humper@google.com | 138ebc3 | 2013-07-19 20:20:04 +0000 | [diff] [blame] | 1 | // Copyright (c) 2012 The Chromium Authors. All rights reserved. |
| 2 | // Use of this source code is governed by a BSD-style license that can be |
| 3 | // found in the LICENSE file. |
| 4 | |
| 5 | #ifndef SK_CONVOLVER_H |
| 6 | #define SK_CONVOLVER_H |
| 7 | |
| 8 | #include "SkSize.h" |
| 9 | #include "SkTypes.h" |
| 10 | #include "SkTArray.h" |
| 11 | |
| 12 | // avoid confusion with Mac OS X's math library (Carbon) |
| 13 | #if defined(__APPLE__) |
| 14 | #undef FloatToConvolutionFixed |
| 15 | #undef ConvolutionFixedToFloat |
george | ae6a059 | 2014-06-20 06:32:58 -0700 | [diff] [blame] | 16 | #undef FloatToFixed |
| 17 | #undef FixedToFloat |
humper@google.com | 138ebc3 | 2013-07-19 20:20:04 +0000 | [diff] [blame] | 18 | #endif |
| 19 | |
| 20 | // Represents a filter in one dimension. Each output pixel has one entry in this |
| 21 | // object for the filter values contributing to it. You build up the filter |
| 22 | // list by calling AddFilter for each output pixel (in order). |
| 23 | // |
| 24 | // We do 2-dimensional convolution by first convolving each row by one |
| 25 | // SkConvolutionFilter1D, then convolving each column by another one. |
| 26 | // |
| 27 | // Entries are stored in ConvolutionFixed point, shifted left by kShiftBits. |
| 28 | class SkConvolutionFilter1D { |
| 29 | public: |
| 30 | typedef short ConvolutionFixed; |
| 31 | |
| 32 | // The number of bits that ConvolutionFixed point values are shifted by. |
| 33 | enum { kShiftBits = 14 }; |
| 34 | |
| 35 | SK_API SkConvolutionFilter1D(); |
| 36 | SK_API ~SkConvolutionFilter1D(); |
| 37 | |
| 38 | // Convert between floating point and our ConvolutionFixed point representation. |
| 39 | static ConvolutionFixed FloatToFixed(float f) { |
| 40 | return static_cast<ConvolutionFixed>(f * (1 << kShiftBits)); |
| 41 | } |
| 42 | static unsigned char FixedToChar(ConvolutionFixed x) { |
| 43 | return static_cast<unsigned char>(x >> kShiftBits); |
| 44 | } |
| 45 | static float FixedToFloat(ConvolutionFixed x) { |
| 46 | // The cast relies on ConvolutionFixed being a short, implying that on |
| 47 | // the platforms we care about all (16) bits will fit into |
| 48 | // the mantissa of a (32-bit) float. |
| 49 | SK_COMPILE_ASSERT(sizeof(ConvolutionFixed) == 2, ConvolutionFixed_type_should_fit_in_float_mantissa); |
| 50 | float raw = static_cast<float>(x); |
| 51 | return ldexpf(raw, -kShiftBits); |
| 52 | } |
| 53 | |
| 54 | // Returns the maximum pixel span of a filter. |
| 55 | int maxFilter() const { return fMaxFilter; } |
| 56 | |
| 57 | // Returns the number of filters in this filter. This is the dimension of the |
| 58 | // output image. |
| 59 | int numValues() const { return static_cast<int>(fFilters.count()); } |
| 60 | |
| 61 | // Appends the given list of scaling values for generating a given output |
| 62 | // pixel. |filterOffset| is the distance from the edge of the image to where |
| 63 | // the scaling factors start. The scaling factors apply to the source pixels |
| 64 | // starting from this position, and going for the next |filterLength| pixels. |
| 65 | // |
| 66 | // You will probably want to make sure your input is normalized (that is, |
| 67 | // all entries in |filterValuesg| sub to one) to prevent affecting the overall |
| 68 | // brighness of the image. |
| 69 | // |
| 70 | // The filterLength must be > 0. |
| 71 | // |
| 72 | // This version will automatically convert your input to ConvolutionFixed point. |
| 73 | SK_API void AddFilter(int filterOffset, |
| 74 | const float* filterValues, |
| 75 | int filterLength); |
| 76 | |
| 77 | // Same as the above version, but the input is already ConvolutionFixed point. |
| 78 | void AddFilter(int filterOffset, |
| 79 | const ConvolutionFixed* filterValues, |
| 80 | int filterLength); |
| 81 | |
| 82 | // Retrieves a filter for the given |valueOffset|, a position in the output |
| 83 | // image in the direction we're convolving. The offset and length of the |
| 84 | // filter values are put into the corresponding out arguments (see AddFilter |
| 85 | // above for what these mean), and a pointer to the first scaling factor is |
| 86 | // returned. There will be |filterLength| values in this array. |
skia.committer@gmail.com | 1f3c738 | 2013-07-20 07:00:58 +0000 | [diff] [blame] | 87 | inline const ConvolutionFixed* FilterForValue(int valueOffset, |
humper@google.com | 138ebc3 | 2013-07-19 20:20:04 +0000 | [diff] [blame] | 88 | int* filterOffset, |
| 89 | int* filterLength) const { |
| 90 | const FilterInstance& filter = fFilters[valueOffset]; |
| 91 | *filterOffset = filter.fOffset; |
| 92 | *filterLength = filter.fTrimmedLength; |
| 93 | if (filter.fTrimmedLength == 0) { |
| 94 | return NULL; |
| 95 | } |
| 96 | return &fFilterValues[filter.fDataLocation]; |
| 97 | } |
| 98 | |
| 99 | // Retrieves the filter for the offset 0, presumed to be the one and only. |
| 100 | // The offset and length of the filter values are put into the corresponding |
| 101 | // out arguments (see AddFilter). Note that |filterLegth| and |
| 102 | // |specifiedFilterLength| may be different if leading/trailing zeros of the |
| 103 | // original floating point form were clipped. |
| 104 | // There will be |filterLength| values in the return array. |
| 105 | // Returns NULL if the filter is 0-length (for instance when all floating |
| 106 | // point values passed to AddFilter were clipped to 0). |
| 107 | SK_API const ConvolutionFixed* GetSingleFilter(int* specifiedFilterLength, |
| 108 | int* filterOffset, |
| 109 | int* filterLength) const; |
| 110 | |
skia.committer@gmail.com | 1f3c738 | 2013-07-20 07:00:58 +0000 | [diff] [blame] | 111 | // Add another value to the fFilterValues array -- useful for |
humper@google.com | 138ebc3 | 2013-07-19 20:20:04 +0000 | [diff] [blame] | 112 | // SIMD padding which happens outside of this class. |
skia.committer@gmail.com | 1f3c738 | 2013-07-20 07:00:58 +0000 | [diff] [blame] | 113 | |
humper@google.com | 138ebc3 | 2013-07-19 20:20:04 +0000 | [diff] [blame] | 114 | void addFilterValue( ConvolutionFixed val ) { |
| 115 | fFilterValues.push_back( val ); |
| 116 | } |
| 117 | private: |
| 118 | struct FilterInstance { |
| 119 | // Offset within filterValues for this instance of the filter. |
| 120 | int fDataLocation; |
| 121 | |
| 122 | // Distance from the left of the filter to the center. IN PIXELS |
| 123 | int fOffset; |
| 124 | |
| 125 | // Number of values in this filter instance. |
| 126 | int fTrimmedLength; |
| 127 | |
| 128 | // Filter length as specified. Note that this may be different from |
| 129 | // 'trimmed_length' if leading/trailing zeros of the original floating |
| 130 | // point form were clipped differently on each tail. |
| 131 | int fLength; |
| 132 | }; |
| 133 | |
| 134 | // Stores the information for each filter added to this class. |
| 135 | SkTArray<FilterInstance> fFilters; |
| 136 | |
| 137 | // We store all the filter values in this flat list, indexed by |
| 138 | // |FilterInstance.data_location| to avoid the mallocs required for storing |
| 139 | // each one separately. |
| 140 | SkTArray<ConvolutionFixed> fFilterValues; |
| 141 | |
| 142 | // The maximum size of any filter we've added. |
| 143 | int fMaxFilter; |
| 144 | }; |
| 145 | |
| 146 | typedef void (*SkConvolveVertically_pointer)( |
| 147 | const SkConvolutionFilter1D::ConvolutionFixed* filterValues, |
| 148 | int filterLength, |
| 149 | unsigned char* const* sourceDataRows, |
| 150 | int pixelWidth, |
| 151 | unsigned char* outRow, |
| 152 | bool hasAlpha); |
| 153 | typedef void (*SkConvolve4RowsHorizontally_pointer)( |
| 154 | const unsigned char* srcData[4], |
| 155 | const SkConvolutionFilter1D& filter, |
| 156 | unsigned char* outRow[4]); |
| 157 | typedef void (*SkConvolveHorizontally_pointer)( |
| 158 | const unsigned char* srcData, |
| 159 | const SkConvolutionFilter1D& filter, |
| 160 | unsigned char* outRow, |
| 161 | bool hasAlpha); |
| 162 | typedef void (*SkConvolveFilterPadding_pointer)( |
| 163 | SkConvolutionFilter1D* filter); |
| 164 | |
| 165 | struct SkConvolutionProcs { |
| 166 | // This is how many extra pixels may be read by the |
| 167 | // conolve*horizontally functions. |
| 168 | int fExtraHorizontalReads; |
| 169 | SkConvolveVertically_pointer fConvolveVertically; |
| 170 | SkConvolve4RowsHorizontally_pointer fConvolve4RowsHorizontally; |
| 171 | SkConvolveHorizontally_pointer fConvolveHorizontally; |
| 172 | SkConvolveFilterPadding_pointer fApplySIMDPadding; |
| 173 | }; |
| 174 | |
| 175 | |
| 176 | |
| 177 | // Does a two-dimensional convolution on the given source image. |
| 178 | // |
| 179 | // It is assumed the source pixel offsets referenced in the input filters |
| 180 | // reference only valid pixels, so the source image size is not required. Each |
| 181 | // row of the source image starts |sourceByteRowStride| after the previous |
| 182 | // one (this allows you to have rows with some padding at the end). |
| 183 | // |
| 184 | // The result will be put into the given output buffer. The destination image |
| 185 | // size will be xfilter.numValues() * yfilter.numValues() pixels. It will be |
| 186 | // in rows of exactly xfilter.numValues() * 4 bytes. |
| 187 | // |
| 188 | // |sourceHasAlpha| is a hint that allows us to avoid doing computations on |
| 189 | // the alpha channel if the image is opaque. If you don't know, set this to |
| 190 | // true and it will work properly, but setting this to false will be a few |
| 191 | // percent faster if you know the image is opaque. |
| 192 | // |
| 193 | // The layout in memory is assumed to be 4-bytes per pixel in B-G-R-A order |
| 194 | // (this is ARGB when loaded into 32-bit words on a little-endian machine). |
| 195 | SK_API void BGRAConvolve2D(const unsigned char* sourceData, |
| 196 | int sourceByteRowStride, |
| 197 | bool sourceHasAlpha, |
| 198 | const SkConvolutionFilter1D& xfilter, |
| 199 | const SkConvolutionFilter1D& yfilter, |
| 200 | int outputByteRowStride, |
| 201 | unsigned char* output, |
reed@google.com | fed04b3 | 2013-09-05 20:31:17 +0000 | [diff] [blame] | 202 | const SkConvolutionProcs&, |
humper@google.com | 138ebc3 | 2013-07-19 20:20:04 +0000 | [diff] [blame] | 203 | bool useSimdIfPossible); |
| 204 | |
| 205 | #endif // SK_CONVOLVER_H |