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# imagewidget.cpp Example File

gestures/imagegestures/imagewidget.cpp

     /****************************************************************************
     **
     ** Copyright (C) 2015 The Qt Company Ltd.
     ** Contact: http://www.qt.io/licensing/
     **
     ** This file is part of the examples of the Qt Toolkit.
     **
     ** $QT_BEGIN_LICENSE:BSD$
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     **
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     ** modification, are permitted provided that the following conditions are
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     **     from this software without specific prior written permission.
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     #include "imagewidget.h"

     #include <QtGui>

     bool ImageWidget::verbose = false;

     ImageWidget::ImageWidget(QWidget *parent)
         : QWidget(parent),
         position(0),
         horizontalOffset(0),
         verticalOffset(0),
         rotationAngle(0),
         scaleFactor(1),
         currentStepScaleFactor(1)

     {
         setMinimumSize(QSize(100,100));
     }

     void ImageWidget::grabGestures(const QList<Qt::GestureType> &gestures)
     {
         foreach (Qt::GestureType gesture, gestures)
             grabGesture(gesture);
     }

     bool ImageWidget::event(QEvent *event)
     {
         if (event->type() == QEvent::Gesture)
             return gestureEvent(static_cast<QGestureEvent*>(event));
         return QWidget::event(event);
     }

     void ImageWidget::paintEvent(QPaintEvent*)
     {
         QPainter p(this);

         const qreal iw = currentImage.width();
         const qreal ih = currentImage.height();
         const qreal wh = height();
         const qreal ww = width();

         p.translate(ww/2, wh/2);
         p.translate(horizontalOffset, verticalOffset);
         p.rotate(rotationAngle);
         p.scale(currentStepScaleFactor * scaleFactor, currentStepScaleFactor * scaleFactor);
         p.translate(-iw/2, -ih/2);
         p.drawImage(0, 0, currentImage);
     }

     void ImageWidget::mouseDoubleClickEvent(QMouseEvent *)
     {
         rotationAngle = 0;
         scaleFactor = 1;
         currentStepScaleFactor = 1;
         verticalOffset = 0;
         horizontalOffset = 0;
         update();
         if (ImageWidget::verbose)
             qDebug() << "reset on mouse double click";
     }

     bool ImageWidget::gestureEvent(QGestureEvent *event)
     {
         if (ImageWidget::verbose)
             qDebug() << "gestureEvent():" << event->gestures().size();
         if (QGesture *swipe = event->gesture(Qt::SwipeGesture))
             swipeTriggered(static_cast<QSwipeGesture *>(swipe));
         else if (QGesture *pan = event->gesture(Qt::PanGesture))
             panTriggered(static_cast<QPanGesture *>(pan));
         if (QGesture *pinch = event->gesture(Qt::PinchGesture))
             pinchTriggered(static_cast<QPinchGesture *>(pinch));
         return true;
     }

     void ImageWidget::panTriggered(QPanGesture *gesture)
     {
     #ifndef QT_NO_CURSOR
         switch (gesture->state()) {
             case Qt::GestureStarted:
             case Qt::GestureUpdated:
                 setCursor(Qt::SizeAllCursor);
                 break;
             default:
                 setCursor(Qt::ArrowCursor);
         }
     #endif
         QPointF delta = gesture->delta();
         if (ImageWidget::verbose)
             qDebug() << "panTriggered():" << delta;
         horizontalOffset += delta.x();
         verticalOffset += delta.y();
         update();
     }

     void ImageWidget::pinchTriggered(QPinchGesture *gesture)
     {
         QPinchGesture::ChangeFlags changeFlags = gesture->changeFlags();
         if (changeFlags & QPinchGesture::RotationAngleChanged) {
             const qreal value = gesture->property("rotationAngle").toReal();
             const qreal lastValue = gesture->property("lastRotationAngle").toReal();
             const qreal rotationAngleDelta = value - lastValue;
             rotationAngle += rotationAngleDelta;
             if (ImageWidget::verbose)
                 qDebug() << "pinchTriggered(): rotation by" << rotationAngleDelta << rotationAngle;
         }
         if (changeFlags & QPinchGesture::ScaleFactorChanged) {
             qreal value = gesture->property("scaleFactor").toReal();
             currentStepScaleFactor = value;
             if (ImageWidget::verbose)
                 qDebug() << "pinchTriggered(): " << currentStepScaleFactor;
         }
         if (gesture->state() == Qt::GestureFinished) {
             scaleFactor *= currentStepScaleFactor;
             currentStepScaleFactor = 1;
         }
         update();
     }

     void ImageWidget::swipeTriggered(QSwipeGesture *gesture)
     {
         if (gesture->state() == Qt::GestureFinished) {
             if (gesture->horizontalDirection() == QSwipeGesture::Left
                 || gesture->verticalDirection() == QSwipeGesture::Up) {
                 if (ImageWidget::verbose)
                     qDebug() << "swipeTriggered(): swipe to previous";
                 goPrevImage();
             } else {
                 if (ImageWidget::verbose)
                     qDebug() << "swipeTriggered(): swipe to next";
                 goNextImage();
             }
             update();
         }
     }

     void ImageWidget::resizeEvent(QResizeEvent*)
     {
         update();
     }

     void ImageWidget::openDirectory(const QString &path)
     {
         this->path = path;
         QDir dir(path);
         QStringList nameFilters;
         nameFilters << "*.jpg" << "*.png";
         files = dir.entryList(nameFilters, QDir::Files|QDir::Readable, QDir::Name);

         position = 0;
         goToImage(0);
         update();
     }

     QImage ImageWidget::loadImage(const QString &fileName)
     {
         qDebug() << position << files << fileName;
         QImageReader reader(fileName);
         if (ImageWidget::verbose)
             qDebug() << "loading" << QDir::toNativeSeparators(fileName) << position << '/' << files.size();
         if (!reader.canRead()) {
             qWarning() << QDir::toNativeSeparators(fileName) << ": can't load image";
             return QImage();
         }

         QImage image;
         if (!reader.read(&image)) {
             qWarning() << QDir::toNativeSeparators(fileName) << ": corrupted image: " << reader.errorString();
             return QImage();
         }
         const QSize maximumSize(2000, 2000); // Reduce in case someone has large photo images.
         if (image.size().width() > maximumSize.width() || image.height() > maximumSize.height())
             image = image.scaled(maximumSize, Qt::KeepAspectRatio, Qt::SmoothTransformation);
         return image;
     }

     void ImageWidget::goNextImage()
     {
         if (files.isEmpty())
             return;

         if (position < files.size()-1) {
             ++position;
             prevImage = currentImage;
             currentImage = nextImage;
             if (position+1 < files.size())
                 nextImage = loadImage(path+QLatin1String("/")+files.at(position+1));
             else
                 nextImage = QImage();
         }
         update();
     }

     void ImageWidget::goPrevImage()
     {
         if (files.isEmpty())
             return;

         if (position > 0) {
             --position;
             nextImage = currentImage;
             currentImage = prevImage;
             if (position > 0)
                 prevImage = loadImage(path+QLatin1String("/")+files.at(position-1));
             else
                 prevImage = QImage();
         }
         update();
     }

     void ImageWidget::goToImage(int index)
     {
         if (files.isEmpty())
             return;

         if (index < 0 || index >= files.size()) {
             qWarning() << "goToImage: invalid index: " << index;
             return;
         }

         if (index == position+1) {
             goNextImage();
             return;
         }

         if (position > 0 && index == position-1) {
             goPrevImage();
             return;
         }

         position = index;

         if (index > 0)
             prevImage = loadImage(path+QLatin1String("/")+files.at(position-1));
         else
             prevImage = QImage();
         currentImage = loadImage(path+QLatin1String("/")+files.at(position));
         if (position+1 < files.size())
             nextImage = loadImage(path+QLatin1String("/")+files.at(position+1));
         else
             nextImage = QImage();
         update();
     }