scribblearea.cpp Example File

touch/fingerpaint/scribblearea.cpp

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  #include <QtWidgets>
  #if defined(QT_PRINTSUPPORT_LIB)
  #include <QtPrintSupport/qtprintsupportglobal.h>
  #if QT_CONFIG(printdialog)
  #include <QPrinter>
  #include <QPrintDialog>
  #endif
  #endif

  #include "scribblearea.h"

  static const qreal MinimumDiameter = 3.0;
  static const qreal MaximumDiameter = 50.0;

  ScribbleArea::ScribbleArea(QWidget *parent)
      : QWidget(parent)
  {
      setAttribute(Qt::WA_AcceptTouchEvents);
      setAttribute(Qt::WA_StaticContents);
      modified = false;

      myPenColors
              << QColor("green")
              << QColor("purple")
              << QColor("red")
              << QColor("blue")
              << QColor("yellow")

              << QColor("pink")
              << QColor("orange")
              << QColor("brown")
              << QColor("grey")
              << QColor("black");
  }

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

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

  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::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 QT_CONFIG(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_CONFIG(printdialog)
  }

  bool ScribbleArea::event(QEvent *event)
  {
      switch (event->type()) {
      case QEvent::TouchBegin:
      case QEvent::TouchUpdate:
      case QEvent::TouchEnd:
      {
          QTouchEvent *touch = static_cast<QTouchEvent *>(event);
          QList<QTouchEvent::TouchPoint> touchPoints = static_cast<QTouchEvent *>(event)->touchPoints();
          foreach (const QTouchEvent::TouchPoint &touchPoint, touchPoints) {
              switch (touchPoint.state()) {
              case Qt::TouchPointStationary:
              case Qt::TouchPointReleased:
                  // don't do anything if this touch point hasn't moved or has been released
                  continue;
              default:
                  {
                      QRectF rect = touchPoint.rect();
                      if (rect.isEmpty()) {
                          qreal diameter = MaximumDiameter;
                          if (touch->device()->capabilities() & QTouchDevice::Pressure)
                              diameter = MinimumDiameter + (MaximumDiameter - MinimumDiameter) * touchPoint.pressure();
                          rect.setSize(QSizeF(diameter, diameter));
                      }

                      QPainter painter(&image);
                      painter.setPen(Qt::NoPen);
                      painter.setBrush(myPenColors.at(touchPoint.id() % myPenColors.count()));
                      painter.drawEllipse(rect);
                      painter.end();

                      modified = true;
                      int rad = 2;
                      update(rect.toRect().adjusted(-rad,-rad, +rad, +rad));
                  }
                  break;
              }
          }
          break;
      }
      default:
          return QWidget::event(event);
      }
      return true;
  }