Visualize an Image and copy a portion

[Polielia]

Hi, my goal is to visualize an image (e.g. in a QLabel), allow the use to select a portion of this image and visualize this portion in another QLabel. I have written the code, but I have a problem, the portion of image that I visualize is different from the selected part
CODE CPP

void Button1_nyq::on_selectimage_nyq_Hom_clicked() 
{

        Imagename = QFileDialog::getOpenFileName(this,tr("Open Image for Nyquist Test"), "", tr("Images (*.jpg)"));  //open image
        //visualize the image
        QPixmap image(Imagename);
        ui->ImageDisplay->setPixmap(image);  //ImageDisplay is the name of the QLabel
    }
int count_selection=0; //when it is not 0 it mean that the user want to make another selection and I hide the previous 

void Button1_nyq::mousePressEvent(QMouseEvent *e)
{
        if(count_selection!=0)
                rubberBand->hide();
        point1 = e->pos();
        rubberBand = new QRubberBand(QRubberBand::Rectangle,this );
}

void Button1_nyq::mouseMoveEvent(QMouseEvent *e)
{
        rubberBand->show();
        rubberBand->setGeometry(QRect(point1,e->pos()));
}

void Button1_nyq::mouseReleaseEvent(QMouseEvent *e)
{
        count_selection++;
        QRect rect; //selection rectangle
        rect.setTopLeft(point1);
        rect.setBottomRight(e->pos());
        QPixmap image(Imagename);
        QPixmap a = image.copy(rect); //copy the image selected in a
        ui->label_image_selected->setPixmap(a); //visualize the image in the second QLabel 
    }
}

.h

#ifndef BUTTON1_NYQ_H
#define BUTTON1_NYQ_H

#include <QDialog>
#include <qrubberband.h>

namespace Ui {
class Button1_nyq;
}

class Button1_nyq : public QDialog
{
    Q_OBJECT

public:
    explicit Button1_nyq(QWidget *parent = 0);
    ~Button1_nyq();

private slots:
    void on_selectimage_nyq_Hom_clicked();

    void on_SAVE_clicked();

    void mousePressEvent(QMouseEvent *e);

    void mouseReleaseEvent(QMouseEvent *e);

    void mouseMoveEvent(QMouseEvent *e);

private:
    Ui::Button1_nyq *ui;
    QRubberBand *rubberBand;
};

#endif // BUTTON1_NYQ_H

what i'm doing wrong ? :)

[VRonin]

Problem is that e->pos() is relative to Button1_nyq not to the label displaying the image

use e->globalPos() and QLabel::mapFromGloabal to convert it back to coordinates relative to the image

[Polielia]

thanks to VRonin now it seems better, but I still have a problem. when I visualize the selected part of image, the second label show the image of a identical rect but in a different position, near the real position. How can I fix it?

void Button1_nyq::on_selectimage_nyq_Hom_clicked() 
{

        Imagename = QFileDialog::getOpenFileName(this,tr("Open Image for Nyquist Test"), "", tr("Images (*.jpg)"));  //apro l'immagine
        //visualize the image in the first Label
        QPixmap image(Imagename);
        ui->ImageDisplay->setPixmap(image);  //ImageDisplay is the name of QLabel
    }
int count_selection=0; ///when it is not 0 it mean that the user want to make another selection and I hide the previous 


void Button1_nyq::mousePressEvent(QMouseEvent *e)
{
        if(count_selection!=0)
                rubberBand->hide();
        point1 = e->pos();
        rubberBand = new QRubberBand(QRubberBand::Rectangle,this );
}

void Button1_nyq::mouseMoveEvent(QMouseEvent *e)
{
        rubberBand->show();
        rubberBand->setGeometry(QRect(point1,e->pos()));
}

void Button1_nyq::mouseReleaseEvent(QMouseEvent *e)
{
        count_selection++;
        QRect rect; //selection rectangle
        rect.setTopLeft(point1);
        rect.setBottomRight(e->pos()));
       QPixmap image(rect.size());
        ui->ImageDisplay->render(&image,QPoint(0,0),QRegion(rect)); //copy the selected part into "image"
        ui->label_image_selected->setPixmap(image); //show "image" in the second QLabel

this is the result
Real image
http://imgur.com/9f6e0D3
Selected image
http://imgur.com/lysvM0q
Result
http://imgur.com/s0FydTc

[Polielia]

I solved my problem, this is my solution:

void Button1_nyq::on_selectimage_nyq_Hom_clicked() 
{
 
        Imagename = QFileDialog::getOpenFileName(this,tr("Open Image for Nyquist Test"), "", tr("Images (*.jpg)"));  //apro l'immagine
        //visualize the image in the first Label
        QPixmap image(Imagename);
        ui->ImageDisplay->setPixmap(image);  //ImageDisplay is the name of QLabel
    }
 
void Button1_nyq::mousePressEvent(QMouseEvent *e)
{
 
        point1 = e->pos();
        rubberBand = new QRubberBand(QRubberBand::Rectangle,this );
}
 
void Button1_nyq::mouseMoveEvent(QMouseEvent *e)
{
        rubberBand->show();
        rubberBand->setGeometry(QRect(point1,e->pos()));
}
 
void Button1_nyq::mouseReleaseEvent(QMouseEvent *e)
{
        rubberband->hide();
        QRect rect; //selection rectangle
        rect.setTopLeft(point1);
        rect.setBottomRight(e->pos()));
 
       QPixmap image(rect.size());
       image = grab(rubberband->geometry()); //copy the selected part
        ui->label_image_selected->setPixmap(image); //show "image" in the second QLabel