src/core/SkMaskBlurFilter.cpp - skia - Git at Google

 /*
  * Copyright 2017 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */

 #include "SkMaskBlurFilter.h"

 #include <cmath>

 #include "SkMakeUnique.h"

 static const double kPi = 3.14159265358979323846264338327950288;

 static uint64_t weight_from_diameter(uint32_t d) {
     uint64_t d2 = d * d;
     uint64_t d3 = d2 * d;
     if ((d&1) == 0) {
         // d * d * (d + 1);
         return d3 + d2;
     }

     return d3;
 }

 static uint32_t filter_window(double sigma) {
     auto possibleWindow = static_cast<uint32_t>(floor(sigma * 3 * sqrt(2*kPi)/4 + 0.5));
     return std::max(1u, possibleWindow);
 }

 SkMaskBlurFilter::FilterInfo::FilterInfo(double sigma)
     : fFilterWindow{filter_window(sigma)}
     , fScaledWeight{(static_cast<uint64_t>(1) << 32) / weight_from_diameter(fFilterWindow)} {}

 uint64_t SkMaskBlurFilter::FilterInfo::weight() const {
     return weight_from_diameter(fFilterWindow);

 }
 uint32_t SkMaskBlurFilter::FilterInfo::borderSize() const {
     if ((fFilterWindow&1) == 0) {
         return 3 * (fFilterWindow / 2) - 1;
     }
     return 3 * (fFilterWindow / 2);
 }

 size_t SkMaskBlurFilter::FilterInfo::diameter(uint8_t pass) const {
     SkASSERT(pass <= 2);

     if ((fFilterWindow&1) == 0) {
         // Handle even case.
         switch (pass) {
             case 0: return fFilterWindow;
             case 1: return fFilterWindow;
             case 2: return fFilterWindow+1;
         }
     }

     return fFilterWindow;
 }

 uint64_t SkMaskBlurFilter::FilterInfo::scaledWeight() const {
     return fScaledWeight;
 }

 SkMaskBlurFilter::SkMaskBlurFilter(double sigmaW, double sigmaH)
     : fInfoW{sigmaW}, fInfoH{sigmaH}
     , fBuffer0{skstd::make_unique_default<uint32_t[]>(bufferSize(0))}
     , fBuffer1{skstd::make_unique_default<uint32_t[]>(bufferSize(1))}
     , fBuffer2{skstd::make_unique_default<uint32_t[]>(bufferSize(2))} {
 }

 SkIPoint SkMaskBlurFilter::blur(const SkMask& src, SkMask* dst) const {

     uint64_t weightW = fInfoW.weight();
     uint64_t weightH = fInfoH.weight();

     size_t borderW = fInfoW.borderSize();
     size_t borderH = fInfoH.borderSize();

     size_t srcW = src.fBounds.width();
     size_t srcH = src.fBounds.height();

     size_t dstW = srcW + 2 * borderW;
     size_t dstH = srcH + 2 * borderH;

     dst->fBounds.set(0, 0, dstW, dstH);
     dst->fBounds.offset(src.fBounds.x(), src.fBounds.y());
     dst->fBounds.offset(-SkTo<int32_t>(borderW), -SkTo<int32_t>(borderH));

     dst->fImage = nullptr;
     dst->fRowBytes = dstW;
     dst->fFormat = SkMask::kA8_Format;

     if (src.fImage == nullptr) {
         return {SkTo<int32_t>(borderW), SkTo<int32_t>(borderH)};
     }

     dst->fImage = SkMask::AllocImage(dstW * dstH);

     if (weightW > 1 && weightH > 1) {
         // Blur both directions.
         size_t tmpW = srcH;
         size_t tmpH = dstW;
         auto tmp = skstd::make_unique_default<uint8_t[]>(tmpW * tmpH);

         // Blur horizontally, and transpose.
         for (size_t y = 0; y < srcH; y++) {
             auto srcStart = &src.fImage[y * src.fRowBytes];
             auto tmpStart = &tmp[y];
             this->blurOneScan(fInfoW,
                               srcStart, 1, srcStart + srcW,
                               tmpStart, tmpW, tmpStart + tmpW * tmpH);
         }

         // Blur vertically (scan in memory order because of the transposition),
         // and transpose back to the original orientation.
         for (size_t y = 0; y < tmpH; y++) {
             auto tmpStart = &tmp[y * tmpW];
             auto dstStart = &dst->fImage[y];
             this->blurOneScan(fInfoH,
                               tmpStart, 1, tmpStart + tmpW,
                               dstStart, dst->fRowBytes, dstStart + dst->fRowBytes * dstH);
         }
     } else if (weightW > 1) {
         // Blur only horizontally.

         for (size_t y = 0; y < srcH; y++) {
             auto srcStart = &src.fImage[y * src.fRowBytes];
             auto dstStart = &dst->fImage[y * dst->fRowBytes];
             this->blurOneScan(fInfoW,
                               srcStart, 1, srcStart + srcW,
                               dstStart, 1, dstStart + dstW);
         }
     } else if (weightH > 1) {
         // Blur only vertically.

         for (size_t x = 0; x < srcW; x++) {
             auto srcStart = &src.fImage[x];
             auto srcEnd   = &src.fImage[src.fRowBytes * srcH];
             auto dstStart = &dst->fImage[x];
             auto dstEnd   = &dst->fImage[dst->fRowBytes * dstH];
             this->blurOneScan(fInfoH,
                               srcStart, src.fRowBytes, srcEnd,
                               dstStart, dst->fRowBytes, dstEnd);
         }
     } else {
         // Copy to dst. No Blur.

         for (size_t y = 0; y < srcH; y++) {
             std::memcpy(&dst->fImage[y * dst->fRowBytes], &src.fImage[y * src.fRowBytes], dstW);
         }
     }

     return {SkTo<int32_t>(borderW), SkTo<int32_t>(borderH)};
 }

 size_t SkMaskBlurFilter::bufferSize(uint8_t bufferPass) const {
     return std::max(fInfoW.diameter(bufferPass), fInfoH.diameter(bufferPass)) - 1;
 }

 // Blur one horizontal scan into the dst.
 void SkMaskBlurFilter::blurOneScan(
     FilterInfo info,
     const uint8_t* src, size_t srcStride, const uint8_t* srcEnd,
           uint8_t* dst, size_t dstStride,       uint8_t* dstEnd) const {

     auto buffer0Begin = &fBuffer0[0];
     auto buffer1Begin = &fBuffer1[0];
     auto buffer2Begin = &fBuffer2[0];

     auto buffer0Cursor = buffer0Begin;
     auto buffer1Cursor = buffer1Begin;
     auto buffer2Cursor = buffer2Begin;

     auto buffer0End = &fBuffer0[0] + info.diameter(0) - 1;
     auto buffer1End = &fBuffer1[0] + info.diameter(1) - 1;
     auto buffer2End = &fBuffer2[0] + info.diameter(2) - 1;

     std::memset(&fBuffer0[0], 0, (buffer0End - buffer0Begin) * sizeof(fBuffer0[0]));
     std::memset(&fBuffer1[0], 0, (buffer1End - buffer1Begin) * sizeof(fBuffer1[0]));
     std::memset(&fBuffer2[0], 0, (buffer2End - buffer2Begin) * sizeof(fBuffer2[0]));

     uint32_t sum0 = 0;
     uint32_t sum1 = 0;
     uint32_t sum2 = 0;

     const uint64_t half = static_cast<uint64_t>(1) << 31;

     // Consume the source generating pixels.
     for (auto srcCursor = src; srcCursor < srcEnd; dst += dstStride, srcCursor += srcStride) {
         uint32_t s = *srcCursor;
         sum0 += s;
         sum1 += sum0;
         sum2 += sum1;

         *dst = SkTo<uint8_t>((info.scaledWeight() * sum2 + half) >> 32);

         sum2 -= *buffer2Cursor;
         *buffer2Cursor = sum1;
         buffer2Cursor = (buffer2Cursor + 1) < buffer2End ? buffer2Cursor + 1 : &fBuffer2[0];

         sum1 -= *buffer1Cursor;
         *buffer1Cursor = sum0;
         buffer1Cursor = (buffer1Cursor + 1) < buffer1End ? buffer1Cursor + 1 : &fBuffer1[0];

         sum0 -= *buffer0Cursor;
         *buffer0Cursor = s;
         buffer0Cursor = (buffer0Cursor + 1) < buffer0End ? buffer0Cursor + 1 : &fBuffer0[0];
     }

     // This handles the case when both ends of the box are not between [src, srcEnd), and both
     // are zero at that point.
     for (auto i = 0; i < static_cast<ptrdiff_t>(2 * info.borderSize()) - (srcEnd - src); i++) {
         uint32_t s = 0;
         sum0 += s;
         sum1 += sum0;
         sum2 += sum1;

         *dst = SkTo<uint8_t>((info.scaledWeight() * sum2 + half) >> 32);

         sum2 -= *buffer2Cursor;
         *buffer2Cursor = sum1;
         buffer2Cursor = (buffer2Cursor + 1) < buffer2End ? buffer2Cursor + 1 : &fBuffer2[0];

         sum1 -= *buffer1Cursor;
         *buffer1Cursor = sum0;
         buffer1Cursor = (buffer1Cursor + 1) < buffer1End ? buffer1Cursor + 1 : &fBuffer1[0];

         sum0 -= *buffer0Cursor;
         *buffer0Cursor = s;
         buffer0Cursor = (buffer0Cursor + 1) < buffer0End ? buffer0Cursor + 1 : &fBuffer0[0];
         dst += dstStride;
     }

     // Starting from the right, fill in the rest of the buffer.
     std::memset(&fBuffer0[0], 0, (buffer0End - &fBuffer0[0]) * sizeof(fBuffer0[0]));
     std::memset(&fBuffer1[0], 0, (buffer1End - &fBuffer1[0]) * sizeof(fBuffer1[0]));
     std::memset(&fBuffer2[0], 0, (buffer2End - &fBuffer2[0]) * sizeof(fBuffer2[0]));

     sum0 = sum1 = sum2 = 0;

     uint8_t* dstCursor = dstEnd;
     const uint8_t* srcCursor = srcEnd;
     do {
         dstCursor -= dstStride;
         srcCursor -= srcStride;
         uint32_t s = *srcCursor;
         sum0 += s;
         sum1 += sum0;
         sum2 += sum1;

         *dstCursor = SkTo<uint8_t>((info.scaledWeight() * sum2 + half) >> 32);

         sum2 -= *buffer2Cursor;
         *buffer2Cursor = sum1;
         buffer2Cursor = (buffer2Cursor + 1) < buffer2End ? buffer2Cursor + 1 : &fBuffer2[0];

         sum1 -= *buffer1Cursor;
         *buffer1Cursor = sum0;
         buffer1Cursor = (buffer1Cursor + 1) < buffer1End ? buffer1Cursor + 1 : &fBuffer1[0];

         sum0 -= *buffer0Cursor;
         *buffer0Cursor = s;
         buffer0Cursor = (buffer0Cursor + 1) < buffer0End ? buffer0Cursor + 1 : &fBuffer0[0];
     } while (dstCursor > dst);
 }
	/*
	* Copyright 2017 Google Inc.
	*
	* Use of this source code is governed by a BSD-style license that can be
	* found in the LICENSE file.
	*/

	#include "SkMaskBlurFilter.h"

	#include <cmath>

	#include "SkMakeUnique.h"

	static const double kPi = 3.14159265358979323846264338327950288;

	static uint64_t weight_from_diameter(uint32_t d) {
	uint64_t d2 = d * d;
	uint64_t d3 = d2 * d;
	if ((d&1) == 0) {
	// d * d * (d + 1);
	return d3 + d2;
	}

	return d3;
	}

	static uint32_t filter_window(double sigma) {
	auto possibleWindow = static_cast<uint32_t>(floor(sigma * 3 * sqrt(2*kPi)/4 + 0.5));
	return std::max(1u, possibleWindow);
	}

	SkMaskBlurFilter::FilterInfo::FilterInfo(double sigma)
	: fFilterWindow{filter_window(sigma)}
	, fScaledWeight{(static_cast<uint64_t>(1) << 32) / weight_from_diameter(fFilterWindow)} {}

	uint64_t SkMaskBlurFilter::FilterInfo::weight() const {
	return weight_from_diameter(fFilterWindow);

	}
	uint32_t SkMaskBlurFilter::FilterInfo::borderSize() const {
	if ((fFilterWindow&1) == 0) {
	return 3 * (fFilterWindow / 2) - 1;
	}
	return 3 * (fFilterWindow / 2);
	}

	size_t SkMaskBlurFilter::FilterInfo::diameter(uint8_t pass) const {
	SkASSERT(pass <= 2);

	if ((fFilterWindow&1) == 0) {
	// Handle even case.
	switch (pass) {
	case 0: return fFilterWindow;
	case 1: return fFilterWindow;
	case 2: return fFilterWindow+1;
	}
	}

	return fFilterWindow;
	}

	uint64_t SkMaskBlurFilter::FilterInfo::scaledWeight() const {
	return fScaledWeight;
	}

	SkMaskBlurFilter::SkMaskBlurFilter(double sigmaW, double sigmaH)
	: fInfoW{sigmaW}, fInfoH{sigmaH}
	, fBuffer0{skstd::make_unique_default<uint32_t[]>(bufferSize(0))}
	, fBuffer1{skstd::make_unique_default<uint32_t[]>(bufferSize(1))}
	, fBuffer2{skstd::make_unique_default<uint32_t[]>(bufferSize(2))} {
	}

	SkIPoint SkMaskBlurFilter::blur(const SkMask& src, SkMask* dst) const {

	uint64_t weightW = fInfoW.weight();
	uint64_t weightH = fInfoH.weight();

	size_t borderW = fInfoW.borderSize();
	size_t borderH = fInfoH.borderSize();

	size_t srcW = src.fBounds.width();
	size_t srcH = src.fBounds.height();

	size_t dstW = srcW + 2 * borderW;
	size_t dstH = srcH + 2 * borderH;

	dst->fBounds.set(0, 0, dstW, dstH);
	dst->fBounds.offset(src.fBounds.x(), src.fBounds.y());
	dst->fBounds.offset(-SkTo<int32_t>(borderW), -SkTo<int32_t>(borderH));

	dst->fImage = nullptr;
	dst->fRowBytes = dstW;
	dst->fFormat = SkMask::kA8_Format;

	if (src.fImage == nullptr) {
	return {SkTo<int32_t>(borderW), SkTo<int32_t>(borderH)};
	}

	dst->fImage = SkMask::AllocImage(dstW * dstH);

	if (weightW > 1 && weightH > 1) {
	// Blur both directions.
	size_t tmpW = srcH;
	size_t tmpH = dstW;
	auto tmp = skstd::make_unique_default<uint8_t[]>(tmpW * tmpH);

	// Blur horizontally, and transpose.
	for (size_t y = 0; y < srcH; y++) {
	auto srcStart = &src.fImage[y * src.fRowBytes];
	auto tmpStart = &tmp[y];
	this->blurOneScan(fInfoW,
	srcStart, 1, srcStart + srcW,
	tmpStart, tmpW, tmpStart + tmpW * tmpH);
	}

	// Blur vertically (scan in memory order because of the transposition),
	// and transpose back to the original orientation.
	for (size_t y = 0; y < tmpH; y++) {
	auto tmpStart = &tmp[y * tmpW];
	auto dstStart = &dst->fImage[y];
	this->blurOneScan(fInfoH,
	tmpStart, 1, tmpStart + tmpW,
	dstStart, dst->fRowBytes, dstStart + dst->fRowBytes * dstH);
	}
	} else if (weightW > 1) {
	// Blur only horizontally.

	for (size_t y = 0; y < srcH; y++) {
	auto srcStart = &src.fImage[y * src.fRowBytes];
	auto dstStart = &dst->fImage[y * dst->fRowBytes];
	this->blurOneScan(fInfoW,
	srcStart, 1, srcStart + srcW,
	dstStart, 1, dstStart + dstW);
	}
	} else if (weightH > 1) {
	// Blur only vertically.

	for (size_t x = 0; x < srcW; x++) {
	auto srcStart = &src.fImage[x];
	auto srcEnd = &src.fImage[src.fRowBytes * srcH];
	auto dstStart = &dst->fImage[x];
	auto dstEnd = &dst->fImage[dst->fRowBytes * dstH];
	this->blurOneScan(fInfoH,
	srcStart, src.fRowBytes, srcEnd,
	dstStart, dst->fRowBytes, dstEnd);
	}
	} else {
	// Copy to dst. No Blur.

	for (size_t y = 0; y < srcH; y++) {
	std::memcpy(&dst->fImage[y * dst->fRowBytes], &src.fImage[y * src.fRowBytes], dstW);
	}
	}

	return {SkTo<int32_t>(borderW), SkTo<int32_t>(borderH)};
	}

	size_t SkMaskBlurFilter::bufferSize(uint8_t bufferPass) const {
	return std::max(fInfoW.diameter(bufferPass), fInfoH.diameter(bufferPass)) - 1;
	}

	// Blur one horizontal scan into the dst.
	void SkMaskBlurFilter::blurOneScan(
	FilterInfo info,
	const uint8_t* src, size_t srcStride, const uint8_t* srcEnd,
	uint8_t* dst, size_t dstStride, uint8_t* dstEnd) const {

	auto buffer0Begin = &fBuffer0[0];
	auto buffer1Begin = &fBuffer1[0];
	auto buffer2Begin = &fBuffer2[0];

	auto buffer0Cursor = buffer0Begin;
	auto buffer1Cursor = buffer1Begin;
	auto buffer2Cursor = buffer2Begin;

	auto buffer0End = &fBuffer0[0] + info.diameter(0) - 1;
	auto buffer1End = &fBuffer1[0] + info.diameter(1) - 1;
	auto buffer2End = &fBuffer2[0] + info.diameter(2) - 1;

	std::memset(&fBuffer0[0], 0, (buffer0End - buffer0Begin) * sizeof(fBuffer0[0]));
	std::memset(&fBuffer1[0], 0, (buffer1End - buffer1Begin) * sizeof(fBuffer1[0]));
	std::memset(&fBuffer2[0], 0, (buffer2End - buffer2Begin) * sizeof(fBuffer2[0]));

	uint32_t sum0 = 0;
	uint32_t sum1 = 0;
	uint32_t sum2 = 0;

	const uint64_t half = static_cast<uint64_t>(1) << 31;

	// Consume the source generating pixels.
	for (auto srcCursor = src; srcCursor < srcEnd; dst += dstStride, srcCursor += srcStride) {
	uint32_t s = *srcCursor;
	sum0 += s;
	sum1 += sum0;
	sum2 += sum1;

	dst = SkTo<uint8_t>((info.scaledWeight() sum2 + half) >> 32);

	sum2 -= *buffer2Cursor;
	*buffer2Cursor = sum1;
	buffer2Cursor = (buffer2Cursor + 1) < buffer2End ? buffer2Cursor + 1 : &fBuffer2[0];

	sum1 -= *buffer1Cursor;
	*buffer1Cursor = sum0;
	buffer1Cursor = (buffer1Cursor + 1) < buffer1End ? buffer1Cursor + 1 : &fBuffer1[0];

	sum0 -= *buffer0Cursor;
	*buffer0Cursor = s;
	buffer0Cursor = (buffer0Cursor + 1) < buffer0End ? buffer0Cursor + 1 : &fBuffer0[0];
	}

	// This handles the case when both ends of the box are not between [src, srcEnd), and both
	// are zero at that point.
	for (auto i = 0; i < static_cast<ptrdiff_t>(2 * info.borderSize()) - (srcEnd - src); i++) {
	uint32_t s = 0;
	sum0 += s;
	sum1 += sum0;
	sum2 += sum1;

	dst = SkTo<uint8_t>((info.scaledWeight() sum2 + half) >> 32);

	sum2 -= *buffer2Cursor;
	*buffer2Cursor = sum1;
	buffer2Cursor = (buffer2Cursor + 1) < buffer2End ? buffer2Cursor + 1 : &fBuffer2[0];

	sum1 -= *buffer1Cursor;
	*buffer1Cursor = sum0;
	buffer1Cursor = (buffer1Cursor + 1) < buffer1End ? buffer1Cursor + 1 : &fBuffer1[0];

	sum0 -= *buffer0Cursor;
	*buffer0Cursor = s;
	buffer0Cursor = (buffer0Cursor + 1) < buffer0End ? buffer0Cursor + 1 : &fBuffer0[0];
	dst += dstStride;
	}

	// Starting from the right, fill in the rest of the buffer.
	std::memset(&fBuffer0[0], 0, (buffer0End - &fBuffer0[0]) * sizeof(fBuffer0[0]));
	std::memset(&fBuffer1[0], 0, (buffer1End - &fBuffer1[0]) * sizeof(fBuffer1[0]));
	std::memset(&fBuffer2[0], 0, (buffer2End - &fBuffer2[0]) * sizeof(fBuffer2[0]));

	sum0 = sum1 = sum2 = 0;

	uint8_t* dstCursor = dstEnd;
	const uint8_t* srcCursor = srcEnd;
	do {
	dstCursor -= dstStride;
	srcCursor -= srcStride;
	uint32_t s = *srcCursor;
	sum0 += s;
	sum1 += sum0;
	sum2 += sum1;

	dstCursor = SkTo<uint8_t>((info.scaledWeight() sum2 + half) >> 32);

	sum2 -= *buffer2Cursor;
	*buffer2Cursor = sum1;
	buffer2Cursor = (buffer2Cursor + 1) < buffer2End ? buffer2Cursor + 1 : &fBuffer2[0];

	sum1 -= *buffer1Cursor;
	*buffer1Cursor = sum0;
	buffer1Cursor = (buffer1Cursor + 1) < buffer1End ? buffer1Cursor + 1 : &fBuffer1[0];

	sum0 -= *buffer0Cursor;
	*buffer0Cursor = s;
	buffer0Cursor = (buffer0Cursor + 1) < buffer0End ? buffer0Cursor + 1 : &fBuffer0[0];
	} while (dstCursor > dst);
	}