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.

Bursar

You could look at QAbstractItemModel::data() in combination with Qt::DecorationRole. – Diorite

What's the form of your database? Is that a bunch of paths of images? – Selfannihilation

yes it's a path, but does it make difference if I store image as BOLB? – Bursar

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.

---

[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.

Selfannihilation

How I should use QStandardItemModel with QSqlTableModel? – Bursar

@Bursar You should've said that you are using QSqlTableModel in the question. – Selfannihilation

Plus 1 for the cat :) – Avaricious

@Selfannihilation is there a way to use both of them QStandardItemModel and QSqltableModel? – Bursar

BTW @Selfannihilation I need a good source to learn Qt. can you suggest a good one? – Bursar

For books: If you want to learn the working mechanism of Qt, try An Introduction to Design Patterns in C++ with Qt 4; to learn how to use Qt, try C++ GUI Programming with Qt 4. For non-book resources: The best of the best is the Qt official document it self; Qt centre forum is also a good place to ask questions. Besides, you can check this asked question, some good on-line learning resources can be found there. – Selfannihilation

really i don't understand your answer, and it's my fault. I should do study some Qt. – Bursar

Answer 2

I got a question to read image from tableview, so I find the solution as fallow:

QImage name_image = table_store_multi_model_->item(i_row,0)->data(Qt::DecorationRole).value<QPixmap>().toImage();

Generally, we read data with data(), but here need a parameter "Qt::DecorationRole";

Cambrel