diff options
Diffstat (limited to 'src/core/SkConvolver.h')
-rw-r--r-- | src/core/SkConvolver.h | 203 |
1 files changed, 203 insertions, 0 deletions
diff --git a/src/core/SkConvolver.h b/src/core/SkConvolver.h new file mode 100644 index 0000000000..a2758e57a8 --- /dev/null +++ b/src/core/SkConvolver.h @@ -0,0 +1,203 @@ +// Copyright (c) 2012 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. + +#ifndef SK_CONVOLVER_H +#define SK_CONVOLVER_H + +#include "SkSize.h" +#include "SkTypes.h" +#include "SkTArray.h" + +// avoid confusion with Mac OS X's math library (Carbon) +#if defined(__APPLE__) +#undef FloatToConvolutionFixed +#undef ConvolutionFixedToFloat +#endif + +// Represents a filter in one dimension. Each output pixel has one entry in this +// object for the filter values contributing to it. You build up the filter +// list by calling AddFilter for each output pixel (in order). +// +// We do 2-dimensional convolution by first convolving each row by one +// SkConvolutionFilter1D, then convolving each column by another one. +// +// Entries are stored in ConvolutionFixed point, shifted left by kShiftBits. +class SkConvolutionFilter1D { +public: + typedef short ConvolutionFixed; + + // The number of bits that ConvolutionFixed point values are shifted by. + enum { kShiftBits = 14 }; + + SK_API SkConvolutionFilter1D(); + SK_API ~SkConvolutionFilter1D(); + + // Convert between floating point and our ConvolutionFixed point representation. + static ConvolutionFixed FloatToFixed(float f) { + return static_cast<ConvolutionFixed>(f * (1 << kShiftBits)); + } + static unsigned char FixedToChar(ConvolutionFixed x) { + return static_cast<unsigned char>(x >> kShiftBits); + } + static float FixedToFloat(ConvolutionFixed x) { + // The cast relies on ConvolutionFixed being a short, implying that on + // the platforms we care about all (16) bits will fit into + // the mantissa of a (32-bit) float. + SK_COMPILE_ASSERT(sizeof(ConvolutionFixed) == 2, ConvolutionFixed_type_should_fit_in_float_mantissa); + float raw = static_cast<float>(x); + return ldexpf(raw, -kShiftBits); + } + + // Returns the maximum pixel span of a filter. + int maxFilter() const { return fMaxFilter; } + + // Returns the number of filters in this filter. This is the dimension of the + // output image. + int numValues() const { return static_cast<int>(fFilters.count()); } + + // Appends the given list of scaling values for generating a given output + // pixel. |filterOffset| is the distance from the edge of the image to where + // the scaling factors start. The scaling factors apply to the source pixels + // starting from this position, and going for the next |filterLength| pixels. + // + // You will probably want to make sure your input is normalized (that is, + // all entries in |filterValuesg| sub to one) to prevent affecting the overall + // brighness of the image. + // + // The filterLength must be > 0. + // + // This version will automatically convert your input to ConvolutionFixed point. + SK_API void AddFilter(int filterOffset, + const float* filterValues, + int filterLength); + + // Same as the above version, but the input is already ConvolutionFixed point. + void AddFilter(int filterOffset, + const ConvolutionFixed* filterValues, + int filterLength); + + // Retrieves a filter for the given |valueOffset|, a position in the output + // image in the direction we're convolving. The offset and length of the + // filter values are put into the corresponding out arguments (see AddFilter + // above for what these mean), and a pointer to the first scaling factor is + // returned. There will be |filterLength| values in this array. + inline const ConvolutionFixed* FilterForValue(int valueOffset, + int* filterOffset, + int* filterLength) const { + const FilterInstance& filter = fFilters[valueOffset]; + *filterOffset = filter.fOffset; + *filterLength = filter.fTrimmedLength; + if (filter.fTrimmedLength == 0) { + return NULL; + } + return &fFilterValues[filter.fDataLocation]; + } + + // Retrieves the filter for the offset 0, presumed to be the one and only. + // The offset and length of the filter values are put into the corresponding + // out arguments (see AddFilter). Note that |filterLegth| and + // |specifiedFilterLength| may be different if leading/trailing zeros of the + // original floating point form were clipped. + // There will be |filterLength| values in the return array. + // Returns NULL if the filter is 0-length (for instance when all floating + // point values passed to AddFilter were clipped to 0). + SK_API const ConvolutionFixed* GetSingleFilter(int* specifiedFilterLength, + int* filterOffset, + int* filterLength) const; + + // Add another value to the fFilterValues array -- useful for + // SIMD padding which happens outside of this class. + + void addFilterValue( ConvolutionFixed val ) { + fFilterValues.push_back( val ); + } +private: + struct FilterInstance { + // Offset within filterValues for this instance of the filter. + int fDataLocation; + + // Distance from the left of the filter to the center. IN PIXELS + int fOffset; + + // Number of values in this filter instance. + int fTrimmedLength; + + // Filter length as specified. Note that this may be different from + // 'trimmed_length' if leading/trailing zeros of the original floating + // point form were clipped differently on each tail. + int fLength; + }; + + // Stores the information for each filter added to this class. + SkTArray<FilterInstance> fFilters; + + // We store all the filter values in this flat list, indexed by + // |FilterInstance.data_location| to avoid the mallocs required for storing + // each one separately. + SkTArray<ConvolutionFixed> fFilterValues; + + // The maximum size of any filter we've added. + int fMaxFilter; +}; + +typedef void (*SkConvolveVertically_pointer)( + const SkConvolutionFilter1D::ConvolutionFixed* filterValues, + int filterLength, + unsigned char* const* sourceDataRows, + int pixelWidth, + unsigned char* outRow, + bool hasAlpha); +typedef void (*SkConvolve4RowsHorizontally_pointer)( + const unsigned char* srcData[4], + const SkConvolutionFilter1D& filter, + unsigned char* outRow[4]); +typedef void (*SkConvolveHorizontally_pointer)( + const unsigned char* srcData, + const SkConvolutionFilter1D& filter, + unsigned char* outRow, + bool hasAlpha); +typedef void (*SkConvolveFilterPadding_pointer)( + SkConvolutionFilter1D* filter); + +struct SkConvolutionProcs { + // This is how many extra pixels may be read by the + // conolve*horizontally functions. + int fExtraHorizontalReads; + SkConvolveVertically_pointer fConvolveVertically; + SkConvolve4RowsHorizontally_pointer fConvolve4RowsHorizontally; + SkConvolveHorizontally_pointer fConvolveHorizontally; + SkConvolveFilterPadding_pointer fApplySIMDPadding; +}; + + + +// 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). +SK_API void BGRAConvolve2D(const unsigned char* sourceData, + int sourceByteRowStride, + bool sourceHasAlpha, + const SkConvolutionFilter1D& xfilter, + const SkConvolutionFilter1D& yfilter, + int outputByteRowStride, + unsigned char* output, + SkConvolutionProcs* convolveProcs, + bool useSimdIfPossible); + +#endif // SK_CONVOLVER_H |