JUCE/modules/juce_opengl/opengl/juce_OpenGLImage.cpp

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

   This file is part of the JUCE 6 technical preview.
   Copyright (c) 2017 - ROLI Ltd.

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

   For this technical preview, this file is not subject to commercial licensing.

   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
{

class OpenGLFrameBufferImage   : public ImagePixelData
{
public:
    OpenGLFrameBufferImage (OpenGLContext& c, int w, int h)
        : ImagePixelData (Image::ARGB, w, h),
          context (c),
          pixelStride (4),
          lineStride (width * pixelStride)
    {
    }

    bool initialise()
    {
        if (! frameBuffer.initialise (context, width, height))
            return false;

        frameBuffer.clear (Colours::transparentBlack);
        return true;
    }

    std::unique_ptr<LowLevelGraphicsContext> createLowLevelContext() override
    {
        sendDataChangeMessage();
        return createOpenGLGraphicsContext (context, frameBuffer);
    }

    std::unique_ptr<ImageType> createType() const override     { return std::make_unique<OpenGLImageType>(); }

    ImagePixelData::Ptr clone() override
    {
        std::unique_ptr<OpenGLFrameBufferImage> im (new OpenGLFrameBufferImage (context, width, height));

        if (! im->initialise())
            return ImagePixelData::Ptr();

        Image newImage (im.release());
        Graphics g (newImage);
        g.drawImageAt (Image (*this), 0, 0, false);

        return ImagePixelData::Ptr (newImage.getPixelData());
    }

    void initialiseBitmapData (Image::BitmapData& bitmapData, int x, int y, Image::BitmapData::ReadWriteMode mode) override
    {
        bitmapData.pixelFormat = pixelFormat;
        bitmapData.lineStride  = lineStride;
        bitmapData.pixelStride = pixelStride;

        switch (mode)
        {
            case Image::BitmapData::writeOnly:  DataReleaser<Dummy,  Writer>::initialise (frameBuffer, bitmapData, x, y); break;
            case Image::BitmapData::readOnly:   DataReleaser<Reader, Dummy> ::initialise (frameBuffer, bitmapData, x, y); break;
            case Image::BitmapData::readWrite:  DataReleaser<Reader, Writer>::initialise (frameBuffer, bitmapData, x, y); break;
            default:                            jassertfalse; break;
        }

        if (mode != Image::BitmapData::readOnly)
            sendDataChangeMessage();
    }

    OpenGLContext& context;
    OpenGLFrameBuffer frameBuffer;

private:
    int pixelStride, lineStride;

    struct Dummy
    {
        Dummy (OpenGLFrameBuffer&, int, int, int, int) noexcept {}
        static void read (OpenGLFrameBuffer&, Image::BitmapData& , int, int) noexcept {}
        static void write (const PixelARGB*) noexcept {}
    };

    struct Reader
    {
        static void read (OpenGLFrameBuffer& frameBuffer, Image::BitmapData& bitmapData, int x, int y)
        {
            frameBuffer.readPixels ((PixelARGB*) bitmapData.data,
                                    Rectangle<int> (x, frameBuffer.getHeight() - (y + bitmapData.height), bitmapData.width, bitmapData.height));

            verticalRowFlip ((PixelARGB*) bitmapData.data, bitmapData.width, bitmapData.height);
        }

        static void verticalRowFlip (PixelARGB* const data, const int w, const int h)
        {
            HeapBlock<PixelARGB> tempRow (w);
            auto rowSize = (size_t) w * sizeof (PixelARGB);

            for (int y = 0; y < h / 2; ++y)
            {
                PixelARGB* const row1 = data + y * w;
                PixelARGB* const row2 = data + (h - 1 - y) * w;
                memcpy (tempRow, row1, rowSize);
                memcpy (row1, row2, rowSize);
                memcpy (row2, tempRow, rowSize);
            }
        }
    };

    struct Writer
    {
        Writer (OpenGLFrameBuffer& fb, int x, int y, int w, int h) noexcept
            : frameBuffer (fb), area (x, y, w, h)
        {}

        void write (const PixelARGB* const data) const noexcept
        {
            HeapBlock<PixelARGB> invertedCopy (area.getWidth() * area.getHeight());
            auto rowSize = (size_t) area.getWidth() * sizeof (PixelARGB);

            for (int y = 0; y < area.getHeight(); ++y)
                memcpy (invertedCopy + area.getWidth() * y,
                        data + area.getWidth() * (area.getHeight() - 1 - y), rowSize);

            frameBuffer.writePixels (invertedCopy, area);
        }

        OpenGLFrameBuffer& frameBuffer;
        const Rectangle<int> area;

        JUCE_DECLARE_NON_COPYABLE (Writer)
    };

    template <class ReaderType, class WriterType>
    struct DataReleaser  : public Image::BitmapData::BitmapDataReleaser
    {
        DataReleaser (OpenGLFrameBuffer& fb, int x, int y, int w, int h)
            : data ((size_t) (w * h)),
              writer (fb, x, y, w, h)
        {}

        ~DataReleaser()
        {
            writer.write (data);
        }

        static void initialise (OpenGLFrameBuffer& frameBuffer, Image::BitmapData& bitmapData, int x, int y)
        {
            auto* r = new DataReleaser (frameBuffer, x, y, bitmapData.width, bitmapData.height);
            bitmapData.dataReleaser.reset (r);

            bitmapData.data = (uint8*) r->data.get();
            bitmapData.lineStride = (bitmapData.width * bitmapData.pixelStride + 3) & ~3;

            ReaderType::read (frameBuffer, bitmapData, x, y);
        }

        HeapBlock<PixelARGB> data;
        WriterType writer;
    };

    JUCE_DECLARE_NON_COPYABLE_WITH_LEAK_DETECTOR (OpenGLFrameBufferImage)
};


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

int OpenGLImageType::getTypeID() const
{
    return 3;
}

ImagePixelData::Ptr OpenGLImageType::create (Image::PixelFormat, int width, int height, bool /*shouldClearImage*/) const
{
    OpenGLContext* currentContext = OpenGLContext::getCurrentContext();
    jassert (currentContext != nullptr); // an OpenGL image can only be created when a valid context is active!

    std::unique_ptr<OpenGLFrameBufferImage> im (new OpenGLFrameBufferImage (*currentContext, width, height));

    if (! im->initialise())
        return ImagePixelData::Ptr();

    return *im.release();
}

OpenGLFrameBuffer* OpenGLImageType::getFrameBufferFrom (const Image& image)
{
    if (OpenGLFrameBufferImage* const glImage = dynamic_cast<OpenGLFrameBufferImage*> (image.getPixelData()))
        return &(glImage->frameBuffer);

    return nullptr;
}

} // namespace juce