chromium/third_party/skia/modules/skottie/src/effects/BlackAndWhiteEffect.cpp

/*
 * Copyright 2020 Google Inc.
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */

#include "include/core/SkData.h"
#include "include/core/SkRefCnt.h"
#include "include/core/SkString.h"
#include "include/effects/SkRuntimeEffect.h"
#include "include/private/base/SkAssert.h"
#include "modules/skottie/src/Adapter.h"
#include "modules/skottie/src/SkottiePriv.h"
#include "modules/skottie/src/SkottieValue.h"
#include "modules/skottie/src/effects/Effects.h"
#include "modules/sksg/include/SkSGColorFilter.h"
#include "modules/sksg/include/SkSGRenderNode.h"

#include <cstddef>
#include <utility>

namespace skjson {
class ArrayValue;
}

namespace skottie::internal {
namespace {

// The B&W effect allows controlling individual luminance contribution of
// primary and secondary colors.
//
// The implementation relies on computing primary/secondary relative weights
// for the input color on the hue hexagon, and modulating based on weight
// coefficients.
//
// Note:
//   - at least one of (dr,dg,db) is 0
//   - at least two of (wr,wg,wb) and two of (wy,wc,wm) are 0
//  => we are effectively selecting the color hue sextant without explicit branching
//
// (inspired by https://github.com/RoyiAvital/StackExchangeCodes/blob/master/SignalProcessing/Q688/ApplyBlackWhiteFilter.m)

static sk_sp<SkRuntimeEffect> make_effect() { … }

class BlackAndWhiteAdapter final : public DiscardableAdapterBase<BlackAndWhiteAdapter,
                                                                 sksg::ExternalColorFilter> { … };

} // namespace

sk_sp<sksg::RenderNode> EffectBuilder::attachBlackAndWhiteEffect(
        const skjson::ArrayValue& jprops, sk_sp<sksg::RenderNode> layer) const { … }

} // namespace skottie::internal