JUCE/modules/juce_graphics/effects/juce_DropShadowEffect.cpp

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

   This file is part of the JUCE 7 technical preview.
   Copyright (c) 2022 - Raw Material Software Limited

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

   For the technical preview this file cannot be licensed commercially.

   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
{

static void blurDataTriplets (uint8* d, int num, const int delta) noexcept
{
    uint32 last = d[0];
    d[0] = (uint8) ((d[0] + d[delta] + 1) / 3);
    d += delta;

    num -= 2;

    do
    {
        const uint32 newLast = d[0];
        d[0] = (uint8) ((last + d[0] + d[delta] + 1) / 3);
        d += delta;
        last = newLast;
    }
    while (--num > 0);

    d[0] = (uint8) ((last + d[0] + 1) / 3);
}

static void blurSingleChannelImage (uint8* const data, const int width, const int height,
                                    const int lineStride, const int repetitions) noexcept
{
    jassert (width > 2 && height > 2);

    for (int y = 0; y < height; ++y)
        for (int i = repetitions; --i >= 0;)
            blurDataTriplets (data + lineStride * y, width, 1);

    for (int x = 0; x < width; ++x)
        for (int i = repetitions; --i >= 0;)
            blurDataTriplets (data + x, height, lineStride);
}

static void blurSingleChannelImage (Image& image, int radius)
{
    const Image::BitmapData bm (image, Image::BitmapData::readWrite);
    blurSingleChannelImage (bm.data, bm.width, bm.height, bm.lineStride, 2 * radius);
}

//==============================================================================
DropShadow::DropShadow (Colour shadowColour, const int r, Point<int> o) noexcept
    : colour (shadowColour), radius (r), offset (o)
{
    jassert (radius > 0);
}

void DropShadow::drawForImage (Graphics& g, const Image& srcImage) const
{
    jassert (radius > 0);

    if (srcImage.isValid())
    {
        Image shadowImage (srcImage.convertedToFormat (Image::SingleChannel));
        shadowImage.duplicateIfShared();

        blurSingleChannelImage (shadowImage, radius);

        g.setColour (colour);
        g.drawImageAt (shadowImage, offset.x, offset.y, true);
    }
}

void DropShadow::drawForPath (Graphics& g, const Path& path) const
{
    jassert (radius > 0);

    auto area = (path.getBounds().getSmallestIntegerContainer() + offset)
                  .expanded (radius + 1)
                  .getIntersection (g.getClipBounds().expanded (radius + 1));

    if (area.getWidth() > 2 && area.getHeight() > 2)
    {
        Image renderedPath (Image::SingleChannel, area.getWidth(), area.getHeight(), true);

        {
            Graphics g2 (renderedPath);
            g2.setColour (Colours::white);
            g2.fillPath (path, AffineTransform::translation ((float) (offset.x - area.getX()),
                                                             (float) (offset.y - area.getY())));
        }

        blurSingleChannelImage (renderedPath, radius);

        g.setColour (colour);
        g.drawImageAt (renderedPath, area.getX(), area.getY(), true);
    }
}

static void drawShadowSection (Graphics& g, ColourGradient& cg, Rectangle<float> area,
                               bool isCorner, float centreX, float centreY, float edgeX, float edgeY)
{
    cg.point1 = area.getRelativePoint (centreX, centreY);
    cg.point2 = area.getRelativePoint (edgeX, edgeY);
    cg.isRadial = isCorner;

    g.setGradientFill (cg);
    g.fillRect (area);
}

void DropShadow::drawForRectangle (Graphics& g, const Rectangle<int>& targetArea) const
{
    ColourGradient cg (colour, 0, 0, colour.withAlpha (0.0f), 0, 0, false);

    for (float i = 0.05f; i < 1.0f; i += 0.1f)
        cg.addColour (1.0 - i, colour.withMultipliedAlpha (i * i));

    const float radiusInset = (float) radius / 2.0f;
    const float expandedRadius = (float) radius + radiusInset;

    auto area = targetArea.toFloat().reduced (radiusInset) + offset.toFloat();

    auto r = area.expanded (expandedRadius);
    auto top = r.removeFromTop (expandedRadius);
    auto bottom = r.removeFromBottom (expandedRadius);

    drawShadowSection (g, cg, top.removeFromLeft  (expandedRadius), true, 1.0f, 1.0f, 0, 1.0f);
    drawShadowSection (g, cg, top.removeFromRight (expandedRadius), true, 0, 1.0f, 1.0f, 1.0f);
    drawShadowSection (g, cg, top, false, 0, 1.0f, 0, 0);

    drawShadowSection (g, cg, bottom.removeFromLeft  (expandedRadius), true, 1.0f, 0, 0, 0);
    drawShadowSection (g, cg, bottom.removeFromRight (expandedRadius), true, 0, 0, 1.0f, 0);
    drawShadowSection (g, cg, bottom, false, 0, 0, 0, 1.0f);

    drawShadowSection (g, cg, r.removeFromLeft  (expandedRadius), false, 1.0f, 0, 0, 0);
    drawShadowSection (g, cg, r.removeFromRight (expandedRadius), false, 0, 0, 1.0f, 0);

    g.setColour (colour);
    g.fillRect (area);
}

//==============================================================================
DropShadowEffect::DropShadowEffect() {}
DropShadowEffect::~DropShadowEffect() {}

void DropShadowEffect::setShadowProperties (const DropShadow& newShadow)
{
    shadow = newShadow;
}

void DropShadowEffect::applyEffect (Image& image, Graphics& g, float scaleFactor, float alpha)
{
    DropShadow s (shadow);
    s.radius = roundToInt ((float) s.radius * scaleFactor);
    s.colour = s.colour.withMultipliedAlpha (alpha);
    s.offset.x = roundToInt ((float) s.offset.x * scaleFactor);
    s.offset.y = roundToInt ((float) s.offset.y * scaleFactor);

    s.drawForImage (g, image);

    g.setOpacity (alpha);
    g.drawImageAt (image, 0, 0);
}

} // namespace juce