QLabel snap to ScrollBar

mrjj

Hi
You could do as in
https://doc.qt.io/qt-5/qtwidgets-widgets-imageviewer-example.html
and use a ScrollArea with the label inside.
However, this is for normal scrolling when the image is bigger than area where its
displayed.
It sounds a bit like you have some other sort of zoom in mind ?

Mikeeeeee

Thanks.
I included ImageViewer in the project. But how to use ImageViewer?
I tried to create a QWidget and change the class to ImageViewer, but got an error.

mrjj

Hi
You can just new an instance put where you want it
ImageViewer * MyImg = new ImageViewer(this);

Mikeeeeee

@mrjj said in QLabel snap to ScrollBar:

ImageViewer * MyImg = new ImageViewer(this);

So I get the error: no matching constructor for initialization of 'ImageViewer'

mrjj

@Mikeeeeee
well its constructor is
ImageViewer();
so it doesn't take a parent. you change that so it can be imbedded into what you like.

Mikeeeeee

How to set picture? Need a method to move from private to public?

mrjj

@Mikeeeeee
hi
yes you can make setImage public

Mikeeeeee

I did so:

    QImage mapImage(":/Images/Images/mapMain.png");
    ImageViewer* myImageViewer  = new ImageViewer();
    myImageViewer->setImage(mapImage);

I have a label: ui->labelMap
How do I set to myImageViewer to ui->labelMap?

mrjj

@Mikeeeeee
You cannot put whole viewer into a Label.
However, you can use myImageViewer instead of
ui->labelMap

Mikeeeeee

But how to use? How to do this?

mrjj

@Mikeeeeee
well do you have ui->labelMap in layout ?
then just insert myImageViewer into that.

Mikeeeeee

How to do this? I created ui->label Map in the designer.

mrjj

@Mikeeeeee
but is it a layout?

Mikeeeeee

I appent ui->label in the ui->gridLayout_2

Mikeeeeee

Also I have an empty ui->verticalLayout

mrjj

@Mikeeeeee said in QLabel snap to ScrollBar:

ui->gridLayout_2

ok then do
ui->gridLayout_2->addWidget(myImageViewer);
You can delete the label if u wish.

Mikeeeeee

Cool, works. And how to reconfigure the mouse wheel to zoom in?

mrjj

@Mikeeeeee
Its not a configure option. Its new code :)
You can override (add) wheelEvent ( QWheelEvent * event ) to the
ImageViewer class and change the size of the inner QLabel *imageLabel;
to create a zoom in effect.
Or create your on drawing function like here
https://stackoverflow.com/questions/6650219/zooming-function-on-a-qwidget

Mikeeeeee

I tried to do so, but it does not work. Please tell me how to set up the signal?

connect(imageLabel, &QWidget:: wheelEvent(), this, &ImageViewer::zoomIn);

mrjj

@Mikeeeeee
Hi
Its not a signal but a virtual function.
You have to override it.

Right clik on the class name
alt text
Then select

and you get the function

protected:
    virtual void wheelEvent(QWheelEvent *event) override
    {
    }

Then do same right click again and select
alt text

to move the body of function to the cpp file.

Now you can try to implement your zoom.