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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-19 00:47:55 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-19 00:47:55 +0000
commit26a029d407be480d791972afb5975cf62c9360a6 (patch)
treef435a8308119effd964b339f76abb83a57c29483 /gfx/2d/SkConvolver.cpp
parentInitial commit. (diff)
downloadfirefox-26a029d407be480d791972afb5975cf62c9360a6.tar.xz
firefox-26a029d407be480d791972afb5975cf62c9360a6.zip
Adding upstream version 124.0.1.upstream/124.0.1
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'gfx/2d/SkConvolver.cpp')
-rw-r--r--gfx/2d/SkConvolver.cpp559
1 files changed, 559 insertions, 0 deletions
diff --git a/gfx/2d/SkConvolver.cpp b/gfx/2d/SkConvolver.cpp
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+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+// Copyright (c) 2011-2016 Google Inc.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the gfx/skia/LICENSE file.
+
+#include "SkConvolver.h"
+#include "mozilla/Vector.h"
+
+#ifdef USE_SSE2
+# include "mozilla/SSE.h"
+#endif
+
+#ifdef USE_NEON
+# include "mozilla/arm.h"
+#endif
+
+namespace skia {
+
+// Converts the argument to an 8-bit unsigned value by clamping to the range
+// 0-255.
+static inline unsigned char ClampTo8(int a) {
+ if (static_cast<unsigned>(a) < 256) {
+ return a; // Avoid the extra check in the common case.
+ }
+ if (a < 0) {
+ return 0;
+ }
+ return 255;
+}
+
+// Convolves horizontally along a single row. The row data is given in
+// |srcData| and continues for the numValues() of the filter.
+template <bool hasAlpha>
+void ConvolveHorizontally(const unsigned char* srcData,
+ const SkConvolutionFilter1D& filter,
+ unsigned char* outRow) {
+ // Loop over each pixel on this row in the output image.
+ int numValues = filter.numValues();
+ for (int outX = 0; outX < numValues; outX++) {
+ // Get the filter that determines the current output pixel.
+ int filterOffset, filterLength;
+ const SkConvolutionFilter1D::ConvolutionFixed* filterValues =
+ filter.FilterForValue(outX, &filterOffset, &filterLength);
+
+ // Compute the first pixel in this row that the filter affects. It will
+ // touch |filterLength| pixels (4 bytes each) after this.
+ const unsigned char* rowToFilter = &srcData[filterOffset * 4];
+
+ // Apply the filter to the row to get the destination pixel in |accum|.
+ int accum[4] = {0};
+ for (int filterX = 0; filterX < filterLength; filterX++) {
+ SkConvolutionFilter1D::ConvolutionFixed curFilter = filterValues[filterX];
+ accum[0] += curFilter * rowToFilter[filterX * 4 + 0];
+ accum[1] += curFilter * rowToFilter[filterX * 4 + 1];
+ accum[2] += curFilter * rowToFilter[filterX * 4 + 2];
+ if (hasAlpha) {
+ accum[3] += curFilter * rowToFilter[filterX * 4 + 3];
+ }
+ }
+
+ // Bring this value back in range. All of the filter scaling factors
+ // are in fixed point with kShiftBits bits of fractional part.
+ accum[0] >>= SkConvolutionFilter1D::kShiftBits;
+ accum[1] >>= SkConvolutionFilter1D::kShiftBits;
+ accum[2] >>= SkConvolutionFilter1D::kShiftBits;
+
+ if (hasAlpha) {
+ accum[3] >>= SkConvolutionFilter1D::kShiftBits;
+ }
+
+ // Store the new pixel.
+ outRow[outX * 4 + 0] = ClampTo8(accum[0]);
+ outRow[outX * 4 + 1] = ClampTo8(accum[1]);
+ outRow[outX * 4 + 2] = ClampTo8(accum[2]);
+ if (hasAlpha) {
+ outRow[outX * 4 + 3] = ClampTo8(accum[3]);
+ }
+ }
+}
+
+// Does vertical convolution to produce one output row. The filter values and
+// length are given in the first two parameters. These are applied to each
+// of the rows pointed to in the |sourceDataRows| array, with each row
+// being |pixelWidth| wide.
+//
+// The output must have room for |pixelWidth * 4| bytes.
+template <bool hasAlpha>
+void ConvolveVertically(
+ const SkConvolutionFilter1D::ConvolutionFixed* filterValues,
+ int filterLength, unsigned char* const* sourceDataRows, int pixelWidth,
+ unsigned char* outRow) {
+ // We go through each column in the output and do a vertical convolution,
+ // generating one output pixel each time.
+ for (int outX = 0; outX < pixelWidth; outX++) {
+ // Compute the number of bytes over in each row that the current column
+ // we're convolving starts at. The pixel will cover the next 4 bytes.
+ int byteOffset = outX * 4;
+
+ // Apply the filter to one column of pixels.
+ int accum[4] = {0};
+ for (int filterY = 0; filterY < filterLength; filterY++) {
+ SkConvolutionFilter1D::ConvolutionFixed curFilter = filterValues[filterY];
+ accum[0] += curFilter * sourceDataRows[filterY][byteOffset + 0];
+ accum[1] += curFilter * sourceDataRows[filterY][byteOffset + 1];
+ accum[2] += curFilter * sourceDataRows[filterY][byteOffset + 2];
+ if (hasAlpha) {
+ accum[3] += curFilter * sourceDataRows[filterY][byteOffset + 3];
+ }
+ }
+
+ // Bring this value back in range. All of the filter scaling factors
+ // are in fixed point with kShiftBits bits of precision.
+ accum[0] >>= SkConvolutionFilter1D::kShiftBits;
+ accum[1] >>= SkConvolutionFilter1D::kShiftBits;
+ accum[2] >>= SkConvolutionFilter1D::kShiftBits;
+ if (hasAlpha) {
+ accum[3] >>= SkConvolutionFilter1D::kShiftBits;
+ }
+
+ // Store the new pixel.
+ outRow[byteOffset + 0] = ClampTo8(accum[0]);
+ outRow[byteOffset + 1] = ClampTo8(accum[1]);
+ outRow[byteOffset + 2] = ClampTo8(accum[2]);
+
+ if (hasAlpha) {
+ unsigned char alpha = ClampTo8(accum[3]);
+
+ // Make sure the alpha channel doesn't come out smaller than any of the
+ // color channels. We use premultipled alpha channels, so this should
+ // never happen, but rounding errors will cause this from time to time.
+ // These "impossible" colors will cause overflows (and hence random pixel
+ // values) when the resulting bitmap is drawn to the screen.
+ //
+ // We only need to do this when generating the final output row (here).
+ int maxColorChannel =
+ std::max(outRow[byteOffset + 0],
+ std::max(outRow[byteOffset + 1], outRow[byteOffset + 2]));
+ if (alpha < maxColorChannel) {
+ outRow[byteOffset + 3] = maxColorChannel;
+ } else {
+ outRow[byteOffset + 3] = alpha;
+ }
+ } else {
+ // No alpha channel, the image is opaque.
+ outRow[byteOffset + 3] = 0xff;
+ }
+ }
+}
+
+#ifdef USE_SSE2
+void convolve_vertically_avx2(const int16_t* filter, int filterLen,
+ uint8_t* const* srcRows, int width, uint8_t* out,
+ bool hasAlpha);
+void convolve_horizontally_sse2(const unsigned char* srcData,
+ const SkConvolutionFilter1D& filter,
+ unsigned char* outRow, bool hasAlpha);
+void convolve_vertically_sse2(const int16_t* filter, int filterLen,
+ uint8_t* const* srcRows, int width, uint8_t* out,
+ bool hasAlpha);
+#elif defined(USE_NEON)
+void convolve_horizontally_neon(const unsigned char* srcData,
+ const SkConvolutionFilter1D& filter,
+ unsigned char* outRow, bool hasAlpha);
+void convolve_vertically_neon(const int16_t* filter, int filterLen,
+ uint8_t* const* srcRows, int width, uint8_t* out,
+ bool hasAlpha);
+#endif
+
+void convolve_horizontally(const unsigned char* srcData,
+ const SkConvolutionFilter1D& filter,
+ unsigned char* outRow, bool hasAlpha) {
+#ifdef USE_SSE2
+ if (mozilla::supports_sse2()) {
+ convolve_horizontally_sse2(srcData, filter, outRow, hasAlpha);
+ return;
+ }
+#elif defined(USE_NEON)
+ if (mozilla::supports_neon()) {
+ convolve_horizontally_neon(srcData, filter, outRow, hasAlpha);
+ return;
+ }
+#endif
+ if (hasAlpha) {
+ ConvolveHorizontally<true>(srcData, filter, outRow);
+ } else {
+ ConvolveHorizontally<false>(srcData, filter, outRow);
+ }
+}
+
+void convolve_vertically(
+ const SkConvolutionFilter1D::ConvolutionFixed* filterValues,
+ int filterLength, unsigned char* const* sourceDataRows, int pixelWidth,
+ unsigned char* outRow, bool hasAlpha) {
+#ifdef USE_SSE2
+ if (mozilla::supports_avx2()) {
+ convolve_vertically_avx2(filterValues, filterLength, sourceDataRows,
+ pixelWidth, outRow, hasAlpha);
+ return;
+ }
+ if (mozilla::supports_sse2()) {
+ convolve_vertically_sse2(filterValues, filterLength, sourceDataRows,
+ pixelWidth, outRow, hasAlpha);
+ return;
+ }
+#elif defined(USE_NEON)
+ if (mozilla::supports_neon()) {
+ convolve_vertically_neon(filterValues, filterLength, sourceDataRows,
+ pixelWidth, outRow, hasAlpha);
+ return;
+ }
+#endif
+ if (hasAlpha) {
+ ConvolveVertically<true>(filterValues, filterLength, sourceDataRows,
+ pixelWidth, outRow);
+ } else {
+ ConvolveVertically<false>(filterValues, filterLength, sourceDataRows,
+ pixelWidth, outRow);
+ }
+}
+
+// Stores a list of rows in a circular buffer. The usage is you write into it
+// by calling AdvanceRow. It will keep track of which row in the buffer it
+// should use next, and the total number of rows added.
+class CircularRowBuffer {
+ public:
+ // The number of pixels in each row is given in |sourceRowPixelWidth|.
+ // The maximum number of rows needed in the buffer is |maxYFilterSize|
+ // (we only need to store enough rows for the biggest filter).
+ //
+ // We use the |firstInputRow| to compute the coordinates of all of the
+ // following rows returned by Advance().
+ CircularRowBuffer(int destRowPixelWidth, int maxYFilterSize,
+ int firstInputRow)
+ : fRowByteWidth(destRowPixelWidth * 4),
+ fNumRows(maxYFilterSize),
+ fNextRow(0),
+ fNextRowCoordinate(firstInputRow) {
+ fBuffer.resize(fRowByteWidth * maxYFilterSize);
+ fRowAddresses.resize(fNumRows);
+ }
+
+ // Moves to the next row in the buffer, returning a pointer to the beginning
+ // of it.
+ unsigned char* advanceRow() {
+ unsigned char* row = &fBuffer[fNextRow * fRowByteWidth];
+ fNextRowCoordinate++;
+
+ // Set the pointer to the next row to use, wrapping around if necessary.
+ fNextRow++;
+ if (fNextRow == fNumRows) {
+ fNextRow = 0;
+ }
+ return row;
+ }
+
+ // Returns a pointer to an "unrolled" array of rows. These rows will start
+ // at the y coordinate placed into |*firstRowIndex| and will continue in
+ // order for the maximum number of rows in this circular buffer.
+ //
+ // The |firstRowIndex_| may be negative. This means the circular buffer
+ // starts before the top of the image (it hasn't been filled yet).
+ unsigned char* const* GetRowAddresses(int* firstRowIndex) {
+ // Example for a 4-element circular buffer holding coords 6-9.
+ // Row 0 Coord 8
+ // Row 1 Coord 9
+ // Row 2 Coord 6 <- fNextRow = 2, fNextRowCoordinate = 10.
+ // Row 3 Coord 7
+ //
+ // The "next" row is also the first (lowest) coordinate. This computation
+ // may yield a negative value, but that's OK, the math will work out
+ // since the user of this buffer will compute the offset relative
+ // to the firstRowIndex and the negative rows will never be used.
+ *firstRowIndex = fNextRowCoordinate - fNumRows;
+
+ int curRow = fNextRow;
+ for (int i = 0; i < fNumRows; i++) {
+ fRowAddresses[i] = &fBuffer[curRow * fRowByteWidth];
+
+ // Advance to the next row, wrapping if necessary.
+ curRow++;
+ if (curRow == fNumRows) {
+ curRow = 0;
+ }
+ }
+ return &fRowAddresses[0];
+ }
+
+ private:
+ // The buffer storing the rows. They are packed, each one fRowByteWidth.
+ std::vector<unsigned char> fBuffer;
+
+ // Number of bytes per row in the |buffer|.
+ int fRowByteWidth;
+
+ // The number of rows available in the buffer.
+ int fNumRows;
+
+ // The next row index we should write into. This wraps around as the
+ // circular buffer is used.
+ int fNextRow;
+
+ // The y coordinate of the |fNextRow|. This is incremented each time a
+ // new row is appended and does not wrap.
+ int fNextRowCoordinate;
+
+ // Buffer used by GetRowAddresses().
+ std::vector<unsigned char*> fRowAddresses;
+};
+
+SkConvolutionFilter1D::SkConvolutionFilter1D() : fMaxFilter(0) {}
+
+SkConvolutionFilter1D::~SkConvolutionFilter1D() = default;
+
+void SkConvolutionFilter1D::AddFilter(int filterOffset,
+ const ConvolutionFixed* filterValues,
+ int filterLength) {
+ // It is common for leading/trailing filter values to be zeros. In such
+ // cases it is beneficial to only store the central factors.
+ // For a scaling to 1/4th in each dimension using a Lanczos-2 filter on
+ // a 1080p image this optimization gives a ~10% speed improvement.
+ int filterSize = filterLength;
+ int firstNonZero = 0;
+ while (firstNonZero < filterLength && filterValues[firstNonZero] == 0) {
+ firstNonZero++;
+ }
+
+ if (firstNonZero < filterLength) {
+ // Here we have at least one non-zero factor.
+ int lastNonZero = filterLength - 1;
+ while (lastNonZero >= 0 && filterValues[lastNonZero] == 0) {
+ lastNonZero--;
+ }
+
+ filterOffset += firstNonZero;
+ filterLength = lastNonZero + 1 - firstNonZero;
+ MOZ_ASSERT(filterLength > 0);
+
+ fFilterValues.insert(fFilterValues.end(), &filterValues[firstNonZero],
+ &filterValues[lastNonZero + 1]);
+ } else {
+ // Here all the factors were zeroes.
+ filterLength = 0;
+ }
+
+ FilterInstance instance = {
+ // We pushed filterLength elements onto fFilterValues
+ int(fFilterValues.size()) - filterLength, filterOffset, filterLength,
+ filterSize};
+ fFilters.push_back(instance);
+
+ fMaxFilter = std::max(fMaxFilter, filterLength);
+}
+
+bool SkConvolutionFilter1D::ComputeFilterValues(
+ const SkBitmapFilter& aBitmapFilter, int32_t aSrcSize, int32_t aDstSize) {
+ // When we're doing a magnification, the scale will be larger than one. This
+ // means the destination pixels are much smaller than the source pixels, and
+ // that the range covered by the filter won't necessarily cover any source
+ // pixel boundaries. Therefore, we use these clamped values (max of 1) for
+ // some computations.
+ float scale = float(aDstSize) / float(aSrcSize);
+ float clampedScale = std::min(1.0f, scale);
+ // This is how many source pixels from the center we need to count
+ // to support the filtering function.
+ float srcSupport = aBitmapFilter.width() / clampedScale;
+ float invScale = 1.0f / scale;
+
+ mozilla::Vector<float, 64> filterValues;
+ mozilla::Vector<ConvolutionFixed, 64> fixedFilterValues;
+
+ // Loop over all pixels in the output range. We will generate one set of
+ // filter values for each one. Those values will tell us how to blend the
+ // source pixels to compute the destination pixel.
+
+ // This value is computed based on how SkTDArray::resizeStorageToAtLeast works
+ // in order to ensure that it does not overflow or assert. That functions
+ // computes
+ // n+4 + (n+4)/4
+ // and we want to to fit in a 32 bit signed int. Equating that to 2^31-1 and
+ // solving n gives n = (2^31-6)*4/5 = 1717986913.6
+ const int32_t maxToPassToReserveAdditional = 1717986913;
+
+ int32_t filterValueCount = int32_t(ceilf(aDstSize * srcSupport * 2));
+ if (aDstSize > maxToPassToReserveAdditional || filterValueCount < 0 ||
+ filterValueCount > maxToPassToReserveAdditional) {
+ return false;
+ }
+ reserveAdditional(aDstSize, filterValueCount);
+ for (int32_t destI = 0; destI < aDstSize; destI++) {
+ // This is the pixel in the source directly under the pixel in the dest.
+ // Note that we base computations on the "center" of the pixels. To see
+ // why, observe that the destination pixel at coordinates (0, 0) in a 5.0x
+ // downscale should "cover" the pixels around the pixel with *its center*
+ // at coordinates (2.5, 2.5) in the source, not those around (0, 0).
+ // Hence we need to scale coordinates (0.5, 0.5), not (0, 0).
+ float srcPixel = (static_cast<float>(destI) + 0.5f) * invScale;
+
+ // Compute the (inclusive) range of source pixels the filter covers.
+ float srcBegin = std::max(0.0f, floorf(srcPixel - srcSupport));
+ float srcEnd = std::min(aSrcSize - 1.0f, ceilf(srcPixel + srcSupport));
+
+ // Compute the unnormalized filter value at each location of the source
+ // it covers.
+
+ // Sum of the filter values for normalizing.
+ // Distance from the center of the filter, this is the filter coordinate
+ // in source space. We also need to consider the center of the pixel
+ // when comparing distance against 'srcPixel'. In the 5x downscale
+ // example used above the distance from the center of the filter to
+ // the pixel with coordinates (2, 2) should be 0, because its center
+ // is at (2.5, 2.5).
+ int32_t filterCount = int32_t(srcEnd - srcBegin) + 1;
+ if (filterCount <= 0 || !filterValues.resize(filterCount) ||
+ !fixedFilterValues.resize(filterCount)) {
+ return false;
+ }
+
+ float destFilterDist = (srcBegin + 0.5f - srcPixel) * clampedScale;
+ float filterSum = 0.0f;
+ for (int32_t index = 0; index < filterCount; index++) {
+ float filterValue = aBitmapFilter.evaluate(destFilterDist);
+ filterValues[index] = filterValue;
+ filterSum += filterValue;
+ destFilterDist += clampedScale;
+ }
+
+ // The filter must be normalized so that we don't affect the brightness of
+ // the image. Convert to normalized fixed point.
+ ConvolutionFixed fixedSum = 0;
+ float invFilterSum = 1.0f / filterSum;
+ for (int32_t fixedI = 0; fixedI < filterCount; fixedI++) {
+ ConvolutionFixed curFixed = ToFixed(filterValues[fixedI] * invFilterSum);
+ fixedSum += curFixed;
+ fixedFilterValues[fixedI] = curFixed;
+ }
+
+ // The conversion to fixed point will leave some rounding errors, which
+ // we add back in to avoid affecting the brightness of the image. We
+ // arbitrarily add this to the center of the filter array (this won't always
+ // be the center of the filter function since it could get clipped on the
+ // edges, but it doesn't matter enough to worry about that case).
+ ConvolutionFixed leftovers = ToFixed(1) - fixedSum;
+ fixedFilterValues[filterCount / 2] += leftovers;
+
+ AddFilter(int32_t(srcBegin), fixedFilterValues.begin(), filterCount);
+ }
+
+ return maxFilter() > 0 && numValues() == aDstSize;
+}
+
+// Does a two-dimensional convolution on the given source image.
+//
+// It is assumed the source pixel offsets referenced in the input filters
+// reference only valid pixels, so the source image size is not required. Each
+// row of the source image starts |sourceByteRowStride| after the previous
+// one (this allows you to have rows with some padding at the end).
+//
+// The result will be put into the given output buffer. The destination image
+// size will be xfilter.numValues() * yfilter.numValues() pixels. It will be
+// in rows of exactly xfilter.numValues() * 4 bytes.
+//
+// |sourceHasAlpha| is a hint that allows us to avoid doing computations on
+// the alpha channel if the image is opaque. If you don't know, set this to
+// true and it will work properly, but setting this to false will be a few
+// percent faster if you know the image is opaque.
+//
+// The layout in memory is assumed to be 4-bytes per pixel in B-G-R-A order
+// (this is ARGB when loaded into 32-bit words on a little-endian machine).
+/**
+ * Returns false if it was unable to perform the convolution/rescale. in which
+ * case the output buffer is assumed to be undefined.
+ */
+bool BGRAConvolve2D(const unsigned char* sourceData, int sourceByteRowStride,
+ bool sourceHasAlpha, const SkConvolutionFilter1D& filterX,
+ const SkConvolutionFilter1D& filterY,
+ int outputByteRowStride, unsigned char* output) {
+ int maxYFilterSize = filterY.maxFilter();
+
+ // The next row in the input that we will generate a horizontally
+ // convolved row for. If the filter doesn't start at the beginning of the
+ // image (this is the case when we are only resizing a subset), then we
+ // don't want to generate any output rows before that. Compute the starting
+ // row for convolution as the first pixel for the first vertical filter.
+ int filterOffset = 0, filterLength = 0;
+ const SkConvolutionFilter1D::ConvolutionFixed* filterValues =
+ filterY.FilterForValue(0, &filterOffset, &filterLength);
+ int nextXRow = filterOffset;
+
+ // We loop over each row in the input doing a horizontal convolution. This
+ // will result in a horizontally convolved image. We write the results into
+ // a circular buffer of convolved rows and do vertical convolution as rows
+ // are available. This prevents us from having to store the entire
+ // intermediate image and helps cache coherency.
+ // We will need four extra rows to allow horizontal convolution could be done
+ // simultaneously. We also pad each row in row buffer to be aligned-up to
+ // 32 bytes.
+ // TODO(jiesun): We do not use aligned load from row buffer in vertical
+ // convolution pass yet. Somehow Windows does not like it.
+ int rowBufferWidth = (filterX.numValues() + 31) & ~0x1F;
+ int rowBufferHeight = maxYFilterSize;
+
+ // check for too-big allocation requests : crbug.com/528628
+ {
+ int64_t size = int64_t(rowBufferWidth) * int64_t(rowBufferHeight);
+ // need some limit, to avoid over-committing success from malloc, but then
+ // crashing when we try to actually use the memory.
+ // 100meg seems big enough to allow "normal" zoom factors and image sizes
+ // through while avoiding the crash seen by the bug (crbug.com/528628)
+ if (size > 100 * 1024 * 1024) {
+ // printf_stderr("BGRAConvolve2D: tmp allocation [%lld] too
+ // big\n", size);
+ return false;
+ }
+ }
+
+ CircularRowBuffer rowBuffer(rowBufferWidth, rowBufferHeight, filterOffset);
+
+ // Loop over every possible output row, processing just enough horizontal
+ // convolutions to run each subsequent vertical convolution.
+ MOZ_ASSERT(outputByteRowStride >= filterX.numValues() * 4);
+ int numOutputRows = filterY.numValues();
+
+ // We need to check which is the last line to convolve before we advance 4
+ // lines in one iteration.
+ int lastFilterOffset, lastFilterLength;
+ filterY.FilterForValue(numOutputRows - 1, &lastFilterOffset,
+ &lastFilterLength);
+
+ for (int outY = 0; outY < numOutputRows; outY++) {
+ filterValues = filterY.FilterForValue(outY, &filterOffset, &filterLength);
+
+ // Generate output rows until we have enough to run the current filter.
+ while (nextXRow < filterOffset + filterLength) {
+ convolve_horizontally(
+ &sourceData[(uint64_t)nextXRow * sourceByteRowStride], filterX,
+ rowBuffer.advanceRow(), sourceHasAlpha);
+ nextXRow++;
+ }
+
+ // Compute where in the output image this row of final data will go.
+ unsigned char* curOutputRow = &output[(uint64_t)outY * outputByteRowStride];
+
+ // Get the list of rows that the circular buffer has, in order.
+ int firstRowInCircularBuffer;
+ unsigned char* const* rowsToConvolve =
+ rowBuffer.GetRowAddresses(&firstRowInCircularBuffer);
+
+ // Now compute the start of the subset of those rows that the filter needs.
+ unsigned char* const* firstRowForFilter =
+ &rowsToConvolve[filterOffset - firstRowInCircularBuffer];
+
+ convolve_vertically(filterValues, filterLength, firstRowForFilter,
+ filterX.numValues(), curOutputRow, sourceHasAlpha);
+ }
+ return true;
+}
+
+} // namespace skia