imagescaling.cpp Example File

imagescaling/imagescaling.cpp
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#include "imagescaling.h" #include <qmath.h> #include <functional> Images::Images(QWidget *parent) : QWidget(parent) { setWindowTitle(tr("Image loading and scaling example")); resize(800, 600); imageScaling = new QFutureWatcher<QImage>(this); connect(imageScaling, &QFutureWatcher<QImage>::resultReadyAt, this, &Images::showImage); connect(imageScaling, &QFutureWatcher<QImage>::finished, this, &Images::finished); openButton = new QPushButton(tr("Open Images")); connect(openButton, &QPushButton::clicked, this, &Images::open); cancelButton = new QPushButton(tr("Cancel")); cancelButton->setEnabled(false); connect(cancelButton, &QPushButton::clicked, imageScaling, &QFutureWatcher<QImage>::cancel); pauseButton = new QPushButton(tr("Pause/Resume")); pauseButton->setEnabled(false); connect(pauseButton, &QPushButton::clicked, imageScaling, &QFutureWatcher<QImage>::togglePaused); QHBoxLayout *buttonLayout = new QHBoxLayout(); buttonLayout->addWidget(openButton); buttonLayout->addWidget(cancelButton); buttonLayout->addWidget(pauseButton); buttonLayout->addStretch(); imagesLayout = new QGridLayout(); mainLayout = new QVBoxLayout(); mainLayout->addLayout(buttonLayout); mainLayout->addLayout(imagesLayout); mainLayout->addStretch(); setLayout(mainLayout); } Images::~Images() { imageScaling->cancel(); imageScaling->waitForFinished(); } void Images::open() { // Cancel and wait if we are already loading images. if (imageScaling->isRunning()) { imageScaling->cancel(); imageScaling->waitForFinished(); } // Show a file open dialog at QStandardPaths::PicturesLocation. QStringList files = QFileDialog::getOpenFileNames(this, tr("Select Images"), QStandardPaths::writableLocation(QStandardPaths::PicturesLocation), "*.jpg *.png"); if (files.isEmpty()) return; const int imageSize = 100; // Do a simple layout. qDeleteAll(labels); labels.clear(); int dim = qSqrt(qreal(files.count())) + 1; for (int i = 0; i < dim; ++i) { for (int j = 0; j < dim; ++j) { QLabel *imageLabel = new QLabel; imageLabel->setFixedSize(imageSize,imageSize); imagesLayout->addWidget(imageLabel,i,j); labels.append(imageLabel); } } std::function<QImage(const QString&)> scale = [imageSize](const QString &imageFileName) { QImage image(imageFileName); return image.scaled(QSize(imageSize, imageSize), Qt::IgnoreAspectRatio, Qt::SmoothTransformation); }; // Use mapped to run the thread safe scale function on the files. imageScaling->setFuture(QtConcurrent::mapped(files, scale)); openButton->setEnabled(false); cancelButton->setEnabled(true); pauseButton->setEnabled(true); } void Images::showImage(int num) { labels[num]->setPixmap(QPixmap::fromImage(imageScaling->resultAt(num))); } void Images::finished() { openButton->setEnabled(true); cancelButton->setEnabled(false); pauseButton->setEnabled(false); }