imagewidget.cpp Example File
gestures/imagegestures/imagewidget.cpp
#include "imagewidget.h"
#include <QtWidgets>
Q_LOGGING_CATEGORY(lcExample, "qt.examples.imagegestures")
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();
qCDebug(lcExample) << "reset on mouse double click";
}
bool ImageWidget::gestureEvent(QGestureEvent *event)
{
qCDebug(lcExample) << "gestureEvent():" << event;
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();
qCDebug(lcExample) << "panTriggered():" << gesture;
horizontalOffset += delta.x();
verticalOffset += delta.y();
update();
}
void ImageWidget::pinchTriggered(QPinchGesture *gesture)
{
QPinchGesture::ChangeFlags changeFlags = gesture->changeFlags();
if (changeFlags & QPinchGesture::RotationAngleChanged) {
qreal rotationDelta = gesture->rotationAngle() - gesture->lastRotationAngle();
rotationAngle += rotationDelta;
qCDebug(lcExample) << "pinchTriggered(): rotate by" <<
rotationDelta << "->" << rotationAngle;
}
if (changeFlags & QPinchGesture::ScaleFactorChanged) {
currentStepScaleFactor = gesture->totalScaleFactor();
qCDebug(lcExample) << "pinchTriggered(): zoom by" <<
gesture->scaleFactor() << "->" << 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) {
qCDebug(lcExample) << "swipeTriggered(): swipe to previous";
goPrevImage();
} else {
qCDebug(lcExample) << "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)
{
QImageReader reader(fileName);
reader.setAutoTransform(true);
qCDebug(lcExample) << "loading" << QDir::toNativeSeparators(fileName) << position << '/' << files.size();
if (!reader.canRead()) {
qCWarning(lcExample) << QDir::toNativeSeparators(fileName) << ": can't load image";
return QImage();
}
QImage image;
if (!reader.read(&image)) {
qCWarning(lcExample) << QDir::toNativeSeparators(fileName) << ": corrupted image: " << reader.errorString();
return QImage();
}
const QSize maximumSize(2000, 2000);
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 + QLatin1Char('/') + 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 + QLatin1Char('/') + files.at(position-1));
else
prevImage = QImage();
}
update();
}
void ImageWidget::goToImage(int index)
{
if (files.isEmpty())
return;
if (index < 0 || index >= files.size()) {
qCWarning(lcExample) << "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 + QLatin1Char('/') + files.at(position-1));
else
prevImage = QImage();
currentImage = loadImage(path + QLatin1Char('/') + files.at(position));
if (position+1 < files.size())
nextImage = loadImage(path + QLatin1Char('/') + files.at(position+1));
else
nextImage = QImage();
update();
}