composition.cpp Example File

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 #include "composition.h"
 #include <QBoxLayout>
 #include <QRadioButton>
 #include <QTimer>
 #include <QDateTime>
 #include <QSlider>
 #include <QMouseEvent>
 #include <qmath.h>

 #if QT_CONFIG(opengl)
 #include <QOpenGLFunctions>
 #include <QOpenGLWindow>
 #endif

 const int animationInterval = 15; // update every 16 ms = ~60FPS

 CompositionWidget::CompositionWidget(QWidget *parent)
     : QWidget(parent)
 {
     CompositionRenderer *view = new CompositionRenderer(this);

     QGroupBox *mainGroup = new QGroupBox(parent);
     mainGroup->setTitle(tr("Composition Modes"));

     QGroupBox *modesGroup = new QGroupBox(mainGroup);
     modesGroup->setTitle(tr("Mode"));

     rbClear = new QRadioButton(tr("Clear"), modesGroup);
     connect(rbClear, SIGNAL(clicked()), view, SLOT(setClearMode()));
     rbSource = new QRadioButton(tr("Source"), modesGroup);
     connect(rbSource, SIGNAL(clicked()), view, SLOT(setSourceMode()));
     rbDest = new QRadioButton(tr("Destination"), modesGroup);
     connect(rbDest, SIGNAL(clicked()), view, SLOT(setDestMode()));
     rbSourceOver = new QRadioButton(tr("Source Over"), modesGroup);
     connect(rbSourceOver, SIGNAL(clicked()), view, SLOT(setSourceOverMode()));
     rbDestOver = new QRadioButton(tr("Destination Over"), modesGroup);
     connect(rbDestOver, SIGNAL(clicked()), view, SLOT(setDestOverMode()));
     rbSourceIn = new QRadioButton(tr("Source In"), modesGroup);
     connect(rbSourceIn, SIGNAL(clicked()), view, SLOT(setSourceInMode()));
     rbDestIn = new QRadioButton(tr("Dest In"), modesGroup);
     connect(rbDestIn, SIGNAL(clicked()), view, SLOT(setDestInMode()));
     rbSourceOut = new QRadioButton(tr("Source Out"), modesGroup);
     connect(rbSourceOut, SIGNAL(clicked()), view, SLOT(setSourceOutMode()));
     rbDestOut = new QRadioButton(tr("Dest Out"), modesGroup);
     connect(rbDestOut, SIGNAL(clicked()), view, SLOT(setDestOutMode()));
     rbSourceAtop = new QRadioButton(tr("Source Atop"), modesGroup);
     connect(rbSourceAtop, SIGNAL(clicked()), view, SLOT(setSourceAtopMode()));
     rbDestAtop = new QRadioButton(tr("Dest Atop"), modesGroup);
     connect(rbDestAtop, SIGNAL(clicked()), view, SLOT(setDestAtopMode()));
     rbXor = new QRadioButton(tr("Xor"), modesGroup);
     connect(rbXor, SIGNAL(clicked()), view, SLOT(setXorMode()));

     rbPlus = new QRadioButton(tr("Plus"), modesGroup);
     connect(rbPlus, SIGNAL(clicked()), view, SLOT(setPlusMode()));
     rbMultiply = new QRadioButton(tr("Multiply"), modesGroup);
     connect(rbMultiply, SIGNAL(clicked()), view, SLOT(setMultiplyMode()));
     rbScreen = new QRadioButton(tr("Screen"), modesGroup);
     connect(rbScreen, SIGNAL(clicked()), view, SLOT(setScreenMode()));
     rbOverlay = new QRadioButton(tr("Overlay"), modesGroup);
     connect(rbOverlay, SIGNAL(clicked()), view, SLOT(setOverlayMode()));
     rbDarken = new QRadioButton(tr("Darken"), modesGroup);
     connect(rbDarken, SIGNAL(clicked()), view, SLOT(setDarkenMode()));
     rbLighten = new QRadioButton(tr("Lighten"), modesGroup);
     connect(rbLighten, SIGNAL(clicked()), view, SLOT(setLightenMode()));
     rbColorDodge = new QRadioButton(tr("Color Dodge"), modesGroup);
     connect(rbColorDodge, SIGNAL(clicked()), view, SLOT(setColorDodgeMode()));
     rbColorBurn = new QRadioButton(tr("Color Burn"), modesGroup);
     connect(rbColorBurn, SIGNAL(clicked()), view, SLOT(setColorBurnMode()));
     rbHardLight = new QRadioButton(tr("Hard Light"), modesGroup);
     connect(rbHardLight, SIGNAL(clicked()), view, SLOT(setHardLightMode()));
     rbSoftLight = new QRadioButton(tr("Soft Light"), modesGroup);
     connect(rbSoftLight, SIGNAL(clicked()), view, SLOT(setSoftLightMode()));
     rbDifference = new QRadioButton(tr("Difference"), modesGroup);
     connect(rbDifference, SIGNAL(clicked()), view, SLOT(setDifferenceMode()));
     rbExclusion = new QRadioButton(tr("Exclusion"), modesGroup);
     connect(rbExclusion, SIGNAL(clicked()), view, SLOT(setExclusionMode()));

     QGroupBox *circleColorGroup = new QGroupBox(mainGroup);
     circleColorGroup->setTitle(tr("Circle color"));
     QSlider *circleColorSlider = new QSlider(Qt::Horizontal, circleColorGroup);
     circleColorSlider->setRange(0, 359);
     circleColorSlider->setSizePolicy(QSizePolicy::Preferred, QSizePolicy::Fixed);
     connect(circleColorSlider, SIGNAL(valueChanged(int)), view, SLOT(setCircleColor(int)));

     QGroupBox *circleAlphaGroup = new QGroupBox(mainGroup);
     circleAlphaGroup->setTitle(tr("Circle alpha"));
     QSlider *circleAlphaSlider = new QSlider(Qt::Horizontal, circleAlphaGroup);
     circleAlphaSlider->setRange(0, 255);
     circleAlphaSlider->setSizePolicy(QSizePolicy::Preferred, QSizePolicy::Fixed);
     connect(circleAlphaSlider, SIGNAL(valueChanged(int)), view, SLOT(setCircleAlpha(int)));

     QPushButton *showSourceButton = new QPushButton(mainGroup);
     showSourceButton->setText(tr("Show Source"));
 #if QT_CONFIG(opengl)
     QPushButton *enableOpenGLButton = new QPushButton(mainGroup);
     enableOpenGLButton->setText(tr("Use OpenGL"));
     enableOpenGLButton->setCheckable(true);
     enableOpenGLButton->setChecked(view->usesOpenGL());
 #endif
     QPushButton *whatsThisButton = new QPushButton(mainGroup);
     whatsThisButton->setText(tr("What's This?"));
     whatsThisButton->setCheckable(true);

     QPushButton *animateButton = new QPushButton(mainGroup);
     animateButton->setText(tr("Animated"));
     animateButton->setCheckable(true);
     animateButton->setChecked(true);

     QHBoxLayout *viewLayout = new QHBoxLayout(this);
     viewLayout->addWidget(view);
     viewLayout->addWidget(mainGroup);

     QVBoxLayout *mainGroupLayout = new QVBoxLayout(mainGroup);
     mainGroupLayout->addWidget(circleColorGroup);
     mainGroupLayout->addWidget(circleAlphaGroup);
     mainGroupLayout->addWidget(modesGroup);
     mainGroupLayout->addStretch();
     mainGroupLayout->addWidget(animateButton);
     mainGroupLayout->addWidget(whatsThisButton);
     mainGroupLayout->addWidget(showSourceButton);
 #if QT_CONFIG(opengl)
     mainGroupLayout->addWidget(enableOpenGLButton);
 #endif

     QGridLayout *modesLayout = new QGridLayout(modesGroup);
     modesLayout->addWidget(rbClear, 0, 0);
     modesLayout->addWidget(rbSource, 1, 0);
     modesLayout->addWidget(rbDest, 2, 0);
     modesLayout->addWidget(rbSourceOver, 3, 0);
     modesLayout->addWidget(rbDestOver, 4, 0);
     modesLayout->addWidget(rbSourceIn, 5, 0);
     modesLayout->addWidget(rbDestIn, 6, 0);
     modesLayout->addWidget(rbSourceOut, 7, 0);
     modesLayout->addWidget(rbDestOut, 8, 0);
     modesLayout->addWidget(rbSourceAtop, 9, 0);
     modesLayout->addWidget(rbDestAtop, 10, 0);
     modesLayout->addWidget(rbXor, 11, 0);

     modesLayout->addWidget(rbPlus, 0, 1);
     modesLayout->addWidget(rbMultiply, 1, 1);
     modesLayout->addWidget(rbScreen, 2, 1);
     modesLayout->addWidget(rbOverlay, 3, 1);
     modesLayout->addWidget(rbDarken, 4, 1);
     modesLayout->addWidget(rbLighten, 5, 1);
     modesLayout->addWidget(rbColorDodge, 6, 1);
     modesLayout->addWidget(rbColorBurn, 7, 1);
     modesLayout->addWidget(rbHardLight, 8, 1);
     modesLayout->addWidget(rbSoftLight, 9, 1);
     modesLayout->addWidget(rbDifference, 10, 1);
     modesLayout->addWidget(rbExclusion, 11, 1);

     QVBoxLayout *circleColorLayout = new QVBoxLayout(circleColorGroup);
     circleColorLayout->addWidget(circleColorSlider);

     QVBoxLayout *circleAlphaLayout = new QVBoxLayout(circleAlphaGroup);
     circleAlphaLayout->addWidget(circleAlphaSlider);

     view->loadDescription(":res/composition/composition.html");
     view->loadSourceFile(":res/composition/composition.cpp");

     connect(whatsThisButton, SIGNAL(clicked(bool)), view, SLOT(setDescriptionEnabled(bool)));
     connect(view, SIGNAL(descriptionEnabledChanged(bool)), whatsThisButton, SLOT(setChecked(bool)));
     connect(showSourceButton, SIGNAL(clicked()), view, SLOT(showSource()));
 #if QT_CONFIG(opengl)
     connect(enableOpenGLButton, SIGNAL(clicked(bool)), view, SLOT(enableOpenGL(bool)));
 #endif
     connect(animateButton, SIGNAL(toggled(bool)), view, SLOT(setAnimationEnabled(bool)));

     circleColorSlider->setValue(270);
     circleAlphaSlider->setValue(200);
     rbSourceOut->animateClick();

     setWindowTitle(tr("Composition Modes"));
 }

 void CompositionWidget::nextMode()
 {
     /*
       if (!m_animation_enabled)
       return;
       if (rbClear->isChecked()) rbSource->animateClick();
       if (rbSource->isChecked()) rbDest->animateClick();
       if (rbDest->isChecked()) rbSourceOver->animateClick();
       if (rbSourceOver->isChecked()) rbDestOver->animateClick();
       if (rbDestOver->isChecked()) rbSourceIn->animateClick();
       if (rbSourceIn->isChecked()) rbDestIn->animateClick();
       if (rbDestIn->isChecked()) rbSourceOut->animateClick();
       if (rbSourceOut->isChecked()) rbDestOut->animateClick();
       if (rbDestOut->isChecked()) rbSourceAtop->animateClick();
       if (rbSourceAtop->isChecked()) rbDestAtop->animateClick();
       if (rbDestAtop->isChecked()) rbXor->animateClick();
       if (rbXor->isChecked()) rbClear->animateClick();
     */
 }

 CompositionRenderer::CompositionRenderer(QWidget *parent)
     : ArthurFrame(parent)
 {
     m_animation_enabled = true;
     m_animationTimer = startTimer(animationInterval);
     m_image = QImage(":res/composition/flower.jpg");
     m_image.setAlphaChannel(QImage(":res/composition/flower_alpha.jpg"));
     m_circle_alpha = 127;
     m_circle_hue = 255;
     m_current_object = NoObject;
     m_composition_mode = QPainter::CompositionMode_SourceOut;

     m_circle_pos = QPoint(200, 100);

     setSizePolicy(QSizePolicy::Expanding, QSizePolicy::Expanding);
 #if QT_CONFIG(opengl)
     m_pbuffer_size = 1024;
 #endif
 }

 QRectF rectangle_around(const QPointF &p, const QSizeF &size = QSize(250, 200))
 {
     QRectF rect(p, size);
     rect.translate(-size.width()/2, -size.height()/2);
     return rect;
 }

 void CompositionRenderer::setAnimationEnabled(bool enabled)
 {
     if (m_animation_enabled == enabled)
         return;
     m_animation_enabled = enabled;
     if (enabled) {
         Q_ASSERT(!m_animationTimer);
         m_animationTimer = startTimer(animationInterval);
     } else {
         killTimer(m_animationTimer);
         m_animationTimer = 0;
     }
 }

 void CompositionRenderer::updateCirclePos()
 {
     if (m_current_object != NoObject)
         return;
     QDateTime dt = QDateTime::currentDateTime();
     qreal t = dt.toMSecsSinceEpoch() / 1000.0;

     qreal x = width() / qreal(2) + (qCos(t*8/11) + qSin(-t)) * width() / qreal(4);
     qreal y = height() / qreal(2) + (qSin(t*6/7) + qCos(t * qreal(1.5))) * height() / qreal(4);

     setCirclePos(QLineF(m_circle_pos, QPointF(x, y)).pointAt(0.02));
 }

 void CompositionRenderer::drawBase(QPainter &p)
 {
     p.setPen(Qt::NoPen);

     QLinearGradient rect_gradient(0, 0, 0, height());
     rect_gradient.setColorAt(0, Qt::red);
     rect_gradient.setColorAt(.17, Qt::yellow);
     rect_gradient.setColorAt(.33, Qt::green);
     rect_gradient.setColorAt(.50, Qt::cyan);
     rect_gradient.setColorAt(.66, Qt::blue);
     rect_gradient.setColorAt(.81, Qt::magenta);
     rect_gradient.setColorAt(1, Qt::red);
     p.setBrush(rect_gradient);
     p.drawRect(width() / 2, 0, width() / 2, height());

     QLinearGradient alpha_gradient(0, 0, width(), 0);
     alpha_gradient.setColorAt(0, Qt::white);
     alpha_gradient.setColorAt(0.2, Qt::white);
     alpha_gradient.setColorAt(0.5, Qt::transparent);
     alpha_gradient.setColorAt(0.8, Qt::white);
     alpha_gradient.setColorAt(1, Qt::white);

     p.setCompositionMode(QPainter::CompositionMode_DestinationIn);
     p.setBrush(alpha_gradient);
     p.drawRect(0, 0, width(), height());

     p.setCompositionMode(QPainter::CompositionMode_DestinationOver);

     p.setPen(Qt::NoPen);
     p.setRenderHint(QPainter::SmoothPixmapTransform);
     p.drawImage(rect(), m_image);
 }

 void CompositionRenderer::drawSource(QPainter &p)
 {
     p.setPen(Qt::NoPen);
     p.setRenderHint(QPainter::Antialiasing);
     p.setCompositionMode(m_composition_mode);

     QRectF circle_rect = rectangle_around(m_circle_pos);
     QColor color = QColor::fromHsvF(m_circle_hue / 360.0, 1, 1, m_circle_alpha / 255.0);
     QLinearGradient circle_gradient(circle_rect.topLeft(), circle_rect.bottomRight());
     circle_gradient.setColorAt(0, color.light());
     circle_gradient.setColorAt(0.5, color);
     circle_gradient.setColorAt(1, color.dark());
     p.setBrush(circle_gradient);

     p.drawEllipse(circle_rect);
 }

 void CompositionRenderer::paint(QPainter *painter)
 {
 #if QT_CONFIG(opengl)
     if (usesOpenGL() && glWindow()->isValid()) {

         if (!m_blitter.isCreated())
             m_blitter.create();

         int new_pbuf_size = m_pbuffer_size;
         while (size().width() > new_pbuf_size || size().height() > new_pbuf_size)
             new_pbuf_size *= 2;

         while (size().width() < new_pbuf_size/2 && size().height() < new_pbuf_size/2)
             new_pbuf_size /= 2;

         if (!m_fbo || new_pbuf_size != m_pbuffer_size) {
             m_fbo.reset(new QFboPaintDevice(QSize(new_pbuf_size, new_pbuf_size), false, false));
             m_pbuffer_size = new_pbuf_size;
         }

         if (size() != m_previous_size) {
             m_previous_size = size();
             QPainter p(m_fbo.data());
             p.setCompositionMode(QPainter::CompositionMode_Source);
             p.fillRect(QRect(QPoint(0, 0), size()), Qt::transparent);
             p.setCompositionMode(QPainter::CompositionMode_SourceOver);
             drawBase(p);
             p.end();
             m_base_tex = m_fbo->takeTexture();
         }

         painter->beginNativePainting();
         {
             QPainter p(m_fbo.data());
             p.beginNativePainting();
             m_blitter.bind();
             const QRect targetRect(QPoint(0, 0), m_fbo->size());
             const QMatrix4x4 target = QOpenGLTextureBlitter::targetTransform(targetRect, QRect(QPoint(0, 0), m_fbo->size()));
             m_blitter.blit(m_base_tex, target, QOpenGLTextureBlitter::OriginBottomLeft);
             m_blitter.release();
             p.endNativePainting();
             drawSource(p);
             p.end();
             m_compositing_tex = m_fbo->takeTexture();
         }
         painter->endNativePainting();

         painter->beginNativePainting();
         auto *funcs = QOpenGLContext::currentContext()->functions();
         funcs->glEnable(GL_BLEND);
         funcs->glBlendEquation(GL_FUNC_ADD);
         funcs->glBlendFunc(GL_ONE, GL_ONE_MINUS_SRC_ALPHA);
         m_blitter.bind();
         const QRect targetRect(QPoint(0, 0), m_fbo->size());
         const QMatrix4x4 target = QOpenGLTextureBlitter::targetTransform(targetRect, QRect(QPoint(0, 0), size()));
         m_blitter.blit(m_compositing_tex, target, QOpenGLTextureBlitter::OriginBottomLeft);
         m_blitter.release();
         painter->endNativePainting();
     } else
 #endif
     {
         // using a QImage
         if (m_buffer.size() != size()) {
             m_buffer = QImage(size(), QImage::Format_ARGB32_Premultiplied);
             m_base_buffer = QImage(size(), QImage::Format_ARGB32_Premultiplied);

             m_base_buffer.fill(0);

             QPainter p(&m_base_buffer);

             drawBase(p);
         }

         memcpy(m_buffer.bits(), m_base_buffer.bits(), m_buffer.sizeInBytes());

         {
             QPainter p(&m_buffer);
             drawSource(p);
         }

         painter->drawImage(0, 0, m_buffer);
     }
 }

 void CompositionRenderer::mousePressEvent(QMouseEvent *e)
 {
     setDescriptionEnabled(false);

     QRectF circle = rectangle_around(m_circle_pos);

     if (circle.contains(e->pos())) {
         m_current_object = Circle;
         m_offset = circle.center() - e->pos();
     } else {
         m_current_object = NoObject;
     }
     if (m_animation_enabled) {
         killTimer(m_animationTimer);
         m_animationTimer = 0;
     }
 }

 void CompositionRenderer::mouseMoveEvent(QMouseEvent *e)
 {
     if (m_current_object == Circle)
         setCirclePos(e->pos() + m_offset);
 }

 void CompositionRenderer::mouseReleaseEvent(QMouseEvent *)
 {
     m_current_object = NoObject;

     if (m_animation_enabled) {
         Q_ASSERT(!m_animationTimer);
         m_animationTimer = startTimer(animationInterval);
     }
 }

 void CompositionRenderer::timerEvent(QTimerEvent *event)
 {
     if (event->timerId() == m_animationTimer)
         updateCirclePos();
 }

 void CompositionRenderer::setCirclePos(const QPointF &pos)
 {
     const QRect oldRect = rectangle_around(m_circle_pos).toAlignedRect();
     m_circle_pos = pos;
     const QRect newRect = rectangle_around(m_circle_pos).toAlignedRect();
 #if QT_CONFIG(opengl)
     if (usesOpenGL()) {
         update();
         return;
     }
 #endif
     update(oldRect | newRect);
 }