imagecomposer.cpp Example File

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  #include "imagecomposer.h"

  #include <QtWidgets>

  static const QSize resultSize(200, 200);

  ImageComposer::ImageComposer()
  {
      sourceButton = new QToolButton;
      sourceButton->setIconSize(resultSize);

      operatorComboBox = new QComboBox;
      addOp(QPainter::CompositionMode_SourceOver, tr("SourceOver"));
      addOp(QPainter::CompositionMode_DestinationOver, tr("DestinationOver"));
      addOp(QPainter::CompositionMode_Clear, tr("Clear"));
      addOp(QPainter::CompositionMode_Source, tr("Source"));
      addOp(QPainter::CompositionMode_Destination, tr("Destination"));
      addOp(QPainter::CompositionMode_SourceIn, tr("SourceIn"));
      addOp(QPainter::CompositionMode_DestinationIn, tr("DestinationIn"));
      addOp(QPainter::CompositionMode_SourceOut, tr("SourceOut"));
      addOp(QPainter::CompositionMode_DestinationOut, tr("DestinationOut"));
      addOp(QPainter::CompositionMode_SourceAtop, tr("SourceAtop"));
      addOp(QPainter::CompositionMode_DestinationAtop, tr("DestinationAtop"));
      addOp(QPainter::CompositionMode_Xor, tr("Xor"));
      addOp(QPainter::CompositionMode_Plus, tr("Plus"));
      addOp(QPainter::CompositionMode_Multiply, tr("Multiply"));
      addOp(QPainter::CompositionMode_Screen, tr("Screen"));
      addOp(QPainter::CompositionMode_Overlay, tr("Overlay"));
      addOp(QPainter::CompositionMode_Darken, tr("Darken"));
      addOp(QPainter::CompositionMode_Lighten, tr("Lighten"));
      addOp(QPainter::CompositionMode_ColorDodge, tr("ColorDodge"));
      addOp(QPainter::CompositionMode_ColorBurn, tr("ColorBurn"));
      addOp(QPainter::CompositionMode_HardLight, tr("HardLight"));
      addOp(QPainter::CompositionMode_SoftLight, tr("SoftLight"));
      addOp(QPainter::CompositionMode_Difference, tr("Difference"));
      addOp(QPainter::CompositionMode_Exclusion, tr("Exclusion"));

      destinationButton = new QToolButton;
      destinationButton->setIconSize(resultSize);

      equalLabel = new QLabel(tr("="));

      resultLabel = new QLabel;
      resultLabel->setMinimumWidth(resultSize.width());

      connect(sourceButton, SIGNAL(clicked()), this, SLOT(chooseSource()));
      connect(operatorComboBox, SIGNAL(activated(int)), this, SLOT(recalculateResult()));
      connect(destinationButton, SIGNAL(clicked()), this, SLOT(chooseDestination()));

      QGridLayout *mainLayout = new QGridLayout;
      mainLayout->addWidget(sourceButton, 0, 0, 3, 1);
      mainLayout->addWidget(operatorComboBox, 1, 1);
      mainLayout->addWidget(destinationButton, 0, 2, 3, 1);
      mainLayout->addWidget(equalLabel, 1, 3);
      mainLayout->addWidget(resultLabel, 0, 4, 3, 1);
      mainLayout->setSizeConstraint(QLayout::SetFixedSize);
      setLayout(mainLayout);

      resultImage = QImage(resultSize, QImage::Format_ARGB32_Premultiplied);

      loadImage(":/images/butterfly.png", &sourceImage, sourceButton);
      loadImage(":/images/checker.png", &destinationImage, destinationButton);

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

  void ImageComposer::chooseSource()
  {
      chooseImage(tr("Choose Source Image"), &sourceImage, sourceButton);
  }

  void ImageComposer::chooseDestination()
  {
      chooseImage(tr("Choose Destination Image"), &destinationImage, destinationButton);
  }

  void ImageComposer::recalculateResult()
  {
      QPainter::CompositionMode mode = currentMode();

      QPainter painter(&resultImage);
      painter.setCompositionMode(QPainter::CompositionMode_Source);
      painter.fillRect(resultImage.rect(), Qt::transparent);
      painter.setCompositionMode(QPainter::CompositionMode_SourceOver);
      painter.drawImage(0, 0, destinationImage);
      painter.setCompositionMode(mode);
      painter.drawImage(0, 0, sourceImage);
      painter.setCompositionMode(QPainter::CompositionMode_DestinationOver);
      painter.fillRect(resultImage.rect(), Qt::white);
      painter.end();

      resultLabel->setPixmap(QPixmap::fromImage(resultImage));
  }

  void ImageComposer::addOp(QPainter::CompositionMode mode, const QString &name)
  {
      operatorComboBox->addItem(name, mode);
  }

  void ImageComposer::chooseImage(const QString &title, QImage *image,
                                  QToolButton *button)
  {
      QString fileName = QFileDialog::getOpenFileName(this, title);
      if (!fileName.isEmpty())
          loadImage(fileName, image, button);
  }

  void ImageComposer::loadImage(const QString &fileName, QImage *image,
                                QToolButton *button)
  {
      image->load(fileName);

      // Scale the image to given size
      *image = image->scaled(resultSize, Qt::KeepAspectRatio);

      QImage fixedImage(resultSize, QImage::Format_ARGB32_Premultiplied);
      QPainter painter(&fixedImage);
      painter.setCompositionMode(QPainter::CompositionMode_Source);
      painter.fillRect(fixedImage.rect(), Qt::transparent);
      painter.setCompositionMode(QPainter::CompositionMode_SourceOver);
      painter.drawImage(imagePos(*image), *image);
      painter.end();
      button->setIcon(QPixmap::fromImage(fixedImage));

      *image = fixedImage;

      recalculateResult();
  }

  QPainter::CompositionMode ImageComposer::currentMode() const
  {
      return (QPainter::CompositionMode)
             operatorComboBox->itemData(operatorComboBox->currentIndex()).toInt();
  }

  QPoint ImageComposer::imagePos(const QImage &image) const
  {
      return QPoint((resultSize.width() - image.width()) / 2,
                    (resultSize.height() - image.height()) / 2);
  }