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