How to get position or mouse click event in QLabel

jsulm

@ManiRon28 said in How to get position or mouse click event in QLabel:

Actually I made some changes to the code

And does it work now? If not: what is the issue now? Please provide needed information when asking.

JonB

@ManiRon28
If you get the qDebug("DATA"); output then you know the emit clicked(this); will be executed.

What makes you think it is not? There is nothing in your code as shown to tell you this.

Show your connect() statement. Show that is executed. And do yourself a favour and stop using SIGNAL/SLOT() old-style connection syntax, there is a reason it was replaced a decade ago....

P.S.
Please use the forum's Code tags around your code, it makes it easier for others.

ManiRon28

@JonB , @jsulm
Hi
My connect call

connect(ui->label,SIGNAL(clickedlabel(QPoint &)),this, SLOT(points(QPoint &)));

Clicklabel.h

#ifndef CLICKLABEL_H
#define CLICKLABEL_H

#include <QLabel>
#include <QObject>
#include <QWidget>
#include<QMouseEvent>
#include<QPoint>

class Clicklabel : public QLabel
{
    Q_OBJECT
public:
    Clicklabel(QWidget* parent = 0);
    ~Clicklabel();

protected:
    void mousePressEvent(QMouseEvent *mouseEvent);
signals:
    void clickedlabel(QPoint &);
};

#endif // CLICKLABEL_H

Clicklabel.cpp

void Clicklabel::mousePressEvent(QMouseEvent *mouseEvent)
{
    QPoint  mouse_pos = mouseEvent->pos();

    if(mouse_pos.x() <= this->size().width() && mouse_pos.y()<= this->size().height())
    {
        if(mouse_pos.x() >0 && mouse_pos.y()>0)
        {
            emit clickedlabel(mouse_pos);
        }
    }
}

Mainwindow.cpp

void MainWindow::points(QPoint &pos)
{
    qDebug("DataVal",pos.x(),pos.y());
}

Now I am able to view the debug print "DataVal" but I am not able to get the values of X and Y

JonB

@ManiRon28 said in How to get position or mouse click event in QLabel:

but I am not able to get the values of X and Y

What does this actually mean? Your qDebug() does print out pos.x(),pos.y(), so you do "get values"....

ManiRon28

@JonB no I dont get any values from the X and Y , only the DataVal string gets printed

This is how mu print is coming

jsulm

@ManiRon28 Please use qDebug properly:

void MainWindow::points(QPoint &pos)
{
    qDebug() << "DataVal" << pos.x() << pos.y();
}

JonB

@ManiRon28
That is because your call to qDebug() is incorrect.

qDebug() << "DataVal" << pos.x() << pos.y());

ManiRon28

@JonB, @jsulm oh sorry thanks for correcting me,

I have one more doubt

Is there any way to differentiate between left and right mouse click

jsulm

@ManiRon28 It's all in the documentation:

ManiRon28

@jsulm, @JonB Thanks for providing me the necessary details

I have a qlabel and now I am able to detect the click/press event in label, but I want to capture the coordinates based on image size

For example
The image size is 100x100 and the qlabel size is 200x200, I should get coordinates when I press on the image and not on the other part of qlabel which doesnt have image or empty

JonB

@ManiRon28
I assume by "image" you mean QLabel::pixmap()? So you need to find where that is within the label. I don't know, but if you start with qDebug() << this->pixmap()->rect() what does that tell you, can you get from that where the pixmap is positioned within the label?

ManiRon28

@JonB Yes the image is loaded using pixmap

JonB

@ManiRon28 Good.

ManiRon28

@JonB

I get the ouput like this

x = pos.x();
y=pos.y();

    int XVal = ui->labelImage->pixmap().rect().x();
    int YVal = ui->labelImage->pixmap().rect().y();
    int widthVal = ui->labelImage->pixmap().rect().width();
    int heightVal = ui->labelImage->pixmap().rect().height();


    QString qsVal = "x = " + QString::number(XVal) + ", y = " + QString::number(YVal) + ", Width = " + QString::number(widthVal) + ", height = " + QString::number(heightVal);

x = 522, y =78, Button = LEFT, 
Rect - x = 0, y = 0, Width = 1379, height = 516

jsulm

@ManiRon28 If you know where the pixmap is located inside the QLabel and you get the mouse coordinates inside the QLabel then it is simple math to get the coordinates inside the pixmap, right?

ManiRon28

@jsulm
Can you please specify the procedure which would be helpful

jsulm

@ManiRon28 Come on, this is really basic.
Let's say xPixmap is the x coordinate of the pixmap inside the QLabel and xMouse is the x coordinate where the use clicked inside the QLabel. Then the x coordinate inside the pixmap is: xMouse - xPixmap.

ManiRon28

@jsulm

Hi When I try to get the X and Y coordinate of pixmap I get the values as Zero

ui->label->pixmap().rect().x();
ui->label->pixmap().rect().y();

and I found out that the width and height of QLabel is 950400 and the pixmap width is 948398

kindly help me with it

jsulm

@ManiRon28 said in How to get position or mouse click event in QLabel:

When I try to get the X and Y coordinate of pixmap I get the values as Zero

This simply means that the pixmap is located at 0,0 inside the label, so what is the problem?

Pl45m4

@ManiRon28 said in How to get position or mouse click event in QLabel:

and I found out that the width and height of QLabel is 950400 and the pixmap width is 948398

I think you mean 900x400 (948x398)?!
The 2px difference could be a frame of QLabel.

I should get coordinates when I press on the image and not on the other part of qlabel which doesnt have image or empty

Simply math / geometry.

You have the image rectangle and you have your mouseClick coordinates.

https://www.geeksforgeeks.org/check-if-a-point-lies-on-or-inside-a-rectangle-set-2/

Edit:
You dont even have to calculate it yourself. There is QRect::contains(QPoint)

https://doc.qt.io/qt-6/qrect.html#contains

So pass your point you get from clickedLabel(QPoint) to that check function and do whatever you want to do, if it's inside the image rect (function will return true then).
And how to get the equivalent point on your pixmap, if you want to do something with your image data, @jsulm has explained here:

@jsulm said in How to get position or mouse click event in QLabel:

Let's say xPixmap is the x coordinate of the pixmap inside the QLabel and xMouse is the x coordinate where the use clicked inside the QLabel. Then the x coordinate inside the pixmap is: xMouse - xPixmap.

same for y of course