The Tor Browser: gfx/skia/trunk/src/core/SkConvolver.cpp@6474c204b198 (annotated)

gfx/skia/trunk/src/core/SkConvolver.cpp@6474c204b198 (annotated)

gfx/skia/trunk/src/core/SkConvolver.cpp

Wed, 31 Dec 2014 06:09:35 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Wed, 31 Dec 2014 06:09:35 +0100
changeset 0: 6474c204b198
permissions: -rw-r--r--

Cloned upstream origin tor-browser at tor-browser-31.3.0esr-4.5-1-build1
revision ID fc1c9ff7c1b2defdbc039f12214767608f46423f for hacking purpose.

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 #include "SkConvolver.h"
 #include "SkSize.h"
 #include "SkTypes.h"
 namespace {
     // Converts the argument to an 8-bit unsigned value by clamping to the range
     // 0-255.
     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;
     }
     // 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.reset(fRowByteWidth * maxYFilterSize);
             fRowAddresses.reset(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.
         SkTArray<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().
         SkTArray<unsigned char*> fRowAddresses;
     };
 // 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 = SkTMax(outRow[byteOffset + 0],
                                                SkTMax(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;
             }
         }
     }
     void ConvolveVertically(const SkConvolutionFilter1D::ConvolutionFixed* filterValues,
                             int filterLength,
                             unsigned char* const* sourceDataRows,
                             int pixelWidth,
                             unsigned char* outRow,
                             bool sourceHasAlpha) {
         if (sourceHasAlpha) {
             ConvolveVertically<true>(filterValues, filterLength,
                                      sourceDataRows, pixelWidth,
                                      outRow);
         } else {
             ConvolveVertically<false>(filterValues, filterLength,
                                       sourceDataRows, pixelWidth,
                                       outRow);
         }
     }
 }  // namespace
 // SkConvolutionFilter1D ---------------------------------------------------------
 SkConvolutionFilter1D::SkConvolutionFilter1D()
 : fMaxFilter(0) {
 }
 SkConvolutionFilter1D::~SkConvolutionFilter1D() {
 }
 void SkConvolutionFilter1D::AddFilter(int filterOffset,
                                       const float* filterValues,
                                       int filterLength) {
     SkASSERT(filterLength > 0);
     SkTArray<ConvolutionFixed> fixedValues;
     fixedValues.reset(filterLength);
     for (int i = 0; i < filterLength; ++i) {
         fixedValues.push_back(FloatToFixed(filterValues[i]));
     }
     AddFilter(filterOffset, &fixedValues[0], filterLength);
 }
 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;
         SkASSERT(filterLength > 0);
         for (int i = firstNonZero; i <= lastNonZero; i++) {
             fFilterValues.push_back(filterValues[i]);
         }
     } else {
         // Here all the factors were zeroes.
         filterLength = 0;
     }
     FilterInstance instance;
     // We pushed filterLength elements onto fFilterValues
     instance.fDataLocation = (static_cast<int>(fFilterValues.count()) -
                                                filterLength);
     instance.fOffset = filterOffset;
     instance.fTrimmedLength = filterLength;
     instance.fLength = filterSize;
     fFilters.push_back(instance);
     fMaxFilter = SkTMax(fMaxFilter, filterLength);
 }
 const SkConvolutionFilter1D::ConvolutionFixed* SkConvolutionFilter1D::GetSingleFilter(
                                         int* specifiedFilterlength,
                                         int* filterOffset,
                                         int* filterLength) const {
     const FilterInstance& filter = fFilters[0];
     *filterOffset = filter.fOffset;
     *filterLength = filter.fTrimmedLength;
     *specifiedFilterlength = filter.fLength;
     if (filter.fTrimmedLength == 0) {
         return NULL;
     }
     return &fFilterValues[filter.fDataLocation];
 }
 void BGRAConvolve2D(const unsigned char* sourceData,
                     int sourceByteRowStride,
                     bool sourceHasAlpha,
                     const SkConvolutionFilter1D& filterX,
                     const SkConvolutionFilter1D& filterY,
                     int outputByteRowStride,
                     unsigned char* output,
                     const SkConvolutionProcs& convolveProcs,
                     bool useSimdIfPossible) {
     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, filterLength;
     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
     // 16 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() + 15) & ~0xF;
     int rowBufferHeight = maxYFilterSize +
                           (convolveProcs.fConvolve4RowsHorizontally ? 4 : 0);
     CircularRowBuffer rowBuffer(rowBufferWidth,
                                 rowBufferHeight,
                                 filterOffset);
     // Loop over every possible output row, processing just enough horizontal
     // convolutions to run each subsequent vertical convolution.
     SkASSERT(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;
     // SSE2 can access up to 3 extra pixels past the end of the
     // buffer. At the bottom of the image, we have to be careful
     // not to access data past the end of the buffer. Normally
     // we fall back to the C++ implementation for the last row.
     // If the last row is less than 3 pixels wide, we may have to fall
     // back to the C++ version for more rows. Compute how many
     // rows we need to avoid the SSE implementation for here.
     filterX.FilterForValue(filterX.numValues() - 1, &lastFilterOffset,
                            &lastFilterLength);
     int avoidSimdRows = 1 + convolveProcs.fExtraHorizontalReads /
         (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) {
             if (convolveProcs.fConvolve4RowsHorizontally &&
                 nextXRow + 3 < lastFilterOffset + lastFilterLength -
                 avoidSimdRows) {
                 const unsigned char* src[4];
                 unsigned char* outRow[4];
                 for (int i = 0; i < 4; ++i) {
                     src[i] = &sourceData[(nextXRow + i) * sourceByteRowStride];
                     outRow[i] = rowBuffer.advanceRow();
                 }
                 convolveProcs.fConvolve4RowsHorizontally(src, filterX, outRow);
                 nextXRow += 4;
             } else {
                 // Check if we need to avoid SSE2 for this row.
                 if (convolveProcs.fConvolveHorizontally &&
                     nextXRow < lastFilterOffset + lastFilterLength -
                     avoidSimdRows) {
                     convolveProcs.fConvolveHorizontally(
                         &sourceData[nextXRow * sourceByteRowStride],
                         filterX, rowBuffer.advanceRow(), sourceHasAlpha);
                 } else {
                     if (sourceHasAlpha) {
                         ConvolveHorizontally<true>(
                             &sourceData[nextXRow * sourceByteRowStride],
                             filterX, rowBuffer.advanceRow());
                     } else {
                         ConvolveHorizontally<false>(
                             &sourceData[nextXRow * sourceByteRowStride],
                             filterX, rowBuffer.advanceRow());
                     }
                 }
                 nextXRow++;
             }
         }
         // Compute where in the output image this row of final data will go.
         unsigned char* curOutputRow = &output[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];
         if (convolveProcs.fConvolveVertically) {
             convolveProcs.fConvolveVertically(filterValues, filterLength,
                                                firstRowForFilter,
                                                filterX.numValues(), curOutputRow,
                                                sourceHasAlpha);
         } else {
             ConvolveVertically(filterValues, filterLength,
                                firstRowForFilter,
                                filterX.numValues(), curOutputRow,
                                sourceHasAlpha);
         }
     }
 }

The Tor Browser / annotate

gfx/skia/trunk/src/core/SkConvolver.cpp@6474c204b198 (annotated)

gfx/skia/trunk/src/core/SkConvolver.cpp