Use combined three pass code for image blur.

This changes more closely matches the GL output, and the runtimes are similar or
faster for the common cases.

x86_64 times:
benchmark                            old-Us   new-Us   old/new
blur_image_filter_large_80.00_80.00  4842.04  2626.10  1.84381
blur_image_filter_small_80.00_80.00  3297.72  854.97   3.85712
blur_image_filter_large_10.00_10.00  930.44   720.50   1.29138
blur_image_filter_small_10.00_10.00  69.96    42.15    1.65979
blur_image_filter_large_1.00_1.00    682.66   521.78   1.30833
blur_image_filter_small_1.00_1.00    19.21    14.43    1.33125
blur_image_filter_large_0.50_0.50    696.17   64.14    10.8539
blur_image_filter_small_0.50_0.50    16.26    5.02     3.23904

arm64 times:
benchmark                            old-Us    new-Us    old/new
blur_image_filter_large_80.00_80.00  42144.53  14128.42  2.98296
blur_image_filter_small_80.00_80.00  24840.58  4392.58   5.65512
blur_image_filter_large_10.00_10.00  3556.40   3793.70   0.937449
blur_image_filter_small_10.00_10.00  282.53    220.62    1.28062
blur_image_filter_large_1.00_1.00    2502.20   2937.99   0.851671
blur_image_filter_small_1.00_1.00    83.32     81.93     1.01697
blur_image_filter_large_0.50_0.50    5643.80   272.83    20.6861
blur_image_filter_small_0.50_0.50    141.02    38.29     3.68295

Cq-Include-Trybots: skia.primary:Test-Debian9-Clang-GCE-CPU-AVX2-x86_64-Release-All-SKNX_NO_SIMD
Change-Id: Ic53b3186607d5485477b92e4ca7b092bf1366c52
Reviewed-on: https://skia-review.googlesource.com/52771
Commit-Queue: Herb Derby <herb@google.com>
Reviewed-by: Mike Klein <mtklein@google.com>
This commit is contained in:
Herb Derby 2017-10-17 10:37:09 -04:00 committed by Skia Commit-Bot
parent 9eca72b57b
commit d4a0fc7383
2 changed files with 379 additions and 24 deletions

View File

@ -7,11 +7,16 @@
#include "SkBlurImageFilter.h"
#include <algorithm>
#include "SkArenaAlloc.h"
#include "SkAutoPixmapStorage.h"
#include "SkBitmap.h"
#include "SkColorData.h"
#include "SkColorSpaceXformer.h"
#include "SkTFitsIn.h"
#include "SkGpuBlurUtils.h"
#include "SkNx.h"
#include "SkOpts.h"
#include "SkReadBuffer.h"
#include "SkSpecialImage.h"
@ -23,13 +28,18 @@
#include "SkGr.h"
#endif
// The value where the three pass window calculation results in a zero window.
// N[Solve[sigma*3*Sqrt[2 Pi]/4 == 1/2, sigma], 16]
static constexpr double kZeroWindow = 0.26596152026762;
static constexpr double kPi = 3.14159265358979323846264338327950288;
class SkBlurImageFilterImpl final : public SkImageFilter {
public:
SkBlurImageFilterImpl(SkScalar sigmaX,
SkScalar sigmaY,
sk_sp<SkImageFilter> input,
const CropRect* cropRect,
SkBlurImageFilter::TileMode tileMode);
SkScalar sigmaY,
sk_sp<SkImageFilter> input,
const CropRect* cropRect,
SkBlurImageFilter::TileMode tileMode);
SkRect computeFastBounds(const SkRect&) const override;
@ -162,6 +172,342 @@ static void get_box3_params(SkScalar s, int *kernelSize, int* kernelSize3, int *
}
}
#if !defined(SK_SUPPORT_LEGACY_BLUR_IMAGE)
// This is defined by the SVG spec:
// https://drafts.fxtf.org/filter-effects/#feGaussianBlurElement
static int calculate_window(double sigma) {
// 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.
sigma = SkTPin(sigma, 0.0, 136.0);
auto possibleWindow = static_cast<int>(floor(sigma * 3 * sqrt(2 * kPi) / 4 + 0.5));
return std::max(1, possibleWindow);
}
// 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.
static int calculate_border(int window) {
return (window & 1) == 1 ? 3 * ((window - 1) / 2) : 3 * (window / 2) - 1;
}
static int calculate_buffer(int window) {
int bufferSize = window - 1;
return (window & 1) == 1 ? 3 * bufferSize : 3 * bufferSize + 1;
}
// blur_one_direction 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
//
// This is all encapsulated in the processValue function below.
//
using Pass0And1 = Sk4u[2];
// The would be dLeft parameter is assumed to be 0.
static void blur_one_direction(Sk4u* buffer, int window,
int srcLeft, int srcRight, int dstRight,
const uint32_t* src, int srcXStride, int srcYStride, int srcH,
uint32_t* dst, int dstXStride, int dstYStride) {
// The circular buffers are one less than the window.
auto pass0Count = window - 1,
pass1Count = window - 1,
pass2Count = (window & 1) == 1 ? window - 1 : window;
Pass0And1* buffer01Start = (Pass0And1*)buffer;
Sk4u* buffer2Start = buffer + pass0Count + pass1Count;
Pass0And1* buffer01End = (Pass0And1*)buffer2Start;
Sk4u* buffer2End = buffer2Start + pass2Count;
// If the window is odd then the divisor is just window ^ 3 otherwise,
// it is window * window * (window + 1) = window ^ 3 + window ^ 2;
auto window2 = window * window;
auto window3 = window2 * window;
auto divisor = (window & 1) == 1 ? window3 : window3 + window2;
// NB the sums in the blur code use the following technique to avoid
// adding 1/2 to round the divide.
//
// Sum/d + 1/2 == (Sum + h) / d
// Sum + d(1/2) == Sum + h
// h == (1/2)d
//
// But the d/2 it self should be rounded.
// h == d/2 + 1/2 == (d + 1) / 2
//
// weight = 1 / d * 2 ^ 32
auto weight = static_cast<uint32_t>(round(1.0 / divisor * (1ull << 32)));
auto half = static_cast<uint32_t>((divisor + 1) / 2);
auto border = calculate_border(window);
// Calculate the start and end of the source pixels with respect to the destination start.
auto srcStart = srcLeft - border,
srcEnd = srcRight - border,
dstEnd = dstRight;
for (auto y = 0; y < srcH; y++) {
auto buffer01Cursor = buffer01Start;
auto buffer2Cursor = buffer2Start;
Sk4u sum0{0u};
Sk4u sum1{0u};
Sk4u sum2{half};
sk_bzero(buffer01Start, (buffer2End - (Sk4u *) (buffer01Start)) * sizeof(*buffer2Start));
// Given an expanded input pixel, move the window ahead using the leadingEdge value.
auto processValue = [&](const Sk4u& leadingEdge) -> Sk4u {
sum0 += leadingEdge;
sum1 += sum0;
sum2 += sum1;
Sk4u value = sum2.mulHi(weight);
sum2 -= *buffer2Cursor;
*buffer2Cursor = sum1;
buffer2Cursor = (buffer2Cursor + 1) < buffer2End ? buffer2Cursor + 1 : buffer2Start;
sum1 -= (*buffer01Cursor)[1];
(*buffer01Cursor)[1] = sum0;
sum0 -= (*buffer01Cursor)[0];
(*buffer01Cursor)[0] = leadingEdge;
buffer01Cursor =
(buffer01Cursor + 1) < buffer01End ? buffer01Cursor + 1 : buffer01Start;
return value;
};
auto srcIdx = srcStart;
auto dstIdx = 0;
const uint32_t* srcCursor = src;
uint32_t* dstCursor = dst;
// The destination pixels are not effected by the src pixels,
// change to zero as per the spec.
// https://drafts.fxtf.org/filter-effects/#FilterPrimitivesOverviewIntro
while (dstIdx < srcIdx) {
*dstCursor = 0;
dstCursor += dstXStride;
SK_PREFETCH(dstCursor);
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.
while (dstIdx > srcIdx) {
Sk4u leadingEdge = srcIdx < srcEnd ? SkNx_cast<uint32_t>(Sk4b::Load(srcCursor)) : 0;
(void) processValue(leadingEdge);
srcCursor += srcXStride;
srcIdx++;
}
// The dstIdx and srcIdx are in sync now; the code just uses the dstIdx for both now.
// Consume the source generating pixels to dst.
auto loopEnd = std::min(dstEnd, srcEnd);
while (dstIdx < loopEnd) {
Sk4u leadingEdge = SkNx_cast<uint32_t>(Sk4b::Load(srcCursor));
SkNx_cast<uint8_t>(processValue(leadingEdge)).store(dstCursor);
srcCursor += srcXStride;
dstCursor += dstXStride;
SK_PREFETCH(dstCursor);
dstIdx++;
}
// The leading edge is beyond the end of the source. Assume that the pixels
// are now 0x0000 until the end of the destination.
loopEnd = dstEnd;
while (dstIdx < loopEnd) {
SkNx_cast<uint8_t>(processValue(0u)).store(dstCursor);
dstCursor += dstXStride;
SK_PREFETCH(dstCursor);
dstIdx++;
}
src += srcYStride;
dst += dstYStride;
}
}
static sk_sp<SkSpecialImage> combined_pass_blur(
SkVector sigma,
SkSpecialImage* source, const sk_sp<SkSpecialImage>& input,
SkIRect inputBounds, SkIRect dstBounds) {
SkBitmap inputBM;
if (!input->getROPixels(&inputBM)) {
return nullptr;
}
if (inputBM.colorType() != kN32_SkColorType) {
return nullptr;
}
SkBitmap src;
inputBM.extractSubset(&src, inputBounds);
// Make everything relative to the destination bounds.
inputBounds.offset(-dstBounds.x(), -dstBounds.y());
dstBounds.offset( -dstBounds.x(), -dstBounds.y());
auto windowW = calculate_window(sigma.x()),
windowH = calculate_window(sigma.y());
auto srcW = inputBounds.width(),
srcH = inputBounds.height(),
dstW = dstBounds.width(),
dstH = dstBounds.height();
SkImageInfo dstInfo = SkImageInfo::Make(dstW, dstH, inputBM.colorType(), inputBM.alphaType());
SkBitmap dst;
if (!dst.tryAllocPixels(dstInfo)) {
return nullptr;
}
auto bufferSizeW = calculate_buffer(windowW),
bufferSizeH = calculate_buffer(windowH);
// The amount 1024 is enough for buffers up to 10 sigma. The tmp bitmap will be
// allocated on the heap.
SkSTArenaAlloc<1024> alloc;
Sk4u* buffer = alloc.makeArrayDefault<Sk4u>(std::max(bufferSizeW, bufferSizeH));
if (windowW > 1 && windowH > 1) {
// Blur both directions.
auto tmpW = srcH,
tmpH = dstW;
auto tmp = alloc.makeArrayDefault<uint32_t>(tmpW * tmpH);
// Blur horizontally, and transpose.
blur_one_direction(
buffer, windowW,
inputBounds.left(), inputBounds.right(), dstBounds.right(),
static_cast<uint32_t*>(src.getPixels()), 1, src.rowBytesAsPixels(), srcH,
tmp, tmpW, 1);
// Blur vertically (scan in memory order because of the transposition),
// and transpose back to the original orientation.
blur_one_direction(
buffer, windowH,
inputBounds.top(), inputBounds.bottom(), dstBounds.bottom(),
tmp, 1, tmpW, tmpH,
static_cast<uint32_t*>(dst.getPixels()), dst.rowBytesAsPixels(), 1);
} else if (windowW > 1) {
// Blur only horizontally.
blur_one_direction(
buffer, windowW,
inputBounds.left(), inputBounds.right(), dstBounds.right(),
static_cast<uint32_t*>(src.getPixels()), 1, src.rowBytesAsPixels(), srcH,
static_cast<uint32_t*>(dst.getPixels()), 1, dst.rowBytesAsPixels());
} else if (windowH > 1) {
// Blur only vertically.
blur_one_direction(
buffer, windowH,
inputBounds.top(), inputBounds.bottom(), dstBounds.bottom(),
static_cast<uint32_t*>(src.getPixels()), src.rowBytesAsPixels(), 1, srcW,
static_cast<uint32_t*>(dst.getPixels()), dst.rowBytesAsPixels(), 1);
} else {
// Nothing to do.
return input->makeSubset(inputBounds);
}
return SkSpecialImage::MakeFromRaster(SkIRect::MakeWH(dstBounds.width(),
dstBounds.height()),
dst, &source->props());
}
#endif
sk_sp<SkSpecialImage> SkBlurImageFilterImpl::onFilterImage(SkSpecialImage* source,
const Context& ctx,
SkIPoint* offset) const {
@ -207,12 +553,16 @@ sk_sp<SkSpecialImage> SkBlurImageFilterImpl::onFilterImage(SkSpecialImage* sourc
} else
#endif
{
#if defined(SK_SUPPORT_LEGACY_BLUR_IMAGE)
result = this->cpuFilter(source, sigma, input, inputBounds, dstBounds);
#else
// The new code will go here.
result = this->cpuFilter(source, sigma, input, inputBounds, dstBounds);
#endif
// If both sigmas will result in a zero width window, there is nothing to do.
if (sigma.x() < kZeroWindow && sigma.y() < kZeroWindow) {
result = input->makeSubset(inputBounds);
} else {
#if defined(SK_SUPPORT_LEGACY_BLUR_IMAGE)
result = this->cpuFilter(source, sigma, input, inputBounds, dstBounds);
#else
result = combined_pass_blur(sigma, source, input, inputBounds, dstBounds);
#endif
}
}
// Return the resultOffset if the blur succeeded.
@ -235,8 +585,8 @@ sk_sp<SkSpecialImage> SkBlurImageFilterImpl::gpuFilter(
// The raw cross arm value c = E^-s
// The normalized cross arm value = c/n
// N[Solve[{c/n == 1/2048, sigma > 0}, sigma], 16]
static constexpr double kCrossTooSmall = 0.2561130112451658;
if (sigma.x() < kCrossTooSmall && sigma.y() < kCrossTooSmall) {
static constexpr double kZeroWindowGPU = 0.2561130112451658;
if (sigma.x() < kZeroWindowGPU && sigma.y() < kZeroWindowGPU) {
return input->makeSubset(inputBounds);
}
@ -280,13 +630,6 @@ sk_sp<SkSpecialImage> SkBlurImageFilterImpl::cpuFilter(
SkVector sigma, const sk_sp<SkSpecialImage> &input,
SkIRect inputBounds, SkIRect dstBounds) const
{
// If both sigmas will result in a zero width window, there is nothing to do.
// N[Solve[sigma*3*Sqrt[2 Pi]/4 == 1/2, sigma], 16]
static constexpr double kZeroWindow = 0.2659615202676218;
if (sigma.x() < kZeroWindow && sigma.y() < kZeroWindow) {
return input->makeSubset(inputBounds);
}
int kernelSizeX, kernelSizeX3, lowOffsetX, highOffsetX;
int kernelSizeY, kernelSizeY3, lowOffsetY, highOffsetY;
get_box3_params(sigma.x(), &kernelSizeX, &kernelSizeX3, &lowOffsetX, &highOffsetX);
@ -376,14 +719,26 @@ const {
SkRect SkBlurImageFilterImpl::computeFastBounds(const SkRect& src) const {
SkRect bounds = this->getInput(0) ? this->getInput(0)->computeFastBounds(src) : src;
#if defined(SK_SUPPORT_LEGACY_BLUR_IMAGE)
bounds.outset(fSigma.width() * 3, fSigma.height() * 3);
#else
auto borderW = calculate_border(calculate_window(fSigma.width())),
borderH = calculate_border(calculate_window(fSigma.height()));
bounds.outset(borderW, borderH);
#endif
return bounds;
}
SkIRect SkBlurImageFilterImpl::onFilterNodeBounds(const SkIRect& src, const SkMatrix& ctm,
MapDirection) const {
SkVector sigma = map_sigma(fSigma, ctm);
#if defined(SK_SUPPORT_LEGACY_BLUR_IMAGE)
return src.makeOutset(SkScalarCeilToInt(sigma.x() * 3), SkScalarCeilToInt(sigma.y() * 3));
#else
auto borderW = calculate_border(calculate_window(sigma.x())),
borderH = calculate_border(calculate_window(sigma.y()));
return src.makeOutset(borderW, borderH);
#endif
}
#ifndef SK_IGNORE_TO_STRING

View File

@ -853,7 +853,7 @@ DEF_TEST(ImageFilterBlurThenShadowBounds, reporter) {
sk_sp<SkImageFilter> filter2(make_drop_shadow(std::move(filter1)));
SkIRect bounds = SkIRect::MakeXYWH(0, 0, 100, 100);
SkIRect expectedBounds = SkIRect::MakeXYWH(-133, -133, 236, 236);
SkIRect expectedBounds = SkIRect::MakeXYWH(-132, -132, 234, 234);
bounds = filter2->filterBounds(bounds, SkMatrix::I());
REPORTER_ASSERT(reporter, bounds == expectedBounds);
@ -864,7 +864,7 @@ DEF_TEST(ImageFilterShadowThenBlurBounds, reporter) {
sk_sp<SkImageFilter> filter2(make_blur(std::move(filter1)));
SkIRect bounds = SkIRect::MakeXYWH(0, 0, 100, 100);
SkIRect expectedBounds = SkIRect::MakeXYWH(-133, -133, 236, 236);
SkIRect expectedBounds = SkIRect::MakeXYWH(-132, -132, 234, 234);
bounds = filter2->filterBounds(bounds, SkMatrix::I());
REPORTER_ASSERT(reporter, bounds == expectedBounds);
@ -893,7 +893,7 @@ DEF_TEST(ImageFilterScaledBlurRadius, reporter) {
scaleMatrix.setScale(2, 2);
SkIRect bounds = SkIRect::MakeLTRB(0, 0, 200, 200);
SkIRect expectedBlurBounds = SkIRect::MakeLTRB(-6, -6, 206, 206);
SkIRect expectedBlurBounds = SkIRect::MakeLTRB(-5, -5, 205, 205);
SkIRect blurBounds = blur->filterBounds(
bounds, scaleMatrix, SkImageFilter::kForward_MapDirection);
REPORTER_ASSERT(reporter, blurBounds == expectedBlurBounds);
@ -918,7 +918,7 @@ DEF_TEST(ImageFilterScaledBlurRadius, reporter) {
scaleMatrix.setScale(1, -1);
SkIRect bounds = SkIRect::MakeLTRB(0, -100, 100, 0);
SkIRect expectedBlurBounds = SkIRect::MakeLTRB(-3, -103, 103, 3);
SkIRect expectedBlurBounds = SkIRect::MakeLTRB(-2, -102, 102, 2);
SkIRect blurBounds = blur->filterBounds(
bounds, scaleMatrix, SkImageFilter::kForward_MapDirection);
REPORTER_ASSERT(reporter, blurBounds == expectedBlurBounds);
@ -947,7 +947,7 @@ DEF_TEST(ImageFilterComposedBlurFastBounds, reporter) {
SkRect boundsSrc = SkRect::MakeWH(SkIntToScalar(100), SkIntToScalar(100));
SkRect expectedBounds = SkRect::MakeXYWH(
SkIntToScalar(-6), SkIntToScalar(-6), SkIntToScalar(112), SkIntToScalar(112));
SkIntToScalar(-4), SkIntToScalar(-4), SkIntToScalar(108), SkIntToScalar(108));
SkRect boundsDst = composedFilter->computeFastBounds(boundsSrc);
REPORTER_ASSERT(reporter, boundsDst == expectedBounds);