : INHERITED (factory) { } 392 virtual ~GrGLSweepGradient() { } 393 394 virtual void emitCode(GrGLShaderBuilder*, 395 const GrEffectStage&, 396 EffectKey, 397 const char* vertexCoords, 398 const char* outputColor, 399 const char* inputColor, 400 const TextureSamplerArray&) SK_OVERRIDE; 401 402 static EffectKey GenKey(const GrEffectStage& stage, const GrGLCaps&) { 403 return GenMatrixKey(stage); 404 } 405 406 private: 407 408 typedef GrGLGradientEffect INHERITED; 409 410 }; 411 412 ///////////////////////////////////////////////////////////////////// 413 414 class GrSweepGradient : public GrGradientEffect { 415 public: 416 static GrEffectRef* Create(GrContext* ctx, 417 const SkSweepGradient& shader, 418 const SkMatrix& matrix) { 419 AutoEffectUnref effect(SkNEW_ARGS(GrSweepGradient, (ctx, shader, matrix))); 420 return CreateEffectRef(effect); 421 } 422 virtual ~GrSweepGradient() { } 423 424 static const char* Name() { return "Sweep Gradient"; } 425 virtual const GrBackendEffectFactory& getFactory() const SK_OVERRIDE { 426 return GrTBackendEffectFactory<GrSweepGradient>::getInstance(); 427 } 428 429 typedef GrGLSweepGradient GLEffect; 430 431 private: 432 GrSweepGradient(GrContext* ctx, 433 const SkSweepGradient& shader, 434 const SkMatrix& matrix) 435 : INHERITED(ctx, shader, matrix, SkShader::kClamp_TileMode) { } 436 GR_DECLARE_EFFECT_TEST; 437 438 typedef GrGradientEffect INHERITED; 439 }; 440 441 ///////////////////////////////////////////////////////////////////// 442 443 GR_DEFINE_EFFECT_TEST(GrSweepGradient); 444 445 GrEffectRef* GrSweepGradient::TestCreate(SkRandom* random, 446 GrContext* context, 447 GrTexture**) { 448 SkPoint center = {random->nextUScalar1(), random->nextUScalar1()}; 449 450 SkColor colors[kMaxRandomGradientColors]; 451 SkScalar stopsArray[kMaxRandomGradientColors]; 452 SkScalar* stops = stopsArray; 453 SkShader::TileMode tmIgnored; 454 int colorCount = RandomGradientParams(random, colors, &stops, &tmIgnored); 455 SkAutoTUnref<SkShader> shader(SkGradientShader::CreateSweep(center.fX, center.fY, 456 colors, stops, colorCount)); 457 SkPaint paint; 458 return shader->asNewEffect(context, paint); 459 } 460 461 ///////////////////////////////////////////////////////////////////// 462 463 void GrGLSweepGradient::emitCode(GrGLShaderBuilder* builder, 464 const GrEffectStage& stage, 465 EffectKey key, 466 const char* vertexCoords, 467 const char* outputColor, 468 const char* inputColor, 469 const TextureSamplerArray& samplers) { 470 this->emitYCoordUniform(builder); 471 const char* coords; 472 this->setupMatrix(builder, key, vertexCoords, &coords); 473 SkString t; 474 t.printf("atan(- %s.y, - %s.x) * 0.1591549430918 + 0.5", coords, coords); 475 this->emitColorLookup(builder, t.c_str(), outputColor, inputColor, samplers[0]); 476 } 477 478 ///////////////////////////////////////////////////////////////////// 479 480 GrEffectRef* SkSweepGradient::asNewEffect(GrContext* context, const SkPaint&) const { 481 SkMatrix matrix; 482 if (!this->getLocalMatrix().invert(&matrix)) { 483 return NULL; 484 } 485 matrix.postConcat(fPtsToUnit); 486 return GrSweepGradient::Create(context, *this, matrix); 487 } 488 489 #else 490 491 GrEffectRef* SkSweepGradient::asNewEffect(GrContext*, const SkPaint&) const { 492 SkDEBUGFAIL("Should not call in GPU-less build"); 493 return NULL; 494 } 495 496 #endif 497 498 #ifdef SK_DEVELOPER 499 void SkSweepGradient::toString(SkString* str) const { 500 str->append("SkSweepGradient: ("); 501 502 str->append("center: ("); 503 str->appendScalar(fCenter.fX); 504 str->append(", "); 505 str->appendScalar(fCenter.fY); 506 str->append(") "); 507 508 this->INHERITED::toString(str); 509 510 str->append(")"); 511 } 512 #endif 513
