Show image in a column of QTableView from QSqlTableModel

Question

I'm curious about how I can display an image from my database in a QTableView.

Is there something like QTableWidgetItem that I am able to use it in QTableView?

I use QSqlTableModel.

Answer 1

A rough idea is to use QStandardItem::setData to set a QPixmap(transformed into QVariant) on it, then you can set the QStandardItem on the QStandardItemModel.

Sequence: QImage--->QPixmap--->QVariant--->QStandardItem--->QStandardItemModel

For example:

QStandardItemModel *model = new QStandardItemModel;
QImage image(":/cat/lovers/own/myCat.jpg");
QStandardItem *item = new QStandardItem();
item->setData(QVariant(QPixmap::fromImage(image)), Qt::DecorationRole);
model->setItem(0, 0, item);
ui->tableView->setModel(model);

You will have to resize images or cell size, depends on what you need.

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[Edit]

If you are using QSqlTableModel, just keep using it. All we need to do is make those path strings into QPixmap and set the item role to be Qt::DecorationRole in that column.

As the document says:

Each item has a number of data elements associated with it and they can be retrieved by specifying a role (see Qt::ItemDataRole) to the model's data() function.

To do this, the concept is simple: provide QTableView with QVariant of QPixmap as QTableView render them according to Qt::DecorationRole.

You may subclass QSqlTableModel and reimplement the virtual function QVariant data(const QModelIndex & index, int role = Qt::DisplayRole) and make the image column return the QPixmap as QVariant, with the decoration role. So do something like this:

QVariant CustomSqlTableModel::data(const QModelIndex &idx, int role = Qt::DisplayRole) const
{
     if (idx.column() == imageColumn) {
         QString imgFile = QSqlTableModel::data(idx, Qt::DisplayRole); // get path string

        if (role == Qt::DisplayRole) 
            return QString(); // return the path string for display role

        QImage image(imgFile);
        /* some modification to the image, maybe */

        QPixmap pixmap(imgFile);
        if (role == Qt::DecorationRole)
            return pixmap;   // return QPixmap for decoration role

        if (role == Qt::SizeHintRole)
            return pixmap.size(); // in case need the image size

     }
     return QSqlTableModel::data( idx, role ); // use original data() outside the imageColumn
}

Besides, you can also try subclassing QStyledItemDelegate and reimplement paint() function to customize your own delegate, but that will require a more complicated work. An example using delegate can be found here. You can paint whatever you want with delegate, even a button.

*Sorry the code is not tested, as I don't have a database on hand.