/*
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* Copyright 2017 Google Inc.
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*
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* Use of this source code is governed by a BSD-style license that can be
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* found in the LICENSE file.
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*/
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#ifndef SkHighContrastFilter_DEFINED
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#define SkHighContrastFilter_DEFINED
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#include "SkColorFilter.h"
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#include "SkPaint.h"
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/**
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* Configuration struct for SkHighContrastFilter.
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*
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* Provides transformations to improve contrast for users with low vision.
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*/
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struct SkHighContrastConfig {
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enum class InvertStyle {
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kNoInvert,
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kInvertBrightness,
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kInvertLightness,
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kLast = kInvertLightness
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};
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SkHighContrastConfig() {
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fGrayscale = false;
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fInvertStyle = InvertStyle::kNoInvert;
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fContrast = 0.0f;
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}
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SkHighContrastConfig(bool grayscale,
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InvertStyle invertStyle,
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SkScalar contrast)
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: fGrayscale(grayscale),
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fInvertStyle(invertStyle),
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fContrast(contrast) {}
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// Returns true if all of the fields are set within the valid range.
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bool isValid() const {
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return fInvertStyle >= InvertStyle::kNoInvert &&
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fInvertStyle <= InvertStyle::kInvertLightness &&
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fContrast >= -1.0 &&
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fContrast <= 1.0;
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}
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// If true, the color will be converted to grayscale.
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bool fGrayscale;
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// Whether to invert brightness, lightness, or neither.
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InvertStyle fInvertStyle;
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// After grayscale and inverting, the contrast can be adjusted linearly.
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// The valid range is -1.0 through 1.0, where 0.0 is no adjustment.
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SkScalar fContrast;
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};
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/**
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* Color filter that provides transformations to improve contrast
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* for users with low vision.
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*
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* Applies the following transformations in this order. Each of these
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* can be configured using SkHighContrastConfig.
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*
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* - Conversion to grayscale
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* - Color inversion (either in RGB or HSL space)
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* - Increasing the resulting contrast.
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*
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* Calling SkHighContrastFilter::Make will return nullptr if the config is
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* not valid, e.g. if you try to call it with a contrast outside the range of
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* -1.0 to 1.0.
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*/
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class SK_API SkHighContrastFilter {
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public:
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// Returns the filter, or nullptr if the config is invalid.
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static sk_sp<SkColorFilter> Make(const SkHighContrastConfig& config);
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static void RegisterFlattenables();
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};
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#endif
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