QT Thumbnails Dyamically

[amarism]

I want to create Thumbnails(a group of an image) inside the ListWidget to select multiple images and have to display images one by one inside the Widget box using button click.

[Taz742]

@amarism Hi.
What are you tried ? What is problem?

[amarism]

This post is deleted!

[mrjj]

Hi
You can use
http://doc.qt.io/qt-5/qimage.html with
http://doc.qt.io/qt-5/qimage.html#scaled
to produce the thumbnails

You can use something like

//assume the directory exists and contains some files and you want all jpg and JPG files
QDir directory("Pictures/MyPictures");
QStringList images = directory.entryList(QStringList() << "*.jpg" << "*.JPG",QDir::Files);
foreach(QString filename, images) {
//do whatever you need to do
}
(thx to @the_ )
```.
To grab all files from a folder to produce the thumbnails,

- images one by one inside the Widget box 

I dont know what widgetbox is, but you can use QScrollArea 
http://doc.qt.io/qt-5/qscrollarea.html
if you need any kinda of scrolling.

[amarism]

@Taz742 I tried to make a thumbnail inside ListWidget that select image from my computer dynamically. I will make a code for static but I need a dynamic image selection code.
This is static image selection code.
ui->setupUi(this);
ui->listWidget->setViewMode(QListWidget::IconMode);
ui->listWidget->setIconSize(QSize(130,130));
ui->listWidget->setResizeMode(QListWidget::Adjust);
ui->listWidget->addItem(new QListWidgetItem(QIcon("D:/qt_pic/LoginRed.jpg"),"logo"));
ui->listWidget->addItem(new QListWidgetItem(QIcon("D:/qt_pic/1234.jpg"),"wallpaper"));
ui->listWidget->addItem(new QListWidgetItem(QIcon("D:/qt_pic/4321.jpg"),"eye"));
ui->listWidget->addItem(new QListWidgetItem(QIcon("D:/qt_pic/dog.jpg"),"Dog"));

[mrjj]

Hi
So you need all files from a given folder or you need to let user
select images one by one ?

[amarism]

@mrjj User select image one by one

[mrjj]

@amarism
Ok. you can use normal QFileOpenDialog
https://doc.qt.io/qt-5/qfiledialog.html#getOpenFileName
to let user do that.

[Taz742]

@mrjj + something like this:
.h

private:
    Ui::MainWindow*ui; 
    QMap<QString, QListWidgetItem*> m_mapFileNameListWidgetItem;

.cpp

void MainWindow::on_btnChooseImage_clicked()
{
    QDir dr;
    QStringList list = QFileDialog::getOpenFileNames(this, QString("Choose Images"), dr.absolutePath(), tr("Format (*.png *.jpg *.jpeg))"));
    if (list.empty())
        return;
    startThread(list);
}


void MainWindow::startThread(QStringList list)
{
    for (QString str : list) {
        if (m_mapFileNameListWidgetItem.find(str) != m_mapFileNameListWidgetItem.end())
            continue;

        QListWidgetItem *item = new QListWidgetItem(ui->listWidget);
        item->setSizeHint(QSize(150, 150);
        ui->listWidget->addItem(item);
        m_mapFileNameListWidgetItem[str] = item;

        QRunnableForImage *sub = new QRunnableForImage(str);
        connect(sub, SIGNAL(finished(QString, QImage, QByteArray)), this, SLOT(imageLoaded(QString, QImage, QByteArray)), Qt::QueuedConnection);
        QThreadPool::globalInstance()->start(sub);
    }
}


void MainWindow::imageLoaded(QString fileName, QImage img130x130, QByteArray bytes)
{
    QListWidgetItem *item = m_mapFileNameListWidgetItem[fileName];
    if (!item) {
        return;
    }
    item->setIcon(QIcon(QPixmap::fromImage(img130x130)));
}

QRunnable .h

#ifndef QRUNNABLEFORIMAGE_H
#define QRUNNABLEFORIMAGE_H

#include <QObject>
#include "QRunnable"
#include "QFile"
#include "QImage"
#include "QDebug"

class QRunnableForImage : public QObject, public QRunnable
{
    Q_OBJECT
public:
    explicit QRunnableForImage(QString fileName, QObject *parent = 0);

    ~QRunnableForImage() {
        qDebug() << "qrunnableforimage deleted";
    }

signals:
    void finished(QString filename, QImage img130x130, QByteArray bytes);
    void errorFound(QString what);

public slots:
    void run();

private:
    QString fileName;
};

#endif // QRUNNABLEFORIMAGE_H

.cpp

#include "qrunnableforimage.h"
#include "QBuffer"

QRunnableForImage::QRunnableForImage(QString fileName, QObject *parent) : QObject(parent)
{
    this->fileName = fileName;
}

void QRunnableForImage::run()
{
    QFile fl(this->fileName);
    if (fl.open(QIODevice::ReadOnly)) {
        QByteArray bytes = fl.readAll();

        QImage img130x130;
        img130x130= img130x130.fromData(bytes);
        img130x130= img130x130.scaled(130, 130, Qt::IgnoreAspectRatio, Qt::SmoothTransformation);

        emit finished(this->fileName, img130x130, bytes);
    } else {
        emit errorFound(fl.errorString());
    }
}

[mrjj]

@Taz742
Cool. a threaded image loader :)