if (dstIdx < srcIdx) { // The destination pixels are not effected by the src pixels, // change to zero as per the spec. // https://drafts.fxtf.org/filter-effects/#FilterPrimitivesOverviewIntro int commonEnd = std::min(srcIdx, dstEnd); while (dstIdx < commonEnd) {
*dstCursor = 0;
dstCursor += dstStride;
SK_PREFETCH(dstCursor);
dstIdx++;
}
} elseif (srcIdx < dstIdx) { // The edge of the source is before the edge of the destination. Calculate the sums for // the pixels before the start of the destination. if (int commonEnd = std::min(dstIdx, srcEnd); srcIdx < commonEnd) { // Preload the blur with values from src before dst is entered. int n = commonEnd - srcIdx;
this->blurSegment(n, srcCursor, srcStride, nullptr, 0);
srcIdx += n;
srcCursor += n * srcStride;
} if (srcIdx < dstIdx) { // The weird case where src is out of pixels before dst is even started. int n = dstIdx - srcIdx;
this->blurSegment(n, nullptr, 0, nullptr, 0);
srcIdx += n;
}
}
if (int commonEnd = std::min(dstEnd, srcEnd); dstIdx < commonEnd) { // Both srcIdx and dstIdx are in sync now, and can run in a 1:1 fashion. This is the // normal mode of operation.
SkASSERT(srcIdx == dstIdx);
int n = commonEnd - dstIdx;
this->blurSegment(n, srcCursor, srcStride, dstCursor, dstStride);
srcCursor += n * srcStride;
dstCursor += n * dstStride;
dstIdx += n;
srcIdx += n;
}
// Drain the remaining blur values into dst assuming 0's for the leading edge. if (dstIdx < dstEnd) { int n = dstEnd - dstIdx;
this->blurSegment(n, nullptr, 0, dstCursor, dstStride);
}
}
protected: virtualvoid startBlur() = 0; virtualvoid blurSegment( int n, const uint32_t* src, int srcStride, uint32_t* dst, int dstStride) = 0;
// Implement a scanline processor that uses a three-box filter to approximate a Gaussian blur. // The GaussPass is limit to processing sigmas < 135. class GaussPass final : public Pass { public: // NB 136 is the largest sigma that will not cause a buffer full of 255 mask values to overflow // using the Gauss filter. It also limits the size of buffers used hold intermediate values. // Explanation of maximums: // sum0 = window * 255 // sum1 = window * sum0 -> window * window * 255 // sum2 = window * sum1 -> window * window * window * 255 -> window^3 * 255 // // The value window^3 * 255 must fit in a uint32_t. So, // window^3 < 2^32. window = 255. // // window = floor(sigma * 3 * sqrt(2 * kPi) / 4 + 0.5) // For window <= 255, the largest value for sigma is 136. static PassMaker* MakeMaker(float sigma, SkArenaAlloc* alloc) {
SkASSERT(0 <= sigma); int window = SkBlurEngine::BoxBlurWindow(sigma); if (255 <= window) { return nullptr;
}
size_t bufferSizeBytes() const override { int window = this->window();
size_t onePassSize = window - 1; // If the window is odd, then there is an obvious middle element. For even sizes // 2 passes are shifted, and the last pass has an extra element. Like this: // S // aaaAaa // bbBbbb // cccCccc // D
size_t bufferCount = (window & 1) == 1 ? 3 * onePassSize : 3 * onePassSize + 1; return bufferCount * sizeof(skvx::Vec<4, uint32_t>);
}
};
return alloc->make<Maker>(window);
}
static GaussPass* Make(int window, void* buffers, SkArenaAlloc* alloc) { // We don't need to store the trailing edge pixel in the buffer; int passSize = window - 1;
skvx::Vec<4, uint32_t>* buffer0 = static_cast<skvx::Vec<4, uint32_t>*>(buffers);
skvx::Vec<4, uint32_t>* buffer1 = buffer0 + passSize;
skvx::Vec<4, uint32_t>* buffer2 = buffer1 + passSize; // If the window is odd just one buffer is needed, but if it's even, then there is one // more element on that pass.
skvx::Vec<4, uint32_t>* buffersEnd = buffer2 + ((window & 1) ? passSize : passSize + 1);
// Calculating the border is tricky. The border is the distance in pixels between the first // dst pixel and the first src pixel (or the last src pixel and the last dst pixel). // I will go through the odd case which is simpler, and then through the even case. Given a // stack of filters seven wide for the odd case of three passes. // // S // aaaAaaa // bbbBbbb // cccCccc // D // // The furthest changed pixel is when the filters are in the following configuration. // // S // aaaAaaa // bbbBbbb // cccCccc // D // // The A pixel is calculated using the value S, the B uses A, and the C uses B, and // finally D is C. So, with a window size of seven the border is nine. In the odd case, the // border is 3*((window - 1)/2). // // For even cases the filter stack is more complicated. The spec specifies two passes // of even filters and a final pass of odd filters. A stack for a width of six looks like // this. // // S // aaaAaa // bbBbbb // cccCccc // D // // The furthest pixel looks like this. // // S // aaaAaa // bbBbbb // cccCccc // D // // For a window of six, the border value is eight. In the even case the border is 3 * // (window/2) - 1. int border = (window & 1) == 1 ? 3 * ((window - 1) / 2) : 3 * (window / 2) - 1;
// If the window is odd then the divisor is just window ^ 3 otherwise, // it is window * window * (window + 1) = window ^ 3 + window ^ 2; int window2 = window * window; int window3 = window2 * window; int divisor = (window & 1) == 1 ? window3 : window3 + window2; return alloc->make<GaussPass>(buffer0, buffer1, buffer2, buffersEnd, border, divisor);
}
// GaussPass implements the common three pass box filter approximation of Gaussian blur, // but combines all three passes into a single pass. This approach is facilitated by three // circular buffers the width of the window which track values for trailing edges of each of // the three passes. This allows the algorithm to use more precision in the calculation // because the values are not rounded each pass. And this implementation also avoids a trap // that's easy to fall into resulting in blending in too many zeroes near the edge. // // In general, a window sum has the form: // sum_n+1 = sum_n + leading_edge - trailing_edge. // If instead we do the subtraction at the end of the previous iteration, we can just // calculate the sums instead of having to do the subtractions too. // // In previous iteration: // sum_n+1 = sum_n - trailing_edge. // // In this iteration: // sum_n+1 = sum_n + leading_edge. // // Now we can stack all three sums and do them at once. Sum0 gets its leading edge from the // actual data. Sum1's leading edge is just Sum0, and Sum2's leading edge is Sum1. So, doing the // three passes at the same time has the form: // // sum0_n+1 = sum0_n + leading edge // sum1_n+1 = sum1_n + sum0_n+1 // sum2_n+1 = sum2_n + sum1_n+1 // // sum2_n+1 / window^3 is the new value of the destination pixel. // // Reduce the sums by the trailing edges which were stored in the circular buffers for the // next go around. This is the case for odd sized windows, even windows the the third // circular buffer is one larger then the first two circular buffers. // // sum2_n+2 = sum2_n+1 - buffer2[i]; // buffer2[i] = sum1; // sum1_n+2 = sum1_n+1 - buffer1[i]; // buffer1[i] = sum0; // sum0_n+2 = sum0_n+1 - buffer0[i]; // buffer0[i] = leading edge void blurSegment( int n, const uint32_t* src, int srcStride, uint32_t* dst, int dstStride) override { #if SK_CPU_LSX_LEVEL >= SK_CPU_LSX_LEVEL_LSX
skvx::Vec<4, uint32_t>* buffer0Cursor = fBuffer0Cursor;
skvx::Vec<4, uint32_t>* buffer1Cursor = fBuffer1Cursor;
skvx::Vec<4, uint32_t>* buffer2Cursor = fBuffer2Cursor;
v4u32 sum0 = __lsx_vld(fSum0, 0); // same as skvx::Vec<4, uint32_t>::Load(fSum0);
v4u32 sum1 = __lsx_vld(fSum1, 0);
v4u32 sum2 = __lsx_vld(fSum2, 0);
// Implement a scanline processor that uses a two-box filter to approximate a Tent filter. // The TentPass is limit to processing sigmas < 2183. class TentPass final : public Pass { public: // NB 2183 is the largest sigma that will not cause a buffer full of 255 mask values to overflow // using the Tent filter. It also limits the size of buffers used hold intermediate values. // Explanation of maximums: // sum0 = window * 255 // sum1 = window * sum0 -> window * window * 255 // // The value window^2 * 255 must fit in a uint32_t. So, // window^2 < 2^32. window = 4104. // // window = floor(sigma * 3 * sqrt(2 * kPi) / 4 + 0.5) // For window <= 4104, the largest value for sigma is 2183. static PassMaker* MakeMaker(float sigma, SkArenaAlloc* alloc) {
SkASSERT(0 <= sigma); int gaussianWindow = SkBlurEngine::BoxBlurWindow(sigma); // This is a naive method of using the window size for the Gaussian blur to calculate the // window size for the Tent blur. This seems to work well in practice. // // We can use a single pixel to generate the effective blur area given a window size. For // the Gaussian blur this is 3 * window size. For the Tent filter this is 2 * window size. int tentWindow = 3 * gaussianWindow / 2; if (tentWindow >= 4104) { return nullptr;
}
size_t bufferSizeBytes() const override {
size_t onePassSize = this->window() - 1; // If the window is odd, then there is an obvious middle element. For even sizes 2 // passes are shifted, and the last pass has an extra element. Like this: // S // aaaAaa // bbBbbb // D
size_t bufferCount = 2 * onePassSize; return bufferCount * sizeof(skvx::Vec<4, uint32_t>);
}
};
// We don't need to store the trailing edge pixel in the buffer; int passSize = window - 1;
skvx::Vec<4, uint32_t>* buffer0 = static_cast<skvx::Vec<4, uint32_t>*>(buffers);
skvx::Vec<4, uint32_t>* buffer1 = buffer0 + passSize;
skvx::Vec<4, uint32_t>* buffersEnd = buffer1 + passSize;
// Calculating the border is tricky. The border is the distance in pixels between the first // dst pixel and the first src pixel (or the last src pixel and the last dst pixel). // I will go through the odd case which is simpler, and then through the even case. Given a // stack of filters seven wide for the odd case of three passes. // // S // aaaAaaa // bbbBbbb // D // // The furthest changed pixel is when the filters are in the following configuration. // // S // aaaAaaa // bbbBbbb // D // // The A pixel is calculated using the value S, the B uses A, and the D uses B. // So, with a window size of seven the border is nine. In the odd case, the border is // window - 1. // // For even cases the filter stack is more complicated. It uses two passes // of even filters offset from each other. A stack for a width of six looks like // this. // // S // aaaAaa // bbBbbb // D // // The furthest pixel looks like this. // // S // aaaAaa // bbBbbb // D // // For a window of six, the border value is 5. In the even case the border is // window - 1. int border = window - 1;
// TentPass implements the common two pass box filter approximation of Tent filter, // but combines all both passes into a single pass. This approach is facilitated by two // circular buffers the width of the window which track values for trailing edges of each of // both passes. This allows the algorithm to use more precision in the calculation // because the values are not rounded each pass. And this implementation also avoids a trap // that's easy to fall into resulting in blending in too many zeroes near the edge. // // In general, a window sum has the form: // sum_n+1 = sum_n + leading_edge - trailing_edge. // If instead we do the subtraction at the end of the previous iteration, we can just // calculate the sums instead of having to do the subtractions too. // // In previous iteration: // sum_n+1 = sum_n - trailing_edge. // // In this iteration: // sum_n+1 = sum_n + leading_edge. // // Now we can stack all three sums and do them at once. Sum0 gets its leading edge from the // actual data. Sum1's leading edge is just Sum0, and Sum2's leading edge is Sum1. So, doing the // three passes at the same time has the form: // // sum0_n+1 = sum0_n + leading edge // sum1_n+1 = sum1_n + sum0_n+1 // // sum1_n+1 / window^2 is the new value of the destination pixel. // // Reduce the sums by the trailing edges which were stored in the circular buffers for the // next go around. // // sum1_n+2 = sum1_n+1 - buffer1[i]; // buffer1[i] = sum0; // sum0_n+2 = sum0_n+1 - buffer0[i]; // buffer0[i] = leading edge void blurSegment( int n, const uint32_t* src, int srcStride, uint32_t* dst, int dstStride) override {
skvx::Vec<4, uint32_t>* buffer0Cursor = fBuffer0Cursor;
skvx::Vec<4, uint32_t>* buffer1Cursor = fBuffer1Cursor;
skvx::Vec<4, uint32_t> sum0 = skvx::Vec<4, uint32_t>::Load(fSum0);
skvx::Vec<4, uint32_t> sum1 = skvx::Vec<4, uint32_t>::Load(fSum1);
// Given an expanded input pixel, move the window ahead using the leadingEdge value. auto processValue = [&](const skvx::Vec<4, uint32_t>& leadingEdge) {
sum0 += leadingEdge;
sum1 += sum0;
class Raster8888BlurAlgorithm : public SkBlurEngine::Algorithm { public: // See analysis in description of TentPass for the max supported sigma. float maxSigma() const override { // TentPass supports a sigma up to 2183, and was added so that the CPU blur algorithm's // blur radius was as large as that supported by the GPU. GaussPass only supports up to 136. // However, there is a very apparent pop in blur weight when switching from successive box // blurs to the tent filter. The TentPass is preserved for legacy blurs, which do not use // FilterResult::rescale(). However, using kMaxSigma = 135 with the raster SkBlurEngine // ensures that the non-legacy raster blurs will always use the GaussPass implementation. // This is about 6-7x faster on large blurs to rescale a few times to a lower resolution // than it is to evaluate the much larger original window. static constexpr float kMaxSigma = 135.f;
SkASSERT(SkBlurEngine::BoxBlurWindow(kMaxSigma) <= 255); // see GaussPass::MakeMaker(). return kMaxSigma;
}
// TODO: Implement CPU backend for different fTileMode. This is still worth doing inline with // the blur; at the moment the tiling is applied via the CropImageFilter and carried as metadata // on the FilterResult. This is forcefully applied in FilterResult::Builder::blur() when // supportsOnlyDecalTiling() returns true. bool supportsOnlyDecalTiling() const override { returntrue; }
sk_sp<SkSpecialImage> blur(SkSize sigma,
sk_sp<SkSpecialImage> input, const SkIRect& originalSrcBounds,
SkTileMode tileMode, const SkIRect& originalDstBounds) const override { // TODO: Enable this assert when the TentPass is no longer used for legacy blurs // (which supports blur sigmas larger than what's reported in maxSigma()). // SkASSERT(sigma.width() <= this->maxSigma() && sigma.height() <= this->maxSigma());
SkASSERT(tileMode == SkTileMode::kDecal);
SkBitmap src; if (!SkSpecialImages::AsBitmap(input.get(), &src)) { return nullptr; // Should only have been called by CPU-backed images
} // The blur engine should not have picked this algorithm for a non-32-bit color type
SkASSERT(src.colorType() == kRGBA_8888_SkColorType ||
src.colorType() == kBGRA_8888_SkColorType);
SkSTArenaAlloc<1024> alloc; auto makeMaker = [&](float sigma) -> PassMaker* {
SkASSERT(0 <= sigma && sigma <= 2183); // should be guaranteed after map_sigma if (PassMaker* maker = GaussPass::MakeMaker(sigma, &alloc)) { return maker;
} if (PassMaker* maker = TentPass::MakeMaker(sigma, &alloc)) { return maker;
}
SK_ABORT("Sigma is out of range.");
};
PassMaker* makerX = makeMaker(sigma.width());
PassMaker* makerY = makeMaker(sigma.height()); // A blur with a sigma smaller than the successive box-blurs accuracy should have been // routed to the shader-based algorithm.
SkASSERT(makerX->window() > 1 || makerY->window() > 1);
SkIRect srcBounds = originalSrcBounds;
SkIRect dstBounds = originalDstBounds; if (makerX->window() > 1) { // Inflate the dst by the window required for the Y pass so that the X pass can prepare // it. The Y pass will be offset to only write to the original rows in dstBounds, but // its window will access these extra rows calculated by the X pass. The SpecialImage // factory will then subset the bitmap so it appears to match 'originalDstBounds' // tightly. We make one slightly larger image to hold this extra data instead of two // separate images sized exactly to each pass because the CPU blur can write in place.
dstBounds.outset(0, SkBlurEngine::SigmaToRadius(sigma.height()));
}
auto buffer = alloc.makeBytesAlignedTo(std::max(makerX->bufferSizeBytes(),
makerY->bufferSizeBytes()),
alignof(skvx::Vec<4, uint32_t>));
// Basic Plan: The three cases to handle // * Horizontal and Vertical - blur horizontally while copying values from the source to // the destination. Then, do an in-place vertical blur. // * Horizontal only - blur horizontally copying values from the source to the destination. // * Vertical only - blur vertically copying values from the source to the destination.
// Initialize these assuming the Y-only case int loopStart = std::max(srcBounds.left(), dstBounds.left()); int loopEnd = std::min(srcBounds.right(), dstBounds.right()); int dstYOffset = 0;
if (makerX->window() > 1) { // First an X-only blur from src into dst, including the extra rows that will become // input for the second Y pass, which will then be performed in place.
loopStart = std::max(srcBounds.top(), dstBounds.top());
loopEnd = std::min(srcBounds.bottom(), dstBounds.bottom());
auto srcAddr = src.getAddr32(0, loopStart - srcBounds.top()); auto dstAddr = dst.getAddr32(0, loopStart - dstBounds.top());
// Iterate over each row to calculate 1D blur along X.
Pass* pass = makerX->makePass(buffer, &alloc); for (int y = loopStart; y < loopEnd; ++y) {
pass->blur(srcBounds.left() - dstBounds.left(),
srcBounds.right() - dstBounds.left(),
dstBounds.width(),
srcAddr, 1,
dstAddr, 1);
srcAddr += src.rowBytesAsPixels();
dstAddr += dst.rowBytesAsPixels();
}
// Set up the Y pass to blur from the full dst into the non-outset portion of dst
src = dst;
loopStart = originalDstBounds.left();
loopEnd = originalDstBounds.right(); // The new 'dst' is equal to dst.extractSubset(originalDstBounds.offset(-dstOrigin)), // but by construction only the Y offset has an interesting value so this is a little // more efficient.
dstYOffset = originalDstBounds.top() - dstBounds.top();
// Iterate over each column to calculate 1D blur along Y. This is either blurring from src // into dst for a 1D blur; or it's blurring from dst into dst for the second pass of a 2D // blur. if (makerY->window() > 1) { auto srcAddr = src.getAddr32(loopStart - srcBounds.left(), 0); auto dstAddr = dst.getAddr32(loopStart - dstBounds.left(), dstYOffset);
dstBounds = originalDstBounds.makeOffset(-dstOrigin); // Make relative to dst's pixels return SkSpecialImages::MakeFromRaster(dstBounds, dst, SkSurfaceProps{});
}
};
class RasterShaderBlurAlgorithm : public SkShaderBlurAlgorithm { public:
sk_sp<SkDevice> makeDevice(const SkImageInfo& imageInfo) const override { // This Device will only be used to draw blurs, so use default SkSurfaceProps. The pixel // geometry and font configuration do not matter. This is not a GPU surface, so DMSAA and // the kAlwaysDither surface property are also irrelevant. return SkBitmapDevice::Create(imageInfo, SkSurfaceProps{});
}
};
// If the sigma is larger than kBoxBlurMinSigma, we should assume that we won't encounter // an identity window assertion later on.
SkASSERT(SkBlurEngine::BoxBlurWindow(kBoxBlurMinSigma) > 1);
// Using the shader-based blur for small blur sigmas only happens if both axes require a // small blur. It's assumed that any inaccuracy along one axis is hidden by the large enough // blur along the other axis. constbool smallBlur = sigma.width() < kBoxBlurMinSigma &&
sigma.height() < kBoxBlurMinSigma; // The box blur doesn't actually care about channel order as long as it's 4 8-bit channels. constbool rgba8Blur = colorType == kRGBA_8888_SkColorType ||
colorType == kBGRA_8888_SkColorType; // TODO: Specialize A8 color types as well by reusing the mask filter blur impl if (smallBlur || !rgba8Blur) { return &fShaderBlurAlgorithm;
} else { return &fRGBA8BlurAlgorithm;
}
}
private: // For small sigmas and non-8888 or A8 color types, use the shader algorithm
RasterShaderBlurAlgorithm fShaderBlurAlgorithm; // For large blurs with RGBA8 or BGRA8, use consecutive box blurs
Raster8888BlurAlgorithm fRGBA8BlurAlgorithm;
};
void SkShaderBlurAlgorithm::Compute2DBlurKernel(SkSize sigma,
SkISize radius,
SkSpan<float> kernel) { // Callers likely had to calculate the radius prior to filling out the kernel value, which is // why it's provided; but make sure it's consistent with expectations.
SkASSERT(SkBlurEngine::SigmaToRadius(sigma.width()) == radius.width() &&
SkBlurEngine::SigmaToRadius(sigma.height()) == radius.height());
// Callers are responsible for downscaling large sigmas to values that can be processed by the // effects, so ensure the radius won't overflow 'kernel' constint width = KernelWidth(radius.width()); constint height = KernelWidth(radius.height()); const size_t kernelSize = SkTo<size_t>(sk_64_mul(width, height));
SkASSERT(kernelSize <= kernel.size());
// And the definition of an identity blur should be sufficient that 2sigma^2 isn't near zero // when there's a non-trivial radius. constfloat twoSigmaSqrdX = 2.0f * sigma.width() * sigma.width(); constfloat twoSigmaSqrdY = 2.0f * sigma.height() * sigma.height();
SkASSERT((radius.width() == 0 || !SkScalarNearlyZero(twoSigmaSqrdX)) &&
(radius.height() == 0 || !SkScalarNearlyZero(twoSigmaSqrdY)));
// Setting the denominator to 1 when the radius is 0 automatically converts the remaining math // to the 1D Gaussian distribution. When both radii are 0, it correctly computes a weight of 1.0 constfloat sigmaXDenom = radius.width() > 0 ? 1.0f / twoSigmaSqrdX : 1.f; constfloat sigmaYDenom = radius.height() > 0 ? 1.0f / twoSigmaSqrdY : 1.f;
float sum = 0.0f; for (int x = 0; x < width; x++) { float xTerm = static_cast<float>(x - radius.width());
xTerm = xTerm * xTerm * sigmaXDenom; for (int y = 0; y < height; y++) { float yTerm = static_cast<float>(y - radius.height()); float xyTerm = std::exp(-(xTerm + yTerm * yTerm * sigmaYDenom)); // Note that the constant term (1/(sqrt(2*pi*sigma^2)) of the Gaussian // is dropped here, since we renormalize the kernel below.
kernel[y * width + x] = xyTerm;
sum += xyTerm;
}
} // Normalize the kernel float scale = 1.0f / sum; for (size_t i = 0; i < kernelSize; ++i) {
kernel[i] *= scale;
} // Zero remainder of the array
memset(kernel.data() + kernelSize, 0, sizeof(float)*(kernel.size() - kernelSize));
}
// Given 2 adjacent gaussian points, they are blended as: Wi * Ci + Wj * Cj. // The GPU will mix Ci and Cj as Ci * (1 - x) + Cj * x during sampling. // Compute W', x such that W' * (Ci * (1 - x) + Cj * x) = Wi * Ci + Wj * Cj. // Solving W' * x = Wj, W' * (1 - x) = Wi: // W' = Wi + Wj // x = Wj / (Wi + Wj) auto get_new_weight = [](float* new_w, float* offset, float wi, float wj) {
*new_w = wi + wj;
*offset = wj / (wi + wj);
};
// Create a temporary standard kernel. The maximum blur radius that can be passed to this // function is (kMaxBlurSamples-1), so make an array large enough to hold the full kernel width. static constexpr int kMaxKernelWidth = KernelWidth(kMaxSamples - 1);
SkASSERT(KernelWidth(radius) <= kMaxKernelWidth);
std::array<float, kMaxKernelWidth> fullKernel;
Compute1DBlurKernel(sigma, radius, SkSpan<float>{fullKernel.data(), KernelWidth(radius)});
std::array<float, kMaxSamples> kernel;
std::array<float, kMaxSamples> offsets; // Note that halfsize isn't just size / 2, but radius + 1. This is the size of the output array. int halfSize = LinearKernelWidth(radius); int halfRadius = halfSize / 2; int lowIndex = halfRadius - 1;
// Compute1DGaussianKernel produces a full 2N + 1 kernel. Since the kernel can be mirrored, // compute only the upper half and mirror to the lower half.
int index = radius; if (radius & 1) { // If N is odd, then use two samples. // The centre texel gets sampled twice, so halve its influence for each sample. // We essentially sample like this: // Texel edges // v v v v // | | | | // \-----^---/ Lower sample // \---^-----/ Upper sample
get_new_weight(&kernel[halfRadius],
&offsets[halfRadius],
fullKernel[index] * 0.5f,
fullKernel[index + 1]);
kernel[lowIndex] = kernel[halfRadius];
offsets[lowIndex] = -offsets[halfRadius];
index++;
lowIndex--;
} else { // If N is even, then there are an even number of texels on either side of the centre texel. // Sample the centre texel directly.
kernel[halfRadius] = fullKernel[index];
offsets[halfRadius] = 0.0f;
}
index++;
// Every other pair gets one sample. for (int i = halfRadius + 1; i < halfSize; index += 2, i++, lowIndex--) {
get_new_weight(&kernel[i], &offsets[i], fullKernel[index], fullKernel[index + 1]);
offsets[i] += static_cast<float>(index - radius);
// Zero out remaining values in the kernel
memset(kernel.data() + halfSize, 0, sizeof(float)*(kMaxSamples - halfSize)); // But copy the last valid offset into the remaining offsets, to increase the chance that // over-iteration in a fragment shader will have a cache hit. for (int i = halfSize; i < kMaxSamples; ++i) {
offsets[i] = offsets[halfSize - 1];
}
// Interleave into the output array to match the 1D SkSL effect for (int i = 0; i < kMaxSamples / 2; ++i) {
offsetsAndKernel[i] = SkV4{offsets[2*i], kernel[2*i], offsets[2*i+1], kernel[2*i+1]};
}
}
static SkKnownRuntimeEffects::StableKey to_stablekey(int kernelWidth, uint32_t baseKey) {
SkASSERT(kernelWidth >= 2 && kernelWidth <= SkShaderBlurAlgorithm::kMaxSamples); switch(kernelWidth) { // Batch on multiples of 4 (skipping width=1, since that can't happen) case 2: [[fallthrough]]; case 3: [[fallthrough]]; case 4: returnstatic_cast<SkKnownRuntimeEffects::StableKey>(baseKey); case 5: [[fallthrough]]; case 6: [[fallthrough]]; case 7: [[fallthrough]]; case 8: returnstatic_cast<SkKnownRuntimeEffects::StableKey>(baseKey+1); case 9: [[fallthrough]]; case 10: [[fallthrough]]; case 11: [[fallthrough]]; case 12: returnstatic_cast<SkKnownRuntimeEffects::StableKey>(baseKey+2); case 13: [[fallthrough]]; case 14: [[fallthrough]]; case 15: [[fallthrough]]; case 16: returnstatic_cast<SkKnownRuntimeEffects::StableKey>(baseKey+3); case 17: [[fallthrough]]; case 18: [[fallthrough]]; case 19: [[fallthrough]]; // With larger kernels, batch on multiples of eight so up to 7 wasted samples. case 20: returnstatic_cast<SkKnownRuntimeEffects::StableKey>(baseKey+4); case 21: [[fallthrough]]; case 22: [[fallthrough]]; case 23: [[fallthrough]]; case 24: [[fallthrough]]; case 25: [[fallthrough]]; case 26: [[fallthrough]]; case 27: [[fallthrough]]; case 28: returnstatic_cast<SkKnownRuntimeEffects::StableKey>(baseKey+5); default:
SkUNREACHABLE;
}
}
// renderBlur() will either mix multiple fast and strict draws to cover dstRect, or will issue // a single strict draw. While the SkShader object changes (really just strict mode), the rest // of the SkPaint remains the same.
SkPaint paint;
paint.setBlendMode(SkBlendMode::kSrc);
// Only consider the safeSrcRect for shader-based tiling if the original srcRect is different // from the backing store dimensions; when they match the full image we can use HW tiling. if (srcRect != SkIRect::MakeSize(input->backingStoreDimensions())) { if (fastDstRect.intersect(safeSrcRect)) { // If the area of the non-clamping shader is small, it's better to just issue a single // draw that performs shader tiling over the whole dst. if (fastDstRect != dstRect && fastDstRect.width() * fastDstRect.height() < 128 * 128) {
fastDstRect.setEmpty();
}
} else {
fastDstRect.setEmpty();
}
}
if (!fastDstRect.isEmpty()) { // Fill as much as possible without adding shader tiling logic to each blur sample, // switching to clamp tiling if we aren't in this block due to HW tiling.
SkIRect untiledSrcRect = srcRect.makeInset(1, 1);
SkTileMode fastTileMode = untiledSrcRect.contains(fastDstRect) ? SkTileMode::kClamp
: tileMode;
blurEffectBuilder->child("child") = input->asShader(
fastTileMode, filter, SkMatrix::I(), /*strict=*/false);
paint.setShader(blurEffectBuilder->makeShader());
device->drawRect(SkRect::Make(fastDstRect), paint);
}
// Switch to a strict shader if there are remaining pixels to fill if (fastDstRect != dstRect) {
blurEffectBuilder->child("child") = input->makeSubset(srcRect)->asShader(
tileMode, filter, SkMatrix::Translate(srcRect.left(), srcRect.top()));
paint.setShader(blurEffectBuilder->makeShader());
}
if (fastDstRect.isEmpty()) { // Fill the entire dst with the strict shader
device->drawRect(SkRect::Make(dstRect), paint);
} elseif (fastDstRect != dstRect) { // There will be up to four additional strict draws to fill in the border. The left and // right sides will span the full height of the dst rect. The top and bottom will span // the just the width of the fast interior. Strict border draws with zero width/height // are skipped. auto drawBorder = [&](const SkIRect& r) { if (!r.isEmpty()) {
device->drawRect(SkRect::Make(r), paint);
}
};
int radiusX = SkBlurEngine::SigmaToRadius(sigma.width()); int radiusY = SkBlurEngine::SigmaToRadius(sigma.height()); constint kernelArea = KernelWidth(radiusX) * KernelWidth(radiusY); if (kernelArea <= kMaxSamples && radiusX > 0 && radiusY > 0) { // Use a single-pass 2D kernel if it fits and isn't just 1D already return this->evalBlur2D(sigma,
{radiusX, radiusY},
std::move(src),
srcRect,
tileMode,
dstRect);
} else { // Use two passes of a 1D kernel (one per axis).
SkIRect intermediateSrcRect = srcRect;
SkIRect intermediateDstRect = dstRect; if (radiusX > 0) { if (radiusY > 0) { // May need to maintain extra rows above and below 'dstRect' for the follow-up pass. if (tileMode == SkTileMode::kRepeat || tileMode == SkTileMode::kMirror) { // If the srcRect and dstRect are aligned, then we don't need extra rows since // the periodic tiling on srcRect is the same for the intermediate. If they // are not aligned, then outset by the Y radius. constint period = srcRect.height() * (tileMode == SkTileMode::kMirror ? 2 : 1); if (std::abs(dstRect.fTop - srcRect.fTop) % period != 0 ||
dstRect.height() != srcRect.height()) {
intermediateDstRect.outset(0, radiusY);
}
} else { // For clamp and decal tiling, we outset by the Y radius up to what's available // from the srcRect. Anything beyond that is identical to tiling the // intermediate dst image directly.
intermediateDstRect.outset(0, radiusY);
intermediateDstRect.fTop = std::max(intermediateDstRect.fTop, srcRect.fTop);
intermediateDstRect.fBottom =
std::min(intermediateDstRect.fBottom, srcRect.fBottom); if (intermediateDstRect.fTop >= intermediateDstRect.fBottom) { return nullptr;
}
}
}
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