Qt Reference Documentation

# scribblearea.cpp Example File

touch/fingerpaint/scribblearea.cpp

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     ** This file is part of the examples of the Qt Toolkit.
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     #include <QtGui>

     #include "scribblearea.h"

     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()
     {
     #ifndef QT_NO_PRINTER
         QPrinter printer(QPrinter::HighResolution);

         QPrintDialog *printDialog = new QPrintDialog(&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
     }

     bool ScribbleArea::event(QEvent *event)
     {
         switch (event->type()) {
         case QEvent::TouchBegin:
         case QEvent::TouchUpdate:
         case QEvent::TouchEnd:
         {
             QList<QTouchEvent::TouchPoint> touchPoints = static_cast<QTouchEvent *>(event)->touchPoints();
             foreach (const QTouchEvent::TouchPoint &touchPoint, touchPoints) {
                 switch (touchPoint.state()) {
                 case Qt::TouchPointStationary:
                     // don't do anything if this touch point hasn't moved
                     continue;
                 default:
                     {
                         QRectF rect = touchPoint.rect();
                         if (rect.isEmpty()) {
                             qreal diameter = qreal(50) * touchPoint.pressure();
                             QPointF center = rect.center();
                             rect.setSize(QSizeF(diameter, diameter));
                             rect.moveCenter(center);
                         }

                         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;
     }