chromium/skia/ext/convolver.h

// Copyright 2012 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef SKIA_EXT_CONVOLVER_H_
#define SKIA_EXT_CONVOLVER_H_

#include <stdint.h>

#include <cmath>
#include <vector>

#include "build/build_config.h"
#include "third_party/skia/include/core/SkSize.h"
#include "third_party/skia/include/core/SkTypes.h"

// We can build SSE2 optimized versions for all x86 CPUs
// except when building for the IOS emulator.
#if defined(ARCH_CPU_X86_FAMILY) && !BUILDFLAG(IS_IOS)
#define SIMD_SSE2 …
#define SIMD_PADDING …
#endif

#if defined (ARCH_CPU_MIPS_FAMILY) && \
    defined(__mips_dsp) && (__mips_dsp_rev >= 2)
#define SIMD_MIPS_DSPR2 …
#endif

#if defined(ARCH_CPU_ARM_FAMILY) && \
    (defined(__ARM_NEON__) || defined(__ARM_NEON))
#define SIMD_NEON …
#endif

#if defined(ARCH_CPU_LOONGARCH_FAMILY) && defined(__loongarch_sx)
#define SIMD_LSX …
#endif

// avoid confusion with Mac OS X's math library (Carbon)
#if defined(__APPLE__)
#undef FloatToFixed
#undef FixedToFloat
#endif

namespace skia {

// 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
// ConvolutionFilter1D, then convolving each column by another one.
//
// Entries are stored in fixed point, shifted left by kShiftBits.
class ConvolutionFilter1D { … };

// 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 |source_byte_row_stride| 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.num_values() * yfilter.num_values() pixels. It will be
// in rows of exactly xfilter.num_values() * 4 bytes.
//
// |source_has_alpha| 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* source_data,
                           int source_byte_row_stride,
                           bool source_has_alpha,
                           const ConvolutionFilter1D& xfilter,
                           const ConvolutionFilter1D& yfilter,
                           int output_byte_row_stride,
                           unsigned char* output,
                           bool use_simd_if_possible);

// Does a 1D convolution of the given source image along the X dimension on
// a single channel of the bitmap.
//
// The function uses the same convolution kernel for each pixel. That kernel
// must be added to |filter| at offset 0. This is a most straightforward
// implementation of convolution, intended chiefly for development purposes.
SK_API void SingleChannelConvolveX1D(const unsigned char* source_data,
                                     int source_byte_row_stride,
                                     int input_channel_index,
                                     int input_channel_count,
                                     const ConvolutionFilter1D& filter,
                                     const SkISize& image_size,
                                     unsigned char* output,
                                     int output_byte_row_stride,
                                     int output_channel_index,
                                     int output_channel_count,
                                     bool absolute_values);

// Does a 1D convolution of the given source image along the Y dimension on
// a single channel of the bitmap.
SK_API void SingleChannelConvolveY1D(const unsigned char* source_data,
                                     int source_byte_row_stride,
                                     int input_channel_index,
                                     int input_channel_count,
                                     const ConvolutionFilter1D& filter,
                                     const SkISize& image_size,
                                     unsigned char* output,
                                     int output_byte_row_stride,
                                     int output_channel_index,
                                     int output_channel_count,
                                     bool absolute_values);

// Set up the |filter| instance with a gaussian kernel. |kernel_sigma| is the
// parameter of gaussian. If |derivative| is true, the kernel will be that of
// the first derivative. Intended for use with the two routines above.
SK_API void SetUpGaussianConvolutionKernel(ConvolutionFilter1D* filter,
                                           float kernel_sigma,
                                           bool derivative);

}  // namespace skia

#endif  // SKIA_EXT_CONVOLVER_H_