paintarea.cpp Example File

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  #include "interfaces.h"
  #include "paintarea.h"

  #include <QMouseEvent>
  #include <QPainter>

  PaintArea::PaintArea(QWidget *parent) :
      QWidget(parent)
  {
      setAttribute(Qt::WA_StaticContents);
      setAttribute(Qt::WA_NoBackground);

      theImage.fill(qRgb(255, 255, 255));
  }

  bool PaintArea::openImage(const QString &fileName)
  {
      QImage image;
      if (!image.load(fileName))
          return false;

      setImage(image);
      return true;
  }

  bool PaintArea::saveImage(const QString &fileName, const char *fileFormat)
  {
      return theImage.save(fileName, fileFormat);
  }

  void PaintArea::setImage(const QImage &image)
  {
      theImage = image.convertToFormat(QImage::Format_RGB32);
      update();
      updateGeometry();
  }

  void PaintArea::insertShape(const QPainterPath &path)
  {
      pendingPath = path;
  #ifndef QT_NO_CURSOR
      setCursor(Qt::CrossCursor);
  #endif
  }

  void PaintArea::setBrushColor(const QColor &color)
  {
      this->color = color;
  }

  void PaintArea::setBrushWidth(int width)
  {
      thickness = width;
  }

  void PaintArea::setBrush(BrushInterface *brushInterface, const QString &brush)
  {
      this->brushInterface = brushInterface;
      this->brush = brush;
  }

  QSize PaintArea::sizeHint() const
  {
      return theImage.size();
  }

  void PaintArea::paintEvent(QPaintEvent * /* event */)
  {
      QPainter painter(this);
      painter.drawImage(QPoint(0, 0), theImage);
  }

  void PaintArea::mousePressEvent(QMouseEvent *event)
  {
      if (event->button() == Qt::LeftButton) {
          if (!pendingPath.isEmpty()) {
              QPainter painter(&theImage);
              setupPainter(painter);

              const QRectF boundingRect = pendingPath.boundingRect();
              QLinearGradient gradient(boundingRect.topRight(),
                                       boundingRect.bottomLeft());
              gradient.setColorAt(0.0, QColor(color.red(), color.green(),
                                              color.blue(), 63));
              gradient.setColorAt(1.0, QColor(color.red(), color.green(),
                                              color.blue(), 191));
              painter.setBrush(gradient);
              painter.translate(event->pos() - boundingRect.center());
              painter.drawPath(pendingPath);

              pendingPath = QPainterPath();
  #ifndef QT_NO_CURSOR
              unsetCursor();
  #endif
              update();
          } else {
              if (brushInterface) {
                  QPainter painter(&theImage);
                  setupPainter(painter);
                  const QRect rect = brushInterface->mousePress(brush, painter,
                                                                event->pos());
                  update(rect);
              }

              lastPos = event->pos();
          }
      }
  }

  void PaintArea::mouseMoveEvent(QMouseEvent *event)
  {
      if ((event->buttons() & Qt::LeftButton) && lastPos != QPoint(-1, -1)) {
          if (brushInterface) {
              QPainter painter(&theImage);
              setupPainter(painter);
              const QRect rect = brushInterface->mouseMove(brush, painter, lastPos,
                                                           event->pos());
              update(rect);
          }

          lastPos = event->pos();
      }
  }

  void PaintArea::mouseReleaseEvent(QMouseEvent *event)
  {
      if (event->button() == Qt::LeftButton && lastPos != QPoint(-1, -1)) {
          if (brushInterface) {
              QPainter painter(&theImage);
              setupPainter(painter);
              QRect rect = brushInterface->mouseRelease(brush, painter,
                                                        event->pos());
              update(rect);
          }

          lastPos = QPoint(-1, -1);
      }
  }

  void PaintArea::setupPainter(QPainter &painter)
  {
      painter.setRenderHint(QPainter::Antialiasing, true);
      painter.setPen(QPen(color, thickness, Qt::SolidLine, Qt::RoundCap,
                     Qt::RoundJoin));
  }