SkHighContrastFilter.h

/*
* Copyright 2017 Google Inc.
*
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
*/

#ifndef SkHighContrastFilter_DEFINED
#define SkHighContrastFilter_DEFINED

#include "SkColorFilter.h"
#include "SkPaint.h"

struct SkHighContrastConfig {
    enum class InvertStyle {
        kNoInvert,
        kInvertBrightness,
        kInvertLightness,
    };

    SkHighContrastConfig() {
        fGrayscale = false;
        fInvertStyle = InvertStyle::kNoInvert;
        fContrast = 0.0f;
    }

    SkHighContrastConfig(bool grayscale,
                         InvertStyle invertStyle,
                         SkScalar contrast)
        : fGrayscale(grayscale),
          fInvertStyle(invertStyle),
          fContrast(contrast) {}

    // Returns true if all of the fields are set within the valid range.
    bool isValid() const {
        return fInvertStyle >= InvertStyle::kNoInvert &&
            fInvertStyle <= InvertStyle::kInvertLightness &&
            fContrast >= -1.0 &&
            fContrast <= 1.0;
    }

    // If true, the color will be converted to grayscale.
    bool fGrayscale;

    // Whether to invert brightness, lightness, or neither.
    InvertStyle fInvertStyle;

    // After grayscale and inverting, the contrast can be adjusted linearly.
    // The valid range is -1.0 through 1.0, where 0.0 is no adjustment.
    SkScalar  fContrast;
};

class SK_API SkHighContrastFilter {
public:
    // Returns the filter, or nullptr if the config is invalid.
    static sk_sp<SkColorFilter> Make(const SkHighContrastConfig& config);

    SK_DECLARE_FLATTENABLE_REGISTRAR_GROUP()
};

#endif