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.
 **
 ** $QT_BEGIN_LICENSE:BSD$
 ** You may use this file under the terms of the BSD license as follows:
 **
 ** "Redistribution and use in source and binary forms, with or without
 ** modification, are permitted provided that the following conditions are
 ** met:
 **   * Redistributions of source code must retain the above copyright
 **     notice, this list of conditions and the following disclaimer.
 **   * Redistributions in binary form must reproduce the above copyright
 **     notice, this list of conditions and the following disclaimer in
 **     the documentation and/or other materials provided with the
 **     distribution.
 **   * Neither the name of The Qt Company Ltd nor the names of its
 **     contributors may be used to endorse or promote products derived
 **     from this software without specific prior written permission.
 **
 **
 ** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 ** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 ** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 ** A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 ** OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 ** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 ** LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 ** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 ** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 ** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 ** OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE."
 **
 ** $QT_END_LICENSE$
 **
 ****************************************************************************/

 #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();
 }