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, 12 const Descriptor& desc) 13 : SkGradientShaderBase(desc) 14 , fCenter(SkPoint::Make(cx, cy)) 15 { 16 fPtsToUnit.setTranslate(-cx, -cy); 17 18 // overwrite the tilemode to a canonical value (since sweep ignores it) 19 fTileMode = SkShader::kClamp_TileMode; 20 } 21 22 SkShader::BitmapType SkSweepGradient::asABitmap(SkBitmap* bitmap, 23 SkMatrix* matrix, SkShader::TileMode* xy) const { 24 if (bitmap) { 25 this->getGradientTableBitmap(bitmap); 26 } 27 if (matrix) { 28 *matrix = fPtsToUnit; 29 } 30 if (xy) { 31 xy[0] = fTileMode; 32 xy[1] = kClamp_TileMode; 33 } 34 return kSweep_BitmapType; 35 } 36 37 SkShader::GradientType SkSweepGradient::asAGradient(GradientInfo* info) const { 38 if (info) { 39 commonAsAGradient(info); 40 info->fPoint[0] = fCenter; 41 } 42 return kSweep_GradientType; 43 } 44 45 SkSweepGradient::SkSweepGradient(SkFlattenableReadBuffer& buffer) 46 : INHERITED(buffer), 47 fCenter(buffer.readPoint()) { 48 } 49 50 void SkSweepGradient::flatten(SkFlattenableWriteBuffer& buffer) const { 51 this->INHERITED::flatten(buffer); 52 buffer.writePoint(fCenter); 53 } 54 55 #ifndef SK_SCALAR_IS_FLOAT 56 #ifdef COMPUTE_SWEEP_TABLE 57 #define PI 3.14159265 58 static bool gSweepTableReady; 59 static uint8_t gSweepTable[65]; 60 61 /* Our table stores precomputed values for atan: [0...1] -> [0..PI/4] 62 We scale the results to [0..32] 63 */ 64 static const uint8_t* build_sweep_table() { 65 if (!gSweepTableReady) { 66 const int N = 65; 67 const double DENOM = N - 1; 68 69 for (int i = 0; i < N; i++) 70 { 71 double arg = i / DENOM; 72 double v = atan(arg); 73 int iv = (int)round(v * DENOM * 2 / PI); 74 // printf("[%d] atan(%g) = %g %d\n", i, arg, v, iv); 75 printf("%d, ", iv); 76 gSweepTable[i] = iv; 77 } 78 gSweepTableReady = true; 79 } 80 return gSweepTable; 81 } 82 #else 83 static const uint8_t gSweepTable[] = { 84 0, 1, 1, 2, 3, 3, 4, 4, 5, 6, 6, 7, 8, 8, 9, 9, 85 10, 11, 11, 12, 12, 13, 13, 14, 15, 15, 16, 16, 17, 17, 18, 18, 86 19, 19, 20, 20, 21, 21, 22, 22, 23, 23, 24, 24, 25, 25, 25, 26, 87 26, 27, 27, 27, 28, 28, 29, 29, 29, 30, 30, 30, 31, 31, 31, 32, 88 32 89 }; 90 static const uint8_t* build_sweep_table() { return gSweepTable; } 91 #endif 92 #endif 93 94 // divide numer/denom, with a bias of 6bits. Assumes numer <= denom 95 // and denom != 0. Since our table is 6bits big (+1), this is a nice fit. 96 // Same as (but faster than) SkFixedDiv(numer, denom) >> 10 97 98 //unsigned div_64(int numer, int denom); 99 #ifndef SK_SCALAR_IS_FLOAT 100 static unsigned div_64(int numer, int denom) { 101 SkASSERT(numer <= denom); 102 SkASSERT(numer > 0); 103 SkASSERT(denom > 0); 104 105 int nbits = SkCLZ(numer); 106 int dbits = SkCLZ(denom); 107 int bits = 6 - nbits + dbits; 108 SkASSERT(bits <= 6); 109 110 if (bits < 0) { // detect underflow 111 return 0; 112 } 113 114 denom <<= dbits - 1; 115 numer <<= nbits - 1; 116 117 unsigned result = 0; 118 119 // do the first one 120 if ((numer -= denom) >= 0) { 121 result = 1; 122 } else { 123 numer += denom; 124 } 125 126 // Now fall into our switch statement if there are more bits to compute 127 if (bits > 0) { 128 // make room for the rest of the answer bits 129 result <<= bits; 130 switch (bits) { 131 case 6: 132 if ((numer = (numer << 1) - denom) >= 0) 133 result |= 32; 134 else 135 numer += denom; 136 case 5: 137 if ((numer = (numer << 1) - denom) >= 0) 138 result |= 16; 139 else 140 numer += denom; 141 case 4: 142 if ((numer = (numer << 1) - denom) >= 0) 143 result |= 8; 144 else 145 numer += denom; 146 case 3: 147 if ((numer = (numer << 1) - denom) >= 0) 148 result |= 4; 149 else 150 numer += denom; 151 case 2: 152 if ((numer = (numer << 1) - denom) >= 0) 153 result |= 2; 154 else 155 numer += denom; 156 case 1: 157 default: // not strictly need, but makes GCC make better ARM code 158 if ((numer = (numer << 1) - denom) >= 0) 159 result |= 1; 160 else 161 numer += denom; 162 } 163 } 164 return result; 165 } 166 #endif 167 168 // Given x,y in the first quadrant, return 0..63 for the angle [0..90] 169 #ifndef SK_SCALAR_IS_FLOAT 170 static unsigned atan_0_90(SkFixed y, SkFixed x) { 171 #ifdef SK_DEBUG 172 { 173 static bool gOnce; 174 if (!gOnce) { 175 gOnce = true; 176 SkASSERT(div_64(55, 55) == 64); 177 SkASSERT(div_64(128, 256) == 32); 178 SkASSERT(div_64(2326528, 4685824) == 31); 179 SkASSERT(div_64(753664, 5210112) == 9); 180 SkASSERT(div_64(229376, 4882432) == 3); 181 SkASSERT(div_64(2, 64) == 2); 182 SkASSERT(div_64(1, 64) == 1); 183 // test that we handle underflow correctly 184 SkASSERT(div_64(12345, 0x54321234) == 0); 185 } 186 } 187 #endif 188 189 SkASSERT(y > 0 && x > 0); 190 const uint8_t* table = build_sweep_table(); 191 192 unsigned result; 193 bool swap = (x < y); 194 if (swap) { 195 // first part of the atan(v) = PI/2 - atan(1/v) identity 196 // since our div_64 and table want v <= 1, where v = y/x 197 SkTSwap<SkFixed>(x, y); 198 } 199 200 result = div_64(y, x); 201 202 #ifdef SK_DEBUG 203 { 204 unsigned result2 = SkDivBits(y, x, 6); 205 SkASSERT(result2 == result || 206 (result == 1 && result2 == 0)); 207 } 208 #endif 209 210 SkASSERT(result < SK_ARRAY_COUNT(gSweepTable)); 211 result = table[result]; 212 213 if (swap) { 214 // complete the atan(v) = PI/2 - atan(1/v) identity 215 result = 64 - result; 216 // pin to 63 217 result -= result >> 6; 218 } 219 220 SkASSERT(result <= 63); 221 return result; 222 } 223 #endif 224 225 // returns angle in a circle [0..2PI) -> [0..255] 226 #ifdef SK_SCALAR_IS_FLOAT 227 static unsigned SkATan2_255(float y, float x) { 228 // static const float g255Over2PI = 255 / (2 * SK_ScalarPI); 229 static const float g255Over2PI = 40.584510488433314f; 230 231 float result = sk_float_atan2(y, x); 232 if (result < 0) { 233 result += 2 * SK_ScalarPI; 234 } 235 SkASSERT(result >= 0); 236 // since our value is always >= 0, we can cast to int, which is faster than 237 // calling floorf() 238 int ir = (int)(result * g255Over2PI); 239 SkASSERT(ir >= 0 && ir <= 255); 240 return ir; 241 } 242 #else 243 static unsigned SkATan2_255(SkFixed y, SkFixed x) { 244 if (x == 0) { 245 if (y == 0) { 246 return 0; 247 } 248 return y < 0 ? 192 : 64; 249 } 250 if (y == 0) { 251 return x < 0 ? 128 : 0; 252 } 253 254 /* Find the right quadrant for x,y 255 Since atan_0_90 only handles the first quadrant, we rotate x,y 256 appropriately before calling it, and then add the right amount 257 to account for the real quadrant. 258 quadrant 0 : add 0 | x > 0 && y > 0 259 quadrant 1 : add 64 (90 degrees) | x < 0 && y > 0 260 quadrant 2 : add 128 (180 degrees) | x < 0 && y < 0 261 quadrant 3 : add 192 (270 degrees) | x > 0 && y < 0 262 263 map x<0 to (1 << 6) 264 map y<0 to (3 << 6) 265 add = map_x ^ map_y 266 */ 267 int xsign = x >> 31; 268 int ysign = y >> 31; 269 int add = ((-xsign) ^ (ysign & 3)) << 6; 270 271 #ifdef SK_DEBUG 272 if (0 == add) 273 SkASSERT(x > 0 && y > 0); 274 else if (64 == add) 275 SkASSERT(x < 0 && y > 0); 276 else if (128 == add) 277 SkASSERT(x < 0 && y < 0); 278 else if (192 == add) 279 SkASSERT(x > 0 && y < 0); 280 else 281 SkDEBUGFAIL("bad value for add"); 282 #endif 283 284 /* This ^ trick makes x, y positive, and the swap<> handles quadrants 285 where we need to rotate x,y by 90 or -90 286 */ 287 x = (x ^ xsign) - xsign; 288 y = (y ^ ysign) - ysign; 289 if (add & 64) { // quads 1 or 3 need to swap x,y 290 SkTSwap<SkFixed>(x, y); 291 } 292 293 unsigned result = add + atan_0_90(y, x); 294 SkASSERT(result < 256); 295 return result; 296 } 297 #endif 298 299 void SkSweepGradient::shadeSpan(int x, int y, SkPMColor* SK_RESTRICT dstC, 300 int count) { 301 SkMatrix::MapXYProc proc = fDstToIndexProc; 302 const SkMatrix& matrix = fDstToIndex; 303 const SkPMColor* SK_RESTRICT cache = this->getCache32(); 304 int toggle = init_dither_toggle(x, y); 305 SkPoint srcPt; 306 307 if (fDstToIndexClass != kPerspective_MatrixClass) { 308 proc(matrix, SkIntToScalar(x) + SK_ScalarHalf, 309 SkIntToScalar(y) + SK_ScalarHalf, &srcPt); 310 SkScalar dx, fx = srcPt.fX; 311 SkScalar dy, fy = srcPt.fY; 312 313 if (fDstToIndexClass == kFixedStepInX_MatrixClass) { 314 SkFixed storage[2]; 315 (void)matrix.fixedStepInX(SkIntToScalar(y) + SK_ScalarHalf, 316 &storage[0], &storage[1]); 317 dx = SkFixedToScalar(storage[0]); 318 dy = SkFixedToScalar(storage[1]); 319 } else { 320 SkASSERT(fDstToIndexClass == kLinear_MatrixClass); 321 dx = matrix.getScaleX(); 322 dy = matrix.getSkewY(); 323 } 324 325 for (; count > 0; --count) { 326 *dstC++ = cache[toggle + SkATan2_255(fy, fx)]; 327 fx += dx; 328 fy += dy; 329 toggle = next_dither_toggle(toggle); 330 } 331 } else { // perspective case 332 for (int stop = x + count; x < stop; x++) { 333 proc(matrix, SkIntToScalar(x) + SK_ScalarHalf, 334 SkIntToScalar(y) + SK_ScalarHalf, &srcPt); 335 *dstC++ = cache[toggle + SkATan2_255(srcPt.fY, srcPt.fX)]; 336 toggle = next_dither_toggle(toggle); 337 } 338 } 339 } 340 341 void SkSweepGradient::shadeSpan16(int x, int y, uint16_t* SK_RESTRICT dstC, 342 int count) { 343 SkMatrix::MapXYProc proc = fDstToIndexProc; 344 const SkMatrix& matrix = fDstToIndex; 345 const uint16_t* SK_RESTRICT cache = this->getCache16(); 346 int toggle = init_dither_toggle16(x, y); 347 SkPoint srcPt; 348 349 if (fDstToIndexClass != kPerspective_MatrixClass) { 350 proc(matrix, SkIntToScalar(x) + SK_ScalarHalf, 351 SkIntToScalar(y) + SK_ScalarHalf, &srcPt); 352 SkScalar dx, fx = srcPt.fX; 353 SkScalar dy, fy = srcPt.fY; 354 355 if (fDstToIndexClass == kFixedStepInX_MatrixClass) { 356 SkFixed storage[2]; 357 (void)matrix.fixedStepInX(SkIntToScalar(y) + SK_ScalarHalf, 358 &storage[0], &storage[1]); 359 dx = SkFixedToScalar(storage[0]); 360 dy = SkFixedToScalar(storage[1]); 361 } else { 362 SkASSERT(fDstToIndexClass == kLinear_MatrixClass); 363 dx = matrix.getScaleX(); 364 dy = matrix.getSkewY(); 365 } 366 367 for (; count > 0; --count) { 368 int index = SkATan2_255(fy, fx) >> (8 - kCache16Bits); 369 *dstC++ = cache[toggle + index]; 370 toggle = next_dither_toggle16(toggle); 371 fx += dx; 372 fy += dy; 373 } 374 } else { // perspective case 375 for (int stop = x + count; x < stop; x++) { 376 proc(matrix, SkIntToScalar(x) + SK_ScalarHalf, 377 SkIntToScalar(y) + SK_ScalarHalf, &srcPt); 378 379 int index = SkATan2_255(srcPt.fY, srcPt.fX); 380 index >>= (8 - kCache16Bits); 381 *dstC++ = cache[toggle + index]; 382 toggle = next_dither_toggle16(toggle); 383 } 384 } 385 } 386 387 ///////////////////////////////////////////////////////////////////// 388 389 #if SK_SUPPORT_GPU 390 391 #include "GrTBackendEffectFactory.h" 392 393 class GrGLSweepGradient : public GrGLGradientEffect { 394 public: 395 396 GrGLSweepGradient(const GrBackendEffectFactory& factory, 397 const GrDrawEffect&) : INHERITED (factory) { } 398 virtual ~GrGLSweepGradient() { } 399 400 virtual void emitCode(GrGLShaderBuilder*, 401 const GrDrawEffect&, 402 EffectKey, 403 const char* outputColor, 404 const char* inputColor, 405 const TransformedCoordsArray&, 406 const TextureSamplerArray&) SK_OVERRIDE; 407 408 static EffectKey GenKey(const GrDrawEffect& drawEffect, const GrGLCaps&) { 409 return GenBaseGradientKey(drawEffect); 410 } 411 412 private: 413 414 typedef GrGLGradientEffect INHERITED; 415 416 }; 417 418 ///////////////////////////////////////////////////////////////////// 419 420 class GrSweepGradient : public GrGradientEffect { 421 public: 422 static GrEffectRef* Create(GrContext* ctx, 423 const SkSweepGradient& shader, 424 const SkMatrix& matrix) { 425 AutoEffectUnref effect(SkNEW_ARGS(GrSweepGradient, (ctx, shader, matrix))); 426 return CreateEffectRef(effect); 427 } 428 virtual ~GrSweepGradient() { } 429 430 static const char* Name() { return "Sweep Gradient"; } 431 virtual const GrBackendEffectFactory& getFactory() const SK_OVERRIDE { 432 return GrTBackendEffectFactory<GrSweepGradient>::getInstance(); 433 } 434 435 typedef GrGLSweepGradient GLEffect; 436 437 private: 438 GrSweepGradient(GrContext* ctx, 439 const SkSweepGradient& shader, 440 const SkMatrix& matrix) 441 : INHERITED(ctx, shader, matrix, SkShader::kClamp_TileMode) { } 442 GR_DECLARE_EFFECT_TEST; 443 444 typedef GrGradientEffect INHERITED; 445 }; 446 447 ///////////////////////////////////////////////////////////////////// 448 449 GR_DEFINE_EFFECT_TEST(GrSweepGradient); 450 451 GrEffectRef* GrSweepGradient::TestCreate(SkRandom* random, 452 GrContext* context, 453 const GrDrawTargetCaps&, 454 GrTexture**) { 455 SkPoint center = {random->nextUScalar1(), random->nextUScalar1()}; 456 457 SkColor colors[kMaxRandomGradientColors]; 458 SkScalar stopsArray[kMaxRandomGradientColors]; 459 SkScalar* stops = stopsArray; 460 SkShader::TileMode tmIgnored; 461 int colorCount = RandomGradientParams(random, colors, &stops, &tmIgnored); 462 SkAutoTUnref<SkShader> shader(SkGradientShader::CreateSweep(center.fX, center.fY, 463 colors, stops, colorCount)); 464 SkPaint paint; 465 return shader->asNewEffect(context, paint); 466 } 467 468 ///////////////////////////////////////////////////////////////////// 469 470 void GrGLSweepGradient::emitCode(GrGLShaderBuilder* builder, 471 const GrDrawEffect&, 472 EffectKey key, 473 const char* outputColor, 474 const char* inputColor, 475 const TransformedCoordsArray& coords, 476 const TextureSamplerArray& samplers) { 477 this->emitUniforms(builder, key); 478 SkString coords2D = builder->ensureFSCoords2D(coords, 0); 479 SkString t; 480 t.printf("atan(- %s.y, - %s.x) * 0.1591549430918 + 0.5", coords2D.c_str(), coords2D.c_str()); 481 this->emitColor(builder, t.c_str(), key, 482 outputColor, inputColor, samplers); 483 } 484 485 ///////////////////////////////////////////////////////////////////// 486 487 GrEffectRef* SkSweepGradient::asNewEffect(GrContext* context, const SkPaint&) const { 488 SkMatrix matrix; 489 if (!this->getLocalMatrix().invert(&matrix)) { 490 return NULL; 491 } 492 matrix.postConcat(fPtsToUnit); 493 return GrSweepGradient::Create(context, *this, matrix); 494 } 495 496 #else 497 498 GrEffectRef* SkSweepGradient::asNewEffect(GrContext*, const SkPaint&) const { 499 SkDEBUGFAIL("Should not call in GPU-less build"); 500 return NULL; 501 } 502 503 #endif 504 505 #ifdef SK_DEVELOPER 506 void SkSweepGradient::toString(SkString* str) const { 507 str->append("SkSweepGradient: ("); 508 509 str->append("center: ("); 510 str->appendScalar(fCenter.fX); 511 str->append(", "); 512 str->appendScalar(fCenter.fY); 513 str->append(") "); 514 515 this->INHERITED::toString(str); 516 517 str->append(")"); 518 } 519 #endif 520
