Passing QPixmap Object Between Main and Sub Forms

[R_Irudezu]

I saw some samples but connect() mechanism looked weird a bit to me. I'm trying to understand it.

Currently I have a QLabel in MainWindow, and it has a QPixmap (covered with image).

Let's say there is a button and it has button_clicked() event. When button clicked, it should pass MainWindow's QLabel to sub form. So i need to pass this QLabel(as image) to another form and show it in another form's QLabel (as image).

I think it's a good way to use connect(), SLOT & SIGNAL mechanism, like i said i'm trying to understand it. Or maybe there's a better way to do pass QLabel to another form. I'm waiting for your helpful and explanatory answers.

[SGaist]

Hi,

Something is not clear, do you want to move the QLabel around or the image it contains ? If the later, where does that image come from ?

[R_Irudezu]

@SGaist second one, the image comes from a database (blob data).

At Main Form:

//strQuery contains how i get blob data from a local Database
QByteArray outByteArray = strQuery.value(0).toByteArray();
QPixmap outPixmap = QPixmap();
outPixmap.loadFromData( outByteArray );
QPixmap pixmap = outPixmap;

QImage image;
image = image.scaledToWidth(ui->QLabel1->width(), Qt::SmoothTransformation);
ui->QLabel1->QLabel::setPixmap(pixmap);
//until here, i loaded blob data to a QLabel

The QLabel shows blob data, it's OK. Now i want to show same blob data in other form. Yes i can do with the same way, get from db again but that's not way i want.

I just need to show QLabel's image in sub form. Did i explain well?

[mrjj]

@R_Irudezu
Hi
So the sub form should also have a label to hold image (pixmap) as
moving mainwindows actual label will be odd.
Lets call it subforms label for sublabel.
so you add a function to subform for setting it
( as the UI is private from outside)
like
void SubFormName::setImage(QPixmap pix) {
ui->subLabel->setPixmap(pix);
}

and then when in Main form, where/when u show sub form
SubForm * mysub=new SubForm(this);
// we call our function to transfer image to sub form
mysub->setImage( ui->QLabel1->pixmap() );
mysub->show();

note you need to delete subform again at some point!
using a QDialog as subForm would make this easier if
its ok, that mainwindow is blocked while sub form is open.

[R_Irudezu]

@mrjj when i do

mysub->setImage( ui->QLabel1->pixmap() );

ui keyword is underlined and this error:

no viable conversion from const QPixmap * to QPixmap

I solved it with create a new const QPixmap *;

const QPixmap *pixMap = ui->QLabel1->pixmap();
//then
mysub->setImage( ui->QLabel1->pixmap() );

It's ok now. Many thanks @Lifetime-Qt-Champion

[mrjj]

@R_Irudezu
Ah sorry, my bad.
I thought it would return a copy.
but its
const QPixmap * pixmap() const
Should be fine as a copy is made so even if original image should
be removed, the subForm has its own.