/*
* Copyright 2016 Google Inc.
*
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
*/
#ifndef SkLinearBitmapPipeline_sampler_DEFINED
#define SkLinearBitmapPipeline_sampler_DEFINED
#include <tuple>
#include "SkAutoMalloc.h"
#include "SkColor.h"
#include "SkColorPriv.h"
#include "SkFixed.h" // for SkFixed1 only. Don't use SkFixed in this file.
#include "SkHalf.h"
#include "SkLinearBitmapPipeline_core.h"
#include "SkNx.h"
#include "SkPM4fPriv.h"
namespace {
// Explaination of the math:
// 1 - x x
// +--------+--------+
// | | |
// 1 - y | px00 | px10 |
// | | |
// +--------+--------+
// | | |
// y | px01 | px11 |
// | | |
// +--------+--------+
//
//
// Given a pixelxy each is multiplied by a different factor derived from the fractional part of x
// and y:
// * px00 -> (1 - x)(1 - y) = 1 - x - y + xy
// * px10 -> x(1 - y) = x - xy
// * px01 -> (1 - x)y = y - xy
// * px11 -> xy
// So x * y is calculated first and then used to calculate all the other factors.
static Sk4s SK_VECTORCALL bilerp4(Sk4s xs, Sk4s ys, Sk4f px00, Sk4f px10,
Sk4f px01, Sk4f px11) {
// Calculate fractional xs and ys.
Sk4s fxs = xs - xs.floor();
Sk4s fys = ys - ys.floor();
Sk4s fxys{fxs * fys};
Sk4f sum = px11 * fxys;
sum = sum + px01 * (fys - fxys);
sum = sum + px10 * (fxs - fxys);
sum = sum + px00 * (Sk4f{1.0f} - fxs - fys + fxys);
return sum;
}
////////////////////////////////////////////////////////////////////////////////////////////////////
// PixelGetter is the lowest level interface to the source data. There is a PixelConverter for each
// of the different SkColorTypes.
template <SkColorType, SkGammaType> class PixelConverter;
// Alpha handling:
// The alpha from the paint (tintColor) is used in the blend part of the pipeline to modulate
// the entire bitmap. So, the tint color is given an alpha of 1.0 so that the later alpha can
// modulate this color later.
template <>
class PixelConverter<kAlpha_8_SkColorType, kLinear_SkGammaType> {
public:
using Element = uint8_t;
PixelConverter(const SkPixmap& srcPixmap, SkColor tintColor) {
fTintColor = SkColor4f::FromColor(tintColor);
fTintColor.fA = 1.0f;
}
Sk4f toSk4f(const Element pixel) const {
return Sk4f::Load(&fTintColor) * (pixel * (1.0f/255.0f));
}
private:
SkColor4f fTintColor;
};
template <SkGammaType gammaType>
static inline Sk4f pmcolor_to_rgba(SkPMColor pixel) {
return swizzle_rb_if_bgra(
(gammaType == kSRGB_SkGammaType) ? Sk4f_fromS32(pixel)
: Sk4f_fromL32(pixel));
}
template <SkGammaType gammaType>
class PixelConverter<kRGB_565_SkColorType, gammaType> {
public:
using Element = uint16_t;
PixelConverter(const SkPixmap& srcPixmap) { }
Sk4f toSk4f(Element pixel) const {
return pmcolor_to_rgba<gammaType>(SkPixel16ToPixel32(pixel));
}
};
template <SkGammaType gammaType>
class PixelConverter<kARGB_4444_SkColorType, gammaType> {
public:
using Element = uint16_t;
PixelConverter(const SkPixmap& srcPixmap) { }
Sk4f toSk4f(Element pixel) const {
return pmcolor_to_rgba<gammaType>(SkPixel4444ToPixel32(pixel));
}
};
template <SkGammaType gammaType>
class PixelConverter<kRGBA_8888_SkColorType, gammaType> {
public:
using Element = uint32_t;
PixelConverter(const SkPixmap& srcPixmap) { }
Sk4f toSk4f(Element pixel) const {
return gammaType == kSRGB_SkGammaType
? Sk4f_fromS32(pixel)
: Sk4f_fromL32(pixel);
}
};
template <SkGammaType gammaType>
class PixelConverter<kBGRA_8888_SkColorType, gammaType> {
public:
using Element = uint32_t;
PixelConverter(const SkPixmap& srcPixmap) { }
Sk4f toSk4f(Element pixel) const {
return swizzle_rb(
gammaType == kSRGB_SkGammaType ? Sk4f_fromS32(pixel) : Sk4f_fromL32(pixel));
}
};
template <SkGammaType gammaType>
class PixelConverter<kIndex_8_SkColorType, gammaType> {
public:
using Element = uint8_t;
PixelConverter(const SkPixmap& srcPixmap)
: fColorTableSize(srcPixmap.ctable()->count()){
SkColorTable* skColorTable = srcPixmap.ctable();
SkASSERT(skColorTable != nullptr);
fColorTable = (Sk4f*)SkAlign16((intptr_t)fColorTableStorage.get());
for (int i = 0; i < fColorTableSize; i++) {
fColorTable[i] = pmcolor_to_rgba<gammaType>((*skColorTable)[i]);
}
}
PixelConverter(const PixelConverter& strategy)
: fColorTableSize{strategy.fColorTableSize}{
fColorTable = (Sk4f*)SkAlign16((intptr_t)fColorTableStorage.get());
for (int i = 0; i < fColorTableSize; i++) {
fColorTable[i] = strategy.fColorTable[i];
}
}
Sk4f toSk4f(Element index) const {
return fColorTable[index];
}
private:
static const size_t kColorTableSize = sizeof(Sk4f[256]) + 12;
const int fColorTableSize;
SkAutoMalloc fColorTableStorage{kColorTableSize};
Sk4f* fColorTable;
};
template <SkGammaType gammaType>
class PixelConverter<kGray_8_SkColorType, gammaType> {
public:
using Element = uint8_t;
PixelConverter(const SkPixmap& srcPixmap) { }
Sk4f toSk4f(Element pixel) const {
float gray = (gammaType == kSRGB_SkGammaType)
? sk_linear_from_srgb[pixel]
: pixel * (1/255.0f);
return {gray, gray, gray, 1.0f};
}
};
template <>
class PixelConverter<kRGBA_F16_SkColorType, kLinear_SkGammaType> {
public:
using Element = uint64_t;
PixelConverter(const SkPixmap& srcPixmap) { }
Sk4f toSk4f(const Element pixel) const {
return SkHalfToFloat_finite_ftz(pixel);
}
};
class PixelAccessorShim {
public:
explicit PixelAccessorShim(SkLinearBitmapPipeline::PixelAccessorInterface* accessor)
: fPixelAccessor(accessor) { }
void SK_VECTORCALL getFewPixels(
int n, Sk4i xs, Sk4i ys, Sk4f* px0, Sk4f* px1, Sk4f* px2) const {
fPixelAccessor->getFewPixels(n, xs, ys, px0, px1, px2);
}
void SK_VECTORCALL get4Pixels(
Sk4i xs, Sk4i ys, Sk4f* px0, Sk4f* px1, Sk4f* px2, Sk4f* px3) const {
fPixelAccessor->get4Pixels(xs, ys, px0, px1, px2, px3);
}
void get4Pixels(
const void* src, int index, Sk4f* px0, Sk4f* px1, Sk4f* px2, Sk4f* px3) const {
fPixelAccessor->get4Pixels(src, index, px0, px1, px2, px3);
}
Sk4f getPixelFromRow(const void* row, int index) const {
return fPixelAccessor->getPixelFromRow(row, index);
}
Sk4f getPixelAt(int index) const {
return fPixelAccessor->getPixelAt(index);
}
const void* row(int y) const {
return fPixelAccessor->row(y);
}
private:
SkLinearBitmapPipeline::PixelAccessorInterface* const fPixelAccessor;
};
////////////////////////////////////////////////////////////////////////////////////////////////////
// PixelAccessor handles all the same plumbing for all the PixelGetters.
template <SkColorType colorType, SkGammaType gammaType>
class PixelAccessor final : public SkLinearBitmapPipeline::PixelAccessorInterface {
using Element = typename PixelConverter<colorType, gammaType>::Element;
public:
template <typename... Args>
PixelAccessor(const SkPixmap& srcPixmap, Args&&... args)
: fSrc{static_cast<const Element*>(srcPixmap.addr())}
, fWidth{srcPixmap.rowBytesAsPixels()}
, fConverter{srcPixmap, std::move<Args>(args)...} { }
void SK_VECTORCALL getFewPixels (
int n, Sk4i xs, Sk4i ys, Sk4f* px0, Sk4f* px1, Sk4f* px2) const override {
Sk4i bufferLoc = ys * fWidth + xs;
switch (n) {
case 3:
*px2 = this->getPixelAt(bufferLoc[2]);
case 2:
*px1 = this->getPixelAt(bufferLoc[1]);
case 1:
*px0 = this->getPixelAt(bufferLoc[0]);
default:
break;
}
}
void SK_VECTORCALL get4Pixels(
Sk4i xs, Sk4i ys, Sk4f* px0, Sk4f* px1, Sk4f* px2, Sk4f* px3) const override {
Sk4i bufferLoc = ys * fWidth + xs;
*px0 = this->getPixelAt(bufferLoc[0]);
*px1 = this->getPixelAt(bufferLoc[1]);
*px2 = this->getPixelAt(bufferLoc[2]);
*px3 = this->getPixelAt(bufferLoc[3]);
}
void get4Pixels(
const void* src, int index, Sk4f* px0, Sk4f* px1, Sk4f* px2, Sk4f* px3) const override {
*px0 = this->getPixelFromRow(src, index + 0);
*px1 = this->getPixelFromRow(src, index + 1);
*px2 = this->getPixelFromRow(src, index + 2);
*px3 = this->getPixelFromRow(src, index + 3);
}
Sk4f getPixelFromRow(const void* row, int index) const override {
const Element* src = static_cast<const Element*>(row);
return fConverter.toSk4f(src[index]);
}
Sk4f getPixelAt(int index) const override {
return this->getPixelFromRow(fSrc, index);
}
const void* row(int y) const override { return fSrc + y * fWidth; }
private:
const Element* const fSrc;
const int fWidth;
PixelConverter<colorType, gammaType> fConverter;
};
// We're moving through source space at a rate of 1 source pixel per 1 dst pixel.
// We'll never re-use pixels, but we can at least load contiguous pixels.
template <typename Next, typename Strategy>
static void src_strategy_blend(Span span, Next* next, Strategy* strategy) {
SkPoint start;
SkScalar length;
int count;
std::tie(start, length, count) = span;
int ix = SkScalarFloorToInt(X(start));
const void* row = strategy->row((int)std::floor(Y(start)));
if (length > 0) {
while (count >= 4) {
Sk4f px0, px1, px2, px3;
strategy->get4Pixels(row, ix, &px0, &px1, &px2, &px3);
next->blend4Pixels(px0, px1, px2, px3);
ix += 4;
count -= 4;
}
while (count > 0) {
next->blendPixel(strategy->getPixelFromRow(row, ix));
ix += 1;
count -= 1;
}
} else {
while (count >= 4) {
Sk4f px0, px1, px2, px3;
strategy->get4Pixels(row, ix - 3, &px3, &px2, &px1, &px0);
next->blend4Pixels(px0, px1, px2, px3);
ix -= 4;
count -= 4;
}
while (count > 0) {
next->blendPixel(strategy->getPixelFromRow(row, ix));
ix -= 1;
count -= 1;
}
}
}
// -- NearestNeighborSampler -----------------------------------------------------------------------
// NearestNeighborSampler - use nearest neighbor filtering to create runs of destination pixels.
template<typename Accessor, typename Next>
class NearestNeighborSampler : public SkLinearBitmapPipeline::SampleProcessorInterface {
public:
template<typename... Args>
NearestNeighborSampler(SkLinearBitmapPipeline::BlendProcessorInterface* next, Args&& ... args)
: fNext{next}, fAccessor{std::forward<Args>(args)...} { }
NearestNeighborSampler(SkLinearBitmapPipeline::BlendProcessorInterface* next,
const NearestNeighborSampler& sampler)
: fNext{next}, fAccessor{sampler.fAccessor} { }
void SK_VECTORCALL pointListFew(int n, Sk4s xs, Sk4s ys) override {
SkASSERT(0 < n && n < 4);
Sk4f px0, px1, px2;
fAccessor.getFewPixels(n, SkNx_cast<int>(xs), SkNx_cast<int>(ys), &px0, &px1, &px2);
if (n >= 1) fNext->blendPixel(px0);
if (n >= 2) fNext->blendPixel(px1);
if (n >= 3) fNext->blendPixel(px2);
}
void SK_VECTORCALL pointList4(Sk4s xs, Sk4s ys) override {
Sk4f px0, px1, px2, px3;
fAccessor.get4Pixels(SkNx_cast<int>(xs), SkNx_cast<int>(ys), &px0, &px1, &px2, &px3);
fNext->blend4Pixels(px0, px1, px2, px3);
}
void pointSpan(Span span) override {
SkASSERT(!span.isEmpty());
SkPoint start;
SkScalar length;
int count;
std::tie(start, length, count) = span;
SkScalar absLength = SkScalarAbs(length);
if (absLength < (count - 1)) {
this->spanSlowRate(span);
} else if (absLength == (count - 1)) {
src_strategy_blend(span, fNext, &fAccessor);
} else {
this->spanFastRate(span);
}
}
void repeatSpan(Span span, int32_t repeatCount) override {
while (repeatCount > 0) {
this->pointSpan(span);
repeatCount--;
}
}
private:
// When moving through source space more slowly than dst space (zoomed in),
// we'll be sampling from the same source pixel more than once.
void spanSlowRate(Span span) {
SkPoint start; SkScalar length; int count;
std::tie(start, length, count) = span;
SkScalar x = X(start);
// fx is a fixed 48.16 number.
int64_t fx = static_cast<int64_t>(x * SK_Fixed1);
SkScalar dx = length / (count - 1);
// fdx is a fixed 48.16 number.
int64_t fdx = static_cast<int64_t>(dx * SK_Fixed1);
const void* row = fAccessor.row((int)std::floor(Y(start)));
Next* next = fNext;
int64_t ix = fx >> 16;
int64_t prevIX = ix;
Sk4f fpixel = fAccessor.getPixelFromRow(row, ix);
// When dx is less than one, each pixel is used more than once. Using the fixed point fx
// allows the code to quickly check that the same pixel is being used. The code uses this
// same pixel check to do the sRGB and normalization only once.
auto getNextPixel = [&]() {
if (ix != prevIX) {
fpixel = fAccessor.getPixelFromRow(row, ix);
prevIX = ix;
}
fx += fdx;
ix = fx >> 16;
return fpixel;
};
while (count >= 4) {
Sk4f px0 = getNextPixel();
Sk4f px1 = getNextPixel();
Sk4f px2 = getNextPixel();
Sk4f px3 = getNextPixel();
next->blend4Pixels(px0, px1, px2, px3);
count -= 4;
}
while (count > 0) {
next->blendPixel(getNextPixel());
count -= 1;
}
}
// We're moving through source space at a rate of 1 source pixel per 1 dst pixel.
// We'll never re-use pixels, but we can at least load contiguous pixels.
void spanUnitRate(Span span) {
src_strategy_blend(span, fNext, &fAccessor);
}
// We're moving through source space faster than dst (zoomed out),
// so we'll never reuse a source pixel or be able to do contiguous loads.
void spanFastRate(Span span) {
span_fallback(span, this);
}
Next* const fNext;
Accessor fAccessor;
};
// From an edgeType, the integer value of a pixel vs, and the integer value of the extreme edge
// vMax, take the point which might be off the tile by one pixel and either wrap it or pin it to
// generate the right pixel. The value vs is on the interval [-1, vMax + 1]. It produces a value
// on the interval [0, vMax].
// Note: vMax is not width or height, but width-1 or height-1 because it is the largest valid pixel.
static inline int adjust_edge(SkShader::TileMode edgeType, int vs, int vMax) {
SkASSERT(-1 <= vs && vs <= vMax + 1);
switch (edgeType) {
case SkShader::kClamp_TileMode:
case SkShader::kMirror_TileMode:
vs = std::max(vs, 0);
vs = std::min(vs, vMax);
break;
case SkShader::kRepeat_TileMode:
vs = (vs <= vMax) ? vs : 0;
vs = (vs >= 0) ? vs : vMax;
break;
}
SkASSERT(0 <= vs && vs <= vMax);
return vs;
}
// From a sample point on the tile, return the top or left filter value.
// The result r should be in the range (0, 1]. Since this represents the weight given to the top
// left element, then if x == 0.5 the filter value should be 1.0.
// The input sample point must be on the tile, therefore it must be >= 0.
static SkScalar sample_to_filter(SkScalar x) {
SkASSERT(x >= 0.0f);
// The usual form of the top or left edge is x - .5, but since we are working on the unit
// square, then x + .5 works just as well. This also guarantees that v > 0.0 allowing the use
// of trunc.
SkScalar v = x + 0.5f;
// Produce the top or left offset a value on the range [0, 1).
SkScalar f = v - SkScalarTruncToScalar(v);
// Produce the filter value which is on the range (0, 1].
SkScalar r = 1.0f - f;
SkASSERT(0.0f < r && r <= 1.0f);
return r;
}
// -- BilerpSampler --------------------------------------------------------------------------------
// BilerpSampler - use a bilerp filter to create runs of destination pixels.
// Note: in the code below, there are two types of points
// * sample points - these are the points passed in by pointList* and Spans.
// * filter points - are created from a sample point to form the coordinates of the points
// to use in the filter and to generate the filter values.
template<typename Accessor, typename Next>
class BilerpSampler : public SkLinearBitmapPipeline::SampleProcessorInterface {
public:
template<typename... Args>
BilerpSampler(
SkLinearBitmapPipeline::BlendProcessorInterface* next,
SkISize dimensions,
SkShader::TileMode xTile, SkShader::TileMode yTile,
Args&& ... args
)
: fNext{next}
, fXEdgeType{xTile}
, fXMax{dimensions.width() - 1}
, fYEdgeType{yTile}
, fYMax{dimensions.height() - 1}
, fAccessor{std::forward<Args>(args)...} { }
BilerpSampler(SkLinearBitmapPipeline::BlendProcessorInterface* next,
const BilerpSampler& sampler)
: fNext{next}
, fXEdgeType{sampler.fXEdgeType}
, fXMax{sampler.fXMax}
, fYEdgeType{sampler.fYEdgeType}
, fYMax{sampler.fYMax}
, fAccessor{sampler.fAccessor} { }
void SK_VECTORCALL pointListFew(int n, Sk4s xs, Sk4s ys) override {
SkASSERT(0 < n && n < 4);
auto bilerpPixel = [&](int index) {
return this->bilerpSamplePoint(SkPoint{xs[index], ys[index]});
};
if (n >= 1) fNext->blendPixel(bilerpPixel(0));
if (n >= 2) fNext->blendPixel(bilerpPixel(1));
if (n >= 3) fNext->blendPixel(bilerpPixel(2));
}
void SK_VECTORCALL pointList4(Sk4s xs, Sk4s ys) override {
auto bilerpPixel = [&](int index) {
return this->bilerpSamplePoint(SkPoint{xs[index], ys[index]});
};
fNext->blend4Pixels(bilerpPixel(0), bilerpPixel(1), bilerpPixel(2), bilerpPixel(3));
}
void pointSpan(Span span) override {
SkASSERT(!span.isEmpty());
SkPoint start;
SkScalar length;
int count;
std::tie(start, length, count) = span;
// Nothing to do.
if (count == 0) {
return;
}
// Trivial case. No sample points are generated other than start.
if (count == 1) {
fNext->blendPixel(this->bilerpSamplePoint(start));
return;
}
// Note: the following code could be done in terms of dx = length / (count -1), but that
// would introduce a divide that is not needed for the most common dx == 1 cases.
SkScalar absLength = SkScalarAbs(length);
if (absLength == 0.0f) {
// |dx| == 0
// length is zero, so clamp an edge pixel.
this->spanZeroRate(span);
} else if (absLength < (count - 1)) {
// 0 < |dx| < 1.
this->spanSlowRate(span);
} else if (absLength == (count - 1)) {
// |dx| == 1.
if (sample_to_filter(span.startX()) == 1.0f
&& sample_to_filter(span.startY()) == 1.0f) {
// All the pixels are aligned with the dest; go fast.
src_strategy_blend(span, fNext, &fAccessor);
} else {
// There is some sub-pixel offsets, so bilerp.
this->spanUnitRate(span);
}
} else if (absLength < 2.0f * (count - 1)) {
// 1 < |dx| < 2.
this->spanMediumRate(span);
} else {
// |dx| >= 2.
this->spanFastRate(span);
}
}
void repeatSpan(Span span, int32_t repeatCount) override {
while (repeatCount > 0) {
this->pointSpan(span);
repeatCount--;
}
}
private:
// Convert a sample point to the points used by the filter.
void filterPoints(SkPoint sample, Sk4i* filterXs, Sk4i* filterYs) {
// May be less than zero. Be careful to use Floor.
int x0 = adjust_edge(fXEdgeType, SkScalarFloorToInt(X(sample) - 0.5), fXMax);
// Always greater than zero. Use the faster Trunc.
int x1 = adjust_edge(fXEdgeType, SkScalarTruncToInt(X(sample) + 0.5), fXMax);
int y0 = adjust_edge(fYEdgeType, SkScalarFloorToInt(Y(sample) - 0.5), fYMax);
int y1 = adjust_edge(fYEdgeType, SkScalarTruncToInt(Y(sample) + 0.5), fYMax);
*filterXs = Sk4i{x0, x1, x0, x1};
*filterYs = Sk4i{y0, y0, y1, y1};
}
// Given a sample point, generate a color by bilerping the four filter points.
Sk4f bilerpSamplePoint(SkPoint sample) {
Sk4i iXs, iYs;
filterPoints(sample, &iXs, &iYs);
Sk4f px00, px10, px01, px11;
fAccessor.get4Pixels(iXs, iYs, &px00, &px10, &px01, &px11);
return bilerp4(Sk4f{X(sample) - 0.5f}, Sk4f{Y(sample) - 0.5f}, px00, px10, px01, px11);
}
// Get two pixels at x from row0 and row1.
void get2PixelColumn(const void* row0, const void* row1, int x, Sk4f* px0, Sk4f* px1) {
*px0 = fAccessor.getPixelFromRow(row0, x);
*px1 = fAccessor.getPixelFromRow(row1, x);
}
// |dx| == 0. This code assumes that length is zero.
void spanZeroRate(Span span) {
SkPoint start; SkScalar length; int count;
std::tie(start, length, count) = span;
SkASSERT(length == 0.0f);
// Filter for the blending of the top and bottom pixels.
SkScalar filterY = sample_to_filter(Y(start));
// Generate the four filter points from the sample point start. Generate the row* values.
Sk4i iXs, iYs;
this->filterPoints(start, &iXs, &iYs);
const void* const row0 = fAccessor.row(iYs[0]);
const void* const row1 = fAccessor.row(iYs[2]);
// Get the two pixels that make up the clamping pixel.
Sk4f pxTop, pxBottom;
this->get2PixelColumn(row0, row1, SkScalarFloorToInt(X(start)), &pxTop, &pxBottom);
Sk4f pixel = pxTop * filterY + (1.0f - filterY) * pxBottom;
while (count >= 4) {
fNext->blend4Pixels(pixel, pixel, pixel, pixel);
count -= 4;
}
while (count > 0) {
fNext->blendPixel(pixel);
count -= 1;
}
}
// 0 < |dx| < 1. This code reuses the calculations from previous pixels to reduce
// computation. In particular, several destination pixels maybe generated from the same four
// source pixels.
// In the following code a "part" is a combination of two pixels from the same column of the
// filter.
void spanSlowRate(Span span) {
SkPoint start; SkScalar length; int count;
std::tie(start, length, count) = span;
// Calculate the distance between each sample point.
const SkScalar dx = length / (count - 1);
SkASSERT(-1.0f < dx && dx < 1.0f && dx != 0.0f);
// Generate the filter values for the top-left corner.
// Note: these values are in filter space; this has implications about how to adjust
// these values at each step. For example, as the sample point increases, the filter
// value decreases, this is because the filter and position are related by
// (1 - (X(sample) - .5)) % 1. The (1 - stuff) causes the filter to move in the opposite
// direction of the sample point which is increasing by dx.
SkScalar filterX = sample_to_filter(X(start));
SkScalar filterY = sample_to_filter(Y(start));
// Generate the four filter points from the sample point start. Generate the row* values.
Sk4i iXs, iYs;
this->filterPoints(start, &iXs, &iYs);
const void* const row0 = fAccessor.row(iYs[0]);
const void* const row1 = fAccessor.row(iYs[2]);
// Generate part of the filter value at xColumn.
auto partAtColumn = [&](int xColumn) {
int adjustedColumn = adjust_edge(fXEdgeType, xColumn, fXMax);
Sk4f pxTop, pxBottom;
this->get2PixelColumn(row0, row1, adjustedColumn, &pxTop, &pxBottom);
return pxTop * filterY + (1.0f - filterY) * pxBottom;
};
// The leftPart is made up of two pixels from the left column of the filter, right part
// is similar. The top and bottom pixels in the *Part are created as a linear blend of
// the top and bottom pixels using filterY. See the partAtColumn function above.
Sk4f leftPart = partAtColumn(iXs[0]);
Sk4f rightPart = partAtColumn(iXs[1]);
// Create a destination color by blending together a left and right part using filterX.
auto bilerp = [&](const Sk4f& leftPart, const Sk4f& rightPart) {
Sk4f pixel = leftPart * filterX + rightPart * (1.0f - filterX);
return check_pixel(pixel);
};
// Send the first pixel to the destination. This simplifies the loop structure so that no
// extra pixels are fetched for the last iteration of the loop.
fNext->blendPixel(bilerp(leftPart, rightPart));
count -= 1;
if (dx > 0.0f) {
// * positive direction - generate destination pixels by sliding the filter from left
// to right.
int rightPartCursor = iXs[1];
// Advance the filter from left to right. Remember that moving the top-left corner of
// the filter to the right actually makes the filter value smaller.
auto advanceFilter = [&]() {
filterX -= dx;
if (filterX <= 0.0f) {
filterX += 1.0f;
leftPart = rightPart;
rightPartCursor += 1;
rightPart = partAtColumn(rightPartCursor);
}
SkASSERT(0.0f < filterX && filterX <= 1.0f);
return bilerp(leftPart, rightPart);
};
while (count >= 4) {
Sk4f px0 = advanceFilter(),
px1 = advanceFilter(),
px2 = advanceFilter(),
px3 = advanceFilter();
fNext->blend4Pixels(px0, px1, px2, px3);
count -= 4;
}
while (count > 0) {
fNext->blendPixel(advanceFilter());
count -= 1;
}
} else {
// * negative direction - generate destination pixels by sliding the filter from
// right to left.
int leftPartCursor = iXs[0];
// Advance the filter from right to left. Remember that moving the top-left corner of
// the filter to the left actually makes the filter value larger.
auto advanceFilter = [&]() {
// Remember, dx < 0 therefore this adds |dx| to filterX.
filterX -= dx;
// At this point filterX may be > 1, and needs to be wrapped back on to the filter
// interval, and the next column in the filter is calculated.
if (filterX > 1.0f) {
filterX -= 1.0f;
rightPart = leftPart;
leftPartCursor -= 1;
leftPart = partAtColumn(leftPartCursor);
}
SkASSERT(0.0f < filterX && filterX <= 1.0f);
return bilerp(leftPart, rightPart);
};
while (count >= 4) {
Sk4f px0 = advanceFilter(),
px1 = advanceFilter(),
px2 = advanceFilter(),
px3 = advanceFilter();
fNext->blend4Pixels(px0, px1, px2, px3);
count -= 4;
}
while (count > 0) {
fNext->blendPixel(advanceFilter());
count -= 1;
}
}
}
// |dx| == 1. Moving through source space at a rate of 1 source pixel per 1 dst pixel.
// Every filter part is used for two destination pixels, and the code can bulk load four
// pixels at a time.
void spanUnitRate(Span span) {
SkPoint start; SkScalar length; int count;
std::tie(start, length, count) = span;
SkASSERT(SkScalarAbs(length) == (count - 1));
// Calculate the four filter points of start, and use the two different Y values to
// generate the row pointers.
Sk4i iXs, iYs;
filterPoints(start, &iXs, &iYs);
const void* row0 = fAccessor.row(iYs[0]);
const void* row1 = fAccessor.row(iYs[2]);
// Calculate the filter values for the top-left filter element.
const SkScalar filterX = sample_to_filter(X(start));
const SkScalar filterY = sample_to_filter(Y(start));
// Generate part of the filter value at xColumn.
auto partAtColumn = [&](int xColumn) {
int adjustedColumn = adjust_edge(fXEdgeType, xColumn, fXMax);
Sk4f pxTop, pxBottom;
this->get2PixelColumn(row0, row1, adjustedColumn, &pxTop, &pxBottom);
return pxTop * filterY + (1.0f - filterY) * pxBottom;
};
auto get4Parts = [&](int ix, Sk4f* part0, Sk4f* part1, Sk4f* part2, Sk4f* part3) {
// Check if the pixels needed are near the edges. If not go fast using bulk pixels,
// otherwise be careful.
if (0 <= ix && ix <= fXMax - 3) {
Sk4f px00, px10, px20, px30,
px01, px11, px21, px31;
fAccessor.get4Pixels(row0, ix, &px00, &px10, &px20, &px30);
fAccessor.get4Pixels(row1, ix, &px01, &px11, &px21, &px31);
*part0 = filterY * px00 + (1.0f - filterY) * px01;
*part1 = filterY * px10 + (1.0f - filterY) * px11;
*part2 = filterY * px20 + (1.0f - filterY) * px21;
*part3 = filterY * px30 + (1.0f - filterY) * px31;
} else {
*part0 = partAtColumn(ix + 0);
*part1 = partAtColumn(ix + 1);
*part2 = partAtColumn(ix + 2);
*part3 = partAtColumn(ix + 3);
}
};
auto bilerp = [&](const Sk4f& part0, const Sk4f& part1) {
return part0 * filterX + part1 * (1.0f - filterX);
};
if (length > 0) {
// * positive direction - generate destination pixels by sliding the filter from left
// to right.
// overlapPart is the filter part from the end of the previous four pixels used at
// the start of the next four pixels.
Sk4f overlapPart = partAtColumn(iXs[0]);
int rightColumnCursor = iXs[1];
while (count >= 4) {
Sk4f part0, part1, part2, part3;
get4Parts(rightColumnCursor, &part0, &part1, &part2, &part3);
Sk4f px0 = bilerp(overlapPart, part0);
Sk4f px1 = bilerp(part0, part1);
Sk4f px2 = bilerp(part1, part2);
Sk4f px3 = bilerp(part2, part3);
overlapPart = part3;
fNext->blend4Pixels(px0, px1, px2, px3);
rightColumnCursor += 4;
count -= 4;
}
while (count > 0) {
Sk4f rightPart = partAtColumn(rightColumnCursor);
fNext->blendPixel(bilerp(overlapPart, rightPart));
overlapPart = rightPart;
rightColumnCursor += 1;
count -= 1;
}
} else {
// * negative direction - generate destination pixels by sliding the filter from
// right to left.
Sk4f overlapPart = partAtColumn(iXs[1]);
int leftColumnCursor = iXs[0];
while (count >= 4) {
Sk4f part0, part1, part2, part3;
get4Parts(leftColumnCursor - 3, &part3, &part2, &part1, &part0);
Sk4f px0 = bilerp(part0, overlapPart);
Sk4f px1 = bilerp(part1, part0);
Sk4f px2 = bilerp(part2, part1);
Sk4f px3 = bilerp(part3, part2);
overlapPart = part3;
fNext->blend4Pixels(px0, px1, px2, px3);
leftColumnCursor -= 4;
count -= 4;
}
while (count > 0) {
Sk4f leftPart = partAtColumn(leftColumnCursor);
fNext->blendPixel(bilerp(leftPart, overlapPart));
overlapPart = leftPart;
leftColumnCursor -= 1;
count -= 1;
}
}
}
// 1 < |dx| < 2. Going through the source pixels at a faster rate than the dest pixels, but
// still slow enough to take advantage of previous calculations.
void spanMediumRate(Span span) {
SkPoint start; SkScalar length; int count;
std::tie(start, length, count) = span;
// Calculate the distance between each sample point.
const SkScalar dx = length / (count - 1);
SkASSERT((-2.0f < dx && dx < -1.0f) || (1.0f < dx && dx < 2.0f));
// Generate the filter values for the top-left corner.
// Note: these values are in filter space; this has implications about how to adjust
// these values at each step. For example, as the sample point increases, the filter
// value decreases, this is because the filter and position are related by
// (1 - (X(sample) - .5)) % 1. The (1 - stuff) causes the filter to move in the opposite
// direction of the sample point which is increasing by dx.
SkScalar filterX = sample_to_filter(X(start));
SkScalar filterY = sample_to_filter(Y(start));
// Generate the four filter points from the sample point start. Generate the row* values.
Sk4i iXs, iYs;
this->filterPoints(start, &iXs, &iYs);
const void* const row0 = fAccessor.row(iYs[0]);
const void* const row1 = fAccessor.row(iYs[2]);
// Generate part of the filter value at xColumn.
auto partAtColumn = [&](int xColumn) {
int adjustedColumn = adjust_edge(fXEdgeType, xColumn, fXMax);
Sk4f pxTop, pxBottom;
this->get2PixelColumn(row0, row1, adjustedColumn, &pxTop, &pxBottom);
return pxTop * filterY + (1.0f - filterY) * pxBottom;
};
// The leftPart is made up of two pixels from the left column of the filter, right part
// is similar. The top and bottom pixels in the *Part are created as a linear blend of
// the top and bottom pixels using filterY. See the nextPart function below.
Sk4f leftPart = partAtColumn(iXs[0]);
Sk4f rightPart = partAtColumn(iXs[1]);
// Create a destination color by blending together a left and right part using filterX.
auto bilerp = [&](const Sk4f& leftPart, const Sk4f& rightPart) {
Sk4f pixel = leftPart * filterX + rightPart * (1.0f - filterX);
return check_pixel(pixel);
};
// Send the first pixel to the destination. This simplifies the loop structure so that no
// extra pixels are fetched for the last iteration of the loop.
fNext->blendPixel(bilerp(leftPart, rightPart));
count -= 1;
if (dx > 0.0f) {
// * positive direction - generate destination pixels by sliding the filter from left
// to right.
int rightPartCursor = iXs[1];
// Advance the filter from left to right. Remember that moving the top-left corner of
// the filter to the right actually makes the filter value smaller.
auto advanceFilter = [&]() {
filterX -= dx;
// At this point filterX is less than zero, but might actually be less than -1.
if (filterX > -1.0f) {
filterX += 1.0f;
leftPart = rightPart;
rightPartCursor += 1;
rightPart = partAtColumn(rightPartCursor);
} else {
filterX += 2.0f;
rightPartCursor += 2;
leftPart = partAtColumn(rightPartCursor - 1);
rightPart = partAtColumn(rightPartCursor);
}
SkASSERT(0.0f < filterX && filterX <= 1.0f);
return bilerp(leftPart, rightPart);
};
while (count >= 4) {
Sk4f px0 = advanceFilter(),
px1 = advanceFilter(),
px2 = advanceFilter(),
px3 = advanceFilter();
fNext->blend4Pixels(px0, px1, px2, px3);
count -= 4;
}
while (count > 0) {
fNext->blendPixel(advanceFilter());
count -= 1;
}
} else {
// * negative direction - generate destination pixels by sliding the filter from
// right to left.
int leftPartCursor = iXs[0];
auto advanceFilter = [&]() {
// Remember, dx < 0 therefore this adds |dx| to filterX.
filterX -= dx;
// At this point, filterX is greater than one, but may actually be greater than two.
if (filterX < 2.0f) {
filterX -= 1.0f;
rightPart = leftPart;
leftPartCursor -= 1;
leftPart = partAtColumn(leftPartCursor);
} else {
filterX -= 2.0f;
leftPartCursor -= 2;
rightPart = partAtColumn(leftPartCursor - 1);
leftPart = partAtColumn(leftPartCursor);
}
SkASSERT(0.0f < filterX && filterX <= 1.0f);
return bilerp(leftPart, rightPart);
};
while (count >= 4) {
Sk4f px0 = advanceFilter(),
px1 = advanceFilter(),
px2 = advanceFilter(),
px3 = advanceFilter();
fNext->blend4Pixels(px0, px1, px2, px3);
count -= 4;
}
while (count > 0) {
fNext->blendPixel(advanceFilter());
count -= 1;
}
}
}
// We're moving through source space faster than dst (zoomed out),
// so we'll never reuse a source pixel or be able to do contiguous loads.
void spanFastRate(Span span) {
SkPoint start; SkScalar length; int count;
std::tie(start, length, count) = span;
SkScalar x = X(start);
SkScalar y = Y(start);
SkScalar dx = length / (count - 1);
while (count > 0) {
fNext->blendPixel(this->bilerpSamplePoint(SkPoint{x, y}));
x += dx;
count -= 1;
}
}
Next* const fNext;
const SkShader::TileMode fXEdgeType;
const int fXMax;
const SkShader::TileMode fYEdgeType;
const int fYMax;
Accessor fAccessor;
};
} // namespace
#endif // SkLinearBitmapPipeline_sampler_DEFINED