JUCE/modules/juce_graphics/effects/juce_DropShadowEffect.h

/*
  ==============================================================================

   This file is part of the JUCE library.
   Copyright (c) 2017 - ROLI Ltd.

   JUCE is an open source library subject to commercial or open-source
   licensing.

   By using JUCE, you agree to the terms of both the JUCE 5 End-User License
   Agreement and JUCE 5 Privacy Policy (both updated and effective as of the
   27th April 2017).

   End User License Agreement: www.juce.com/juce-5-licence
   Privacy Policy: www.juce.com/juce-5-privacy-policy

   Or: You may also use this code under the terms of the GPL v3 (see
   www.gnu.org/licenses).

   JUCE IS PROVIDED "AS IS" WITHOUT ANY WARRANTY, AND ALL WARRANTIES, WHETHER
   EXPRESSED OR IMPLIED, INCLUDING MERCHANTABILITY AND FITNESS FOR PURPOSE, ARE
   DISCLAIMED.

  ==============================================================================
*/

namespace juce
{

//==============================================================================
/**
    Defines a drop-shadow effect.
*/
struct JUCE_API  DropShadow
{
    /** Creates a default drop-shadow effect. */
    DropShadow() noexcept;

    /** Creates a drop-shadow object with the given parameters. */
    DropShadow (Colour shadowColour, int radius, Point<int> offset) noexcept;

    /** Renders a drop-shadow based on the alpha-channel of the given image. */
    void drawForImage (Graphics& g, const Image& srcImage) const;

    /** Renders a drop-shadow based on the shape of a path. */
    void drawForPath (Graphics& g, const Path& path) const;

    /** Renders a drop-shadow for a rectangle.
        Note that for speed, this approximates the shadow using gradients.
    */
    void drawForRectangle (Graphics& g, const Rectangle<int>& area) const;

    /** The colour with which to render the shadow.
        In most cases you'll probably want to leave this as black with an alpha
        value of around 0.5
    */
    Colour colour;

    /** The approximate spread of the shadow. */
    int radius;

    /** The offset of the shadow. */
    Point<int> offset;
};

//==============================================================================
/**
    An effect filter that adds a drop-shadow behind the image's content.

    (This will only work on images/components that aren't opaque, of course).

    When added to a component, this effect will draw a soft-edged
    shadow based on what gets drawn inside it. The shadow will also
    be applied to the component's children.

    For speed, this doesn't use a proper gaussian blur, but cheats by
    using a simple bilinear filter. If you need a really high-quality
    shadow, check out ImageConvolutionKernel::createGaussianBlur()

    @see Component::setComponentEffect
*/
class JUCE_API  DropShadowEffect  : public ImageEffectFilter
{
public:
    //==============================================================================
    /** Creates a default drop-shadow effect.
        To customise the shadow's appearance, use the setShadowProperties() method.
    */
    DropShadowEffect();

    /** Destructor. */
    ~DropShadowEffect();

    //==============================================================================
    /** Sets up parameters affecting the shadow's appearance. */
    void setShadowProperties (const DropShadow& newShadow);

    //==============================================================================
    /** @internal */
    void applyEffect (Image& sourceImage, Graphics& destContext, float scaleFactor, float alpha) override;


private:
    //==============================================================================
    DropShadow shadow;

    JUCE_LEAK_DETECTOR (DropShadowEffect)
};

} // namespace juce