cropping image on QLabel using mouseEvent

[Dimple]

Hi ,,,i need to crop image displayed on label after dragging ,image is disappearing from the QLabel,, can anybody pls help me to fix this issue ??
i added this code

void MainWindow::mousePressEvent(QMouseEvent *ev)
{
if(ui->label->underMouse())
{
   //qDebug()<<"Entered Press";
    origin = ev->pos();

    if (!rubberBand)
        rubberBand = new QRubberBand(QRubberBand::Rectangle, this);

        rubberBand->show();

}
}

void MainWindow::mouseMoveEvent(QMouseEvent *ev)
{

rubberBand->setGeometry(QRect(origin, ev->pos()).normalized());
}

void MainWindow::mouseReleaseEvent(QMouseEvent *ev)
{
QPoint a = mapToGlobal(origin);
QPoint b = ev->globalPos();

a = ui->label->mapFromGlobal(a);
b = ui->label->mapFromGlobal(b);
rubberBand->hide();
QPixmap OriginalPix(*ui->label->pixmap());
double sx = ui->label->rect().width();
double sy = ui->label->rect().height();
sx = OriginalPix.width() / sx;
sy = OriginalPix.height() / sy;

a.setX(int(a.x() * sx));
b.setX(int(b.x() * sx));
a.setX(int(a.x() * sy));
b.setX(int(b.x() * sy));


QRect myRect(a,b);

QImage newImage;
newImage = OriginalPix.toImage();

QImage copyImage;
copyImage = copyImage.copy(myRect);

ui->label->setPixmap(QPixmap::fromImage(copyImage));
ui->label->repaint();

}

[VRonin]

QLabel is the wrong instrument for the job. have a look at this example: https://evileg.com/en/post/272/

[mrjj]

Hi
I think you used the wrong image by accident

you say

QImage newImage;
newImage = OriginalPix.toImage();
QImage copyImage;
copyImage = copyImage.copy(myRect); << copy empty

i think you meant.

QImage newImage;
newImage = OriginalPix.toImage();
QImage copyImage;
copyImage = newImage.copy(myRect); << copy from newImage

[Dimple]

@mjjj as u said i hv changed
copyImage=newImage.copy(myRect);

but here wat happens after dragged image,, its showing QLabel is completely black

[mrjj]

@Dimple
you mean when you drag the image to be cropped to the label ?

[Dimple]

yeah ,,after dragged the image ,,its showing QLabel is completely black (not shows image after cropped the image)

[Dimple]

[mrjj]

@Dimple
I think the mapping of the coordinates are a bit off so the rect copied is outside
the coordinates for label holding image.

[Dimple]

can u please send me correct code ,,,im not getting

[mrjj]

@Dimple
the calculations for the actual rect to copy

a = ui->label->mapFromGlobal(a);
b = ui->label->mapFromGlobal(b);

double sx = ui->label->rect().width();
double sy = ui->label->rect().height();

sx = OriginalPix.width() / sx;
sy = OriginalPix.height() / sy;

a.setX(int(a.x() * sx));
b.setX(int(b.x() * sx));
a.setX(int(a.x() * sy));
b.setX(int(b.x() * sy));

QRect myRect(a, b); // im not sure this rect is as intended.

try use qDebug to write it out and inspect the values.
like
qDebug() << " crop rect" << myRect;

[fouad2130]

This post is deleted!

[Dimple]

@mrjj

a.setX(int(a.x() * sx));
b.setX(int(b.x() * sx));
a.setY(int(a.y() * sy));
b.setY(int(b.y() * sy));

QRect myRect(a,b);

QImage newImage;
newImage = OriginalPix.toImage();
QImage copyImage;
copyImage=newImage.copy(myRect);
ui->label->setPixmap(QPixmap::fromImage(copyImage));
ui->label->setScaledContents(true);
ui->label->repaint();

now its working ,,i can crop the image but after cropped the image ,,,if i click on cropped image ,,image is disappearing?

[mrjj]

@Dimple
Hi
clicking the label triggers mousePressEvent and mouseReleaseEvent
so you will grab a very small /invalid area. ( thats my guess )

[Dimple]

@mrjj said in cropping image on QLabel using mouseEvent:

triggers

ok i ll change some functionality ,,Thanks for ur help

[mrjj]

@Dimple
Hi
i imagine a bool flag to tell it its in crop mode , else it will just ignore the mosuePress code etc.

[Dimple]

@mrjj

ok i ll check it out,,,thanks