/*
* Copyright 2012 Google Inc.
*
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
*/
#include "SkSweepGradient.h"
SkSweepGradient::SkSweepGradient(SkScalar cx, SkScalar cy,
const Descriptor& desc)
: SkGradientShaderBase(desc)
, fCenter(SkPoint::Make(cx, cy))
{
fPtsToUnit.setTranslate(-cx, -cy);
// overwrite the tilemode to a canonical value (since sweep ignores it)
fTileMode = SkShader::kClamp_TileMode;
}
SkShader::BitmapType SkSweepGradient::asABitmap(SkBitmap* bitmap,
SkMatrix* matrix, SkShader::TileMode* xy) const {
if (bitmap) {
this->getGradientTableBitmap(bitmap);
}
if (matrix) {
*matrix = fPtsToUnit;
}
if (xy) {
xy[0] = fTileMode;
xy[1] = kClamp_TileMode;
}
return kSweep_BitmapType;
}
SkShader::GradientType SkSweepGradient::asAGradient(GradientInfo* info) const {
if (info) {
commonAsAGradient(info);
info->fPoint[0] = fCenter;
}
return kSweep_GradientType;
}
SkSweepGradient::SkSweepGradient(SkFlattenableReadBuffer& buffer)
: INHERITED(buffer),
fCenter(buffer.readPoint()) {
}
void SkSweepGradient::flatten(SkFlattenableWriteBuffer& buffer) const {
this->INHERITED::flatten(buffer);
buffer.writePoint(fCenter);
}
#ifndef SK_SCALAR_IS_FLOAT
#ifdef COMPUTE_SWEEP_TABLE
#define PI 3.14159265
static bool gSweepTableReady;
static uint8_t gSweepTable[65];
/* Our table stores precomputed values for atan: [0...1] -> [0..PI/4]
We scale the results to [0..32]
*/
static const uint8_t* build_sweep_table() {
if (!gSweepTableReady) {
const int N = 65;
const double DENOM = N - 1;
for (int i = 0; i < N; i++)
{
double arg = i / DENOM;
double v = atan(arg);
int iv = (int)round(v * DENOM * 2 / PI);
// printf("[%d] atan(%g) = %g %d\n", i, arg, v, iv);
printf("%d, ", iv);
gSweepTable[i] = iv;
}
gSweepTableReady = true;
}
return gSweepTable;
}
#else
static const uint8_t gSweepTable[] = {
0, 1, 1, 2, 3, 3, 4, 4, 5, 6, 6, 7, 8, 8, 9, 9,
10, 11, 11, 12, 12, 13, 13, 14, 15, 15, 16, 16, 17, 17, 18, 18,
19, 19, 20, 20, 21, 21, 22, 22, 23, 23, 24, 24, 25, 25, 25, 26,
26, 27, 27, 27, 28, 28, 29, 29, 29, 30, 30, 30, 31, 31, 31, 32,
32
};
static const uint8_t* build_sweep_table() { return gSweepTable; }
#endif
#endif
// divide numer/denom, with a bias of 6bits. Assumes numer <= denom
// and denom != 0. Since our table is 6bits big (+1), this is a nice fit.
// Same as (but faster than) SkFixedDiv(numer, denom) >> 10
//unsigned div_64(int numer, int denom);
#ifndef SK_SCALAR_IS_FLOAT
static unsigned div_64(int numer, int denom) {
SkASSERT(numer <= denom);
SkASSERT(numer > 0);
SkASSERT(denom > 0);
int nbits = SkCLZ(numer);
int dbits = SkCLZ(denom);
int bits = 6 - nbits + dbits;
SkASSERT(bits <= 6);
if (bits < 0) { // detect underflow
return 0;
}
denom <<= dbits - 1;
numer <<= nbits - 1;
unsigned result = 0;
// do the first one
if ((numer -= denom) >= 0) {
result = 1;
} else {
numer += denom;
}
// Now fall into our switch statement if there are more bits to compute
if (bits > 0) {
// make room for the rest of the answer bits
result <<= bits;
switch (bits) {
case 6:
if ((numer = (numer << 1) - denom) >= 0)
result |= 32;
else
numer += denom;
case 5:
if ((numer = (numer << 1) - denom) >= 0)
result |= 16;
else
numer += denom;
case 4:
if ((numer = (numer << 1) - denom) >= 0)
result |= 8;
else
numer += denom;
case 3:
if ((numer = (numer << 1) - denom) >= 0)
result |= 4;
else
numer += denom;
case 2:
if ((numer = (numer << 1) - denom) >= 0)
result |= 2;
else
numer += denom;
case 1:
default: // not strictly need, but makes GCC make better ARM code
if ((numer = (numer << 1) - denom) >= 0)
result |= 1;
else
numer += denom;
}
}
return result;
}
#endif
// Given x,y in the first quadrant, return 0..63 for the angle [0..90]
#ifndef SK_SCALAR_IS_FLOAT
static unsigned atan_0_90(SkFixed y, SkFixed x) {
#ifdef SK_DEBUG
{
static bool gOnce;
if (!gOnce) {
gOnce = true;
SkASSERT(div_64(55, 55) == 64);
SkASSERT(div_64(128, 256) == 32);
SkASSERT(div_64(2326528, 4685824) == 31);
SkASSERT(div_64(753664, 5210112) == 9);
SkASSERT(div_64(229376, 4882432) == 3);
SkASSERT(div_64(2, 64) == 2);
SkASSERT(div_64(1, 64) == 1);
// test that we handle underflow correctly
SkASSERT(div_64(12345, 0x54321234) == 0);
}
}
#endif
SkASSERT(y > 0 && x > 0);
const uint8_t* table = build_sweep_table();
unsigned result;
bool swap = (x < y);
if (swap) {
// first part of the atan(v) = PI/2 - atan(1/v) identity
// since our div_64 and table want v <= 1, where v = y/x
SkTSwap<SkFixed>(x, y);
}
result = div_64(y, x);
#ifdef SK_DEBUG
{
unsigned result2 = SkDivBits(y, x, 6);
SkASSERT(result2 == result ||
(result == 1 && result2 == 0));
}
#endif
SkASSERT(result < SK_ARRAY_COUNT(gSweepTable));
result = table[result];
if (swap) {
// complete the atan(v) = PI/2 - atan(1/v) identity
result = 64 - result;
// pin to 63
result -= result >> 6;
}
SkASSERT(result <= 63);
return result;
}
#endif
// returns angle in a circle [0..2PI) -> [0..255]
#ifdef SK_SCALAR_IS_FLOAT
static unsigned SkATan2_255(float y, float x) {
// static const float g255Over2PI = 255 / (2 * SK_ScalarPI);
static const float g255Over2PI = 40.584510488433314f;
float result = sk_float_atan2(y, x);
if (result < 0) {
result += 2 * SK_ScalarPI;
}
SkASSERT(result >= 0);
// since our value is always >= 0, we can cast to int, which is faster than
// calling floorf()
int ir = (int)(result * g255Over2PI);
SkASSERT(ir >= 0 && ir <= 255);
return ir;
}
#else
static unsigned SkATan2_255(SkFixed y, SkFixed x) {
if (x == 0) {
if (y == 0) {
return 0;
}
return y < 0 ? 192 : 64;
}
if (y == 0) {
return x < 0 ? 128 : 0;
}
/* Find the right quadrant for x,y
Since atan_0_90 only handles the first quadrant, we rotate x,y
appropriately before calling it, and then add the right amount
to account for the real quadrant.
quadrant 0 : add 0 | x > 0 && y > 0
quadrant 1 : add 64 (90 degrees) | x < 0 && y > 0
quadrant 2 : add 128 (180 degrees) | x < 0 && y < 0
quadrant 3 : add 192 (270 degrees) | x > 0 && y < 0
map x<0 to (1 << 6)
map y<0 to (3 << 6)
add = map_x ^ map_y
*/
int xsign = x >> 31;
int ysign = y >> 31;
int add = ((-xsign) ^ (ysign & 3)) << 6;
#ifdef SK_DEBUG
if (0 == add)
SkASSERT(x > 0 && y > 0);
else if (64 == add)
SkASSERT(x < 0 && y > 0);
else if (128 == add)
SkASSERT(x < 0 && y < 0);
else if (192 == add)
SkASSERT(x > 0 && y < 0);
else
SkDEBUGFAIL("bad value for add");
#endif
/* This ^ trick makes x, y positive, and the swap<> handles quadrants
where we need to rotate x,y by 90 or -90
*/
x = (x ^ xsign) - xsign;
y = (y ^ ysign) - ysign;
if (add & 64) { // quads 1 or 3 need to swap x,y
SkTSwap<SkFixed>(x, y);
}
unsigned result = add + atan_0_90(y, x);
SkASSERT(result < 256);
return result;
}
#endif
void SkSweepGradient::shadeSpan(int x, int y, SkPMColor* SK_RESTRICT dstC,
int count) {
SkMatrix::MapXYProc proc = fDstToIndexProc;
const SkMatrix& matrix = fDstToIndex;
const SkPMColor* SK_RESTRICT cache = this->getCache32();
int toggle = init_dither_toggle(x, y);
SkPoint srcPt;
if (fDstToIndexClass != kPerspective_MatrixClass) {
proc(matrix, SkIntToScalar(x) + SK_ScalarHalf,
SkIntToScalar(y) + SK_ScalarHalf, &srcPt);
SkScalar dx, fx = srcPt.fX;
SkScalar dy, fy = srcPt.fY;
if (fDstToIndexClass == kFixedStepInX_MatrixClass) {
SkFixed storage[2];
(void)matrix.fixedStepInX(SkIntToScalar(y) + SK_ScalarHalf,
&storage[0], &storage[1]);
dx = SkFixedToScalar(storage[0]);
dy = SkFixedToScalar(storage[1]);
} else {
SkASSERT(fDstToIndexClass == kLinear_MatrixClass);
dx = matrix.getScaleX();
dy = matrix.getSkewY();
}
for (; count > 0; --count) {
*dstC++ = cache[toggle + SkATan2_255(fy, fx)];
fx += dx;
fy += dy;
toggle = next_dither_toggle(toggle);
}
} else { // perspective case
for (int stop = x + count; x < stop; x++) {
proc(matrix, SkIntToScalar(x) + SK_ScalarHalf,
SkIntToScalar(y) + SK_ScalarHalf, &srcPt);
*dstC++ = cache[toggle + SkATan2_255(srcPt.fY, srcPt.fX)];
toggle = next_dither_toggle(toggle);
}
}
}
void SkSweepGradient::shadeSpan16(int x, int y, uint16_t* SK_RESTRICT dstC,
int count) {
SkMatrix::MapXYProc proc = fDstToIndexProc;
const SkMatrix& matrix = fDstToIndex;
const uint16_t* SK_RESTRICT cache = this->getCache16();
int toggle = init_dither_toggle16(x, y);
SkPoint srcPt;
if (fDstToIndexClass != kPerspective_MatrixClass) {
proc(matrix, SkIntToScalar(x) + SK_ScalarHalf,
SkIntToScalar(y) + SK_ScalarHalf, &srcPt);
SkScalar dx, fx = srcPt.fX;
SkScalar dy, fy = srcPt.fY;
if (fDstToIndexClass == kFixedStepInX_MatrixClass) {
SkFixed storage[2];
(void)matrix.fixedStepInX(SkIntToScalar(y) + SK_ScalarHalf,
&storage[0], &storage[1]);
dx = SkFixedToScalar(storage[0]);
dy = SkFixedToScalar(storage[1]);
} else {
SkASSERT(fDstToIndexClass == kLinear_MatrixClass);
dx = matrix.getScaleX();
dy = matrix.getSkewY();
}
for (; count > 0; --count) {
int index = SkATan2_255(fy, fx) >> (8 - kCache16Bits);
*dstC++ = cache[toggle + index];
toggle = next_dither_toggle16(toggle);
fx += dx;
fy += dy;
}
} else { // perspective case
for (int stop = x + count; x < stop; x++) {
proc(matrix, SkIntToScalar(x) + SK_ScalarHalf,
SkIntToScalar(y) + SK_ScalarHalf, &srcPt);
int index = SkATan2_255(srcPt.fY, srcPt.fX);
index >>= (8 - kCache16Bits);
*dstC++ = cache[toggle + index];
toggle = next_dither_toggle16(toggle);
}
}
}
/////////////////////////////////////////////////////////////////////
#if SK_SUPPORT_GPU
#include "GrTBackendEffectFactory.h"
class GrGLSweepGradient : public GrGLGradientEffect {
public:
GrGLSweepGradient(const GrBackendEffectFactory& factory,
const GrDrawEffect&) : INHERITED (factory) { }
virtual ~GrGLSweepGradient() { }
virtual void emitCode(GrGLShaderBuilder*,
const GrDrawEffect&,
EffectKey,
const char* outputColor,
const char* inputColor,
const TransformedCoordsArray&,
const TextureSamplerArray&) SK_OVERRIDE;
static EffectKey GenKey(const GrDrawEffect& drawEffect, const GrGLCaps&) {
return GenBaseGradientKey(drawEffect);
}
private:
typedef GrGLGradientEffect INHERITED;
};
/////////////////////////////////////////////////////////////////////
class GrSweepGradient : public GrGradientEffect {
public:
static GrEffectRef* Create(GrContext* ctx,
const SkSweepGradient& shader,
const SkMatrix& matrix) {
AutoEffectUnref effect(SkNEW_ARGS(GrSweepGradient, (ctx, shader, matrix)));
return CreateEffectRef(effect);
}
virtual ~GrSweepGradient() { }
static const char* Name() { return "Sweep Gradient"; }
virtual const GrBackendEffectFactory& getFactory() const SK_OVERRIDE {
return GrTBackendEffectFactory<GrSweepGradient>::getInstance();
}
typedef GrGLSweepGradient GLEffect;
private:
GrSweepGradient(GrContext* ctx,
const SkSweepGradient& shader,
const SkMatrix& matrix)
: INHERITED(ctx, shader, matrix, SkShader::kClamp_TileMode) { }
GR_DECLARE_EFFECT_TEST;
typedef GrGradientEffect INHERITED;
};
/////////////////////////////////////////////////////////////////////
GR_DEFINE_EFFECT_TEST(GrSweepGradient);
GrEffectRef* GrSweepGradient::TestCreate(SkRandom* random,
GrContext* context,
const GrDrawTargetCaps&,
GrTexture**) {
SkPoint center = {random->nextUScalar1(), random->nextUScalar1()};
SkColor colors[kMaxRandomGradientColors];
SkScalar stopsArray[kMaxRandomGradientColors];
SkScalar* stops = stopsArray;
SkShader::TileMode tmIgnored;
int colorCount = RandomGradientParams(random, colors, &stops, &tmIgnored);
SkAutoTUnref<SkShader> shader(SkGradientShader::CreateSweep(center.fX, center.fY,
colors, stops, colorCount));
SkPaint paint;
return shader->asNewEffect(context, paint);
}
/////////////////////////////////////////////////////////////////////
void GrGLSweepGradient::emitCode(GrGLShaderBuilder* builder,
const GrDrawEffect&,
EffectKey key,
const char* outputColor,
const char* inputColor,
const TransformedCoordsArray& coords,
const TextureSamplerArray& samplers) {
this->emitUniforms(builder, key);
SkString coords2D = builder->ensureFSCoords2D(coords, 0);
SkString t;
t.printf("atan(- %s.y, - %s.x) * 0.1591549430918 + 0.5", coords2D.c_str(), coords2D.c_str());
this->emitColor(builder, t.c_str(), key,
outputColor, inputColor, samplers);
}
/////////////////////////////////////////////////////////////////////
GrEffectRef* SkSweepGradient::asNewEffect(GrContext* context, const SkPaint&) const {
SkMatrix matrix;
if (!this->getLocalMatrix().invert(&matrix)) {
return NULL;
}
matrix.postConcat(fPtsToUnit);
return GrSweepGradient::Create(context, *this, matrix);
}
#else
GrEffectRef* SkSweepGradient::asNewEffect(GrContext*, const SkPaint&) const {
SkDEBUGFAIL("Should not call in GPU-less build");
return NULL;
}
#endif
#ifdef SK_DEVELOPER
void SkSweepGradient::toString(SkString* str) const {
str->append("SkSweepGradient: (");
str->append("center: (");
str->appendScalar(fCenter.fX);
str->append(", ");
str->appendScalar(fCenter.fY);
str->append(") ");
this->INHERITED::toString(str);
str->append(")");
}
#endif