chromium/third_party/skia/src/core/SkBlurEngine.h

/*
 * Copyright 2023 Google LLC
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */

#ifndef SkBlurEngine_DEFINED
#define SkBlurEngine_DEFINED

#include "include/core/SkM44.h"  // IWYU pragma: keep
#include "include/core/SkRefCnt.h"
#include "include/core/SkSize.h"
#include "include/core/SkSpan.h"
#include "include/private/base/SkFloatingPoint.h"

#include <algorithm>
#include <array>
#include <cmath>

class SkDevice;
class SkRuntimeEffect;
class SkRuntimeShaderBuilder;
class SkSpecialImage;
struct SkImageInfo;
struct SkIRect;

enum class SkFilterMode;
enum class SkTileMode;
enum SkColorType : int;

/**
 * SkBlurEngine is a backend-agnostic provider of blur algorithms. Each Skia backend defines a blur
 * engine with a set of supported algorithms and/or implementations. A given implementation may be
 * optimized for a particular color type, sigma range, or available hardware. Each engine and its
 * algorithms are assumed to operate only on SkImages corresponding to its Skia backend, and will
 * produce output SkImages of the same type.
 *
 * Algorithms are allowed to specify a maximum supported sigma. If the desired sigma is higher than
 * this, the input image and output region must be downscaled by the caller before invoking the
 * algorithm. This is to provide the most flexibility for input representation (e.g. directly
 * rasterize at half resolution or apply deferred filter effects during the first downsample pass).
 *
 * skif::FilterResult::Builder::blur() is a convenient wrapper around the blur engine and
 * automatically handles resizing.
*/
class SkBlurEngine { … };

class SkBlurEngine::Algorithm { … };

/**
 * The default blur implementation uses internal runtime effects to evaluate either a single 2D
 * kernel within a shader, or performs two 1D blur passes. This algorithm is backend agnostic but
 * must be subclassed per backend to define the SkDevice creation function.
 */
class SkShaderBlurAlgorithm : public SkBlurEngine::Algorithm { … };

#endif // SkBlurEngine_DEFINED