src/core/SkConvolver.h - skia - Git at Google

 // 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
 #undef FloatToFixed
 #undef FixedToFloat
 #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,
     const SkConvolutionProcs&,
     bool useSimdIfPossible);

 #endif  // SK_CONVOLVER_H
	// 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
	#undef FloatToFixed
	#undef FixedToFloat
	#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,
	const SkConvolutionProcs&,
	bool useSimdIfPossible);

	#endif // SK_CONVOLVER_H