scribblearea.cpp Example File

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  #include <QtWidgets>
  #ifndef QT_NO_PRINTER
  #include <QPrinter>
  #include <QPrintDialog>
  #endif

  #include "scribblearea.h"

  ScribbleArea::ScribbleArea(QWidget *parent)
      : QWidget(parent)
  {
      setAttribute(Qt::WA_StaticContents);
      modified = false;
      scribbling = false;
      myPenWidth = 1;
      myPenColor = Qt::blue;
  }

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

      QSize newSize = loadedImage.size().expandedTo(size());
      resizeImage(&loadedImage, newSize);
      image = loadedImage;
      modified = false;
      update();
      return true;
  }

  bool ScribbleArea::saveImage(const QString &fileName, const char *fileFormat)
  {
      QImage visibleImage = image;
      resizeImage(&visibleImage, size());

      if (visibleImage.save(fileName, fileFormat)) {
          modified = false;
          return true;
      } else {
          return false;
      }
  }

  void ScribbleArea::setPenColor(const QColor &newColor)
  {
      myPenColor = newColor;
  }

  void ScribbleArea::setPenWidth(int newWidth)
  {
      myPenWidth = newWidth;
  }

  void ScribbleArea::clearImage()
  {
      image.fill(qRgb(255, 255, 255));
      modified = true;
      update();
  }

  void ScribbleArea::mousePressEvent(QMouseEvent *event)
  {
      if (event->button() == Qt::LeftButton) {
          lastPoint = event->pos();
          scribbling = true;
      }
  }

  void ScribbleArea::mouseMoveEvent(QMouseEvent *event)
  {
      if ((event->buttons() & Qt::LeftButton) && scribbling)
          drawLineTo(event->pos());
  }

  void ScribbleArea::mouseReleaseEvent(QMouseEvent *event)
  {
      if (event->button() == Qt::LeftButton && scribbling) {
          drawLineTo(event->pos());
          scribbling = false;
      }
  }

  void ScribbleArea::paintEvent(QPaintEvent *event)
  {
      QPainter painter(this);
      QRect dirtyRect = event->rect();
      painter.drawImage(dirtyRect, image, dirtyRect);
  }

  void ScribbleArea::resizeEvent(QResizeEvent *event)
  {
      if (width() > image.width() || height() > image.height()) {
          int newWidth = qMax(width() + 128, image.width());
          int newHeight = qMax(height() + 128, image.height());
          resizeImage(&image, QSize(newWidth, newHeight));
          update();
      }
      QWidget::resizeEvent(event);
  }

  void ScribbleArea::drawLineTo(const QPoint &endPoint)
  {
      QPainter painter(&image);
      painter.setPen(QPen(myPenColor, myPenWidth, Qt::SolidLine, Qt::RoundCap,
                          Qt::RoundJoin));
      painter.drawLine(lastPoint, endPoint);
      modified = true;

      int rad = (myPenWidth / 2) + 2;
      update(QRect(lastPoint, endPoint).normalized()
                                       .adjusted(-rad, -rad, +rad, +rad));
      lastPoint = endPoint;
  }

  void ScribbleArea::resizeImage(QImage *image, const QSize &newSize)
  {
      if (image->size() == newSize)
          return;

      QImage newImage(newSize, QImage::Format_RGB32);
      newImage.fill(qRgb(255, 255, 255));
      QPainter painter(&newImage);
      painter.drawImage(QPoint(0, 0), *image);
      *image = newImage;
  }

  void ScribbleArea::print()
  {
  #if !defined(QT_NO_PRINTER) && !defined(QT_NO_PRINTDIALOG)
      QPrinter printer(QPrinter::HighResolution);

      QPrintDialog printDialog(&printer, this);
      if (printDialog.exec() == QDialog::Accepted) {
          QPainter painter(&printer);
          QRect rect = painter.viewport();
          QSize size = image.size();
          size.scale(rect.size(), Qt::KeepAspectRatio);
          painter.setViewport(rect.x(), rect.y(), size.width(), size.height());
          painter.setWindow(image.rect());
          painter.drawImage(0, 0, image);
      }
  #endif // QT_NO_PRINTER
  }