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/*
* 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_core_DEFINED
#define SkLinearBitmapPipeline_core_DEFINED
#include <cmath>
#include "SkNx.h"
// New bilerp strategy:
// Pass through on bilerpList4 and bilerpListFew (analogs to pointList), introduce bilerpEdge
// which takes 4 points. If the sample spans an edge, then break it into a bilerpEdge. Bilerp
// span then becomes a normal span except in special cases where an extra Y is given. The bilerp
// need to stay single point calculations until the tile layer.
// TODO:
// - edge span predicate.
// - introduce new point API
// - Add tile for new api.
// Tweak ABI of functions that pass Sk4f by value to pass them via registers.
#if defined(_MSC_VER) && SK_CPU_SSE_LEVEL >= SK_CPU_SSE_LEVEL_SSE2
#define VECTORCALL __vectorcall
#elif defined(SK_CPU_ARM32) && defined(SK_ARM_HAS_NEON)
#define VECTORCALL __attribute__((pcs("aapcs-vfp")))
#else
#define VECTORCALL
#endif
namespace {
struct X {
explicit X(SkScalar val) : fVal{val} { }
explicit X(SkPoint pt) : fVal{pt.fX} { }
explicit X(SkSize s) : fVal{s.fWidth} { }
explicit X(SkISize s) : fVal((SkScalar)s.fWidth) { }
operator SkScalar () const {return fVal;}
private:
SkScalar fVal;
};
struct Y {
explicit Y(SkScalar val) : fVal{val} { }
explicit Y(SkPoint pt) : fVal{pt.fY} { }
explicit Y(SkSize s) : fVal{s.fHeight} { }
explicit Y(SkISize s) : fVal((SkScalar)s.fHeight) { }
operator SkScalar () const {return fVal;}
private:
SkScalar fVal;
};
// The Span class enables efficient processing horizontal spans of pixels.
// * start - the point where to start the span.
// * length - the number of pixels to traverse in source space.
// * count - the number of pixels to produce in destination space.
// Both start and length are mapped through the inversion matrix to produce values in source
// space. After the matrix operation, the tilers may break the spans up into smaller spans.
// The tilers can produce spans that seem nonsensical.
// * The clamp tiler can create spans with length of 0. This indicates to copy an edge pixel out
// to the edge of the destination scan.
// * The mirror tiler can produce spans with negative length. This indicates that the source
// should be traversed in the opposite direction to the destination pixels.
class Span {
public:
Span(SkPoint start, SkScalar length, int count)
: fStart(start)
, fLength(length)
, fCount{count} {
SkASSERT(std::isfinite(length));
}
operator std::tuple<SkPoint&, SkScalar&, int&>() {
return std::tie(fStart, fLength, fCount);
}
bool isEmpty() const { return 0 == fCount; }
void clear() { fCount = 0; }
int count() const { return fCount; }
SkScalar length() const { return fLength; }
SkScalar startX() const { return X(fStart); }
SkScalar endX() const { return this->startX() + this->length(); }
SkScalar startY() const { return Y(fStart); }
Span emptySpan() { return Span{{0.0, 0.0}, 0.0f, 0}; }
bool completelyWithin(SkScalar xMin, SkScalar xMax) const {
SkScalar sMin, sMax;
std::tie(sMin, sMax) = std::minmax(startX(), endX());
return xMin <= sMin && sMax < xMax;
}
void offset(SkScalar offsetX) {
fStart.offset(offsetX, 0.0f);
}
Span breakAt(SkScalar breakX, SkScalar dx) {
SkASSERT(std::isfinite(breakX));
SkASSERT(std::isfinite(dx));
SkASSERT(dx != 0.0f);
if (this->isEmpty()) {
return this->emptySpan();
}
int dxSteps = SkScalarFloorToInt((breakX - this->startX()) / dx);
if (dxSteps < 0) {
// The span is wholly after breakX.
return this->emptySpan();
} else if (dxSteps >= fCount) {
// The span is wholly before breakX.
Span answer = *this;
this->clear();
return answer;
}
// Calculate the values for the span to cleave off.
SkScalar newLength = dxSteps * dx;
// If the last (or first if count = 1) sample lands directly on the boundary. Include it
// when dx < 0 and exclude it when dx > 0.
// Reasoning:
// dx > 0: The sample point on the boundary is part of the next span because the entire
// pixel is after the boundary.
// dx < 0: The sample point on the boundary is part of the current span because the
// entire pixel is before the boundary.
if (this->startX() + newLength == breakX && dx > 0) {
if (dxSteps > 0) {
dxSteps -= 1;
newLength -= dx;
} else {
return this->emptySpan();
}
}
// Calculate new span parameters
SkPoint newStart = fStart;
int newCount = dxSteps + 1;
SkASSERT(newCount > 0);
// Update this span to reflect the break.
SkScalar lengthToStart = newLength + dx;
fLength -= lengthToStart;
fCount -= newCount;
fStart = {this->startX() + lengthToStart, Y(fStart)};
return Span{newStart, newLength, newCount};
}
void clampToSinglePixel(SkPoint pixel) {
fStart = pixel;
fLength = 0.0f;
}
private:
SkPoint fStart;
SkScalar fLength;
int fCount;
};
template<typename Stage>
void span_fallback(Span span, Stage* stage) {
SkPoint start;
SkScalar length;
int count;
std::tie(start, length, count) = span;
Sk4f xs{X(start)};
Sk4f ys{Y(start)};
// Initializing this is not needed, but some compilers can't figure this out.
Sk4s fourDx{0.0f};
if (count > 1) {
SkScalar dx = length / (count - 1);
xs = xs + Sk4f{0.0f, 1.0f, 2.0f, 3.0f} * dx;
// Only used if count is >= 4.
fourDx = Sk4f{4.0f * dx};
}
while (count >= 4) {
stage->pointList4(xs, ys);
xs = xs + fourDx;
count -= 4;
}
if (count > 0) {
stage->pointListFew(count, xs, ys);
}
}
} // namespace
#endif // SkLinearBitmapPipeline_core_DEFINED
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