rotate an image

[saman_artorious]

I have two images, one inside another. first I used two QFrame s and set background image via stylesheets.
but this was not a good idea as QFrame has no pixmap() member.
I changed QFrame to QLabel n set the background image of the inner image via stylesheets. (only the inner image shall rotate).

Now, I used the following code to try rotating QLabel background image, though I get segmentation fault, when assignig QLabel pixmap to the Qpixmap variable.

QPixmap pixmap(*ui->label_11->pixmap());
        QMatrix rm;
        rm.rotate(90);
        pixmap = pixmap.transformed(rm);
        ui->label_11->setPixmap(pixmap);

QPixmap pixmap(*ui->label_11->pixmap());
        QMatrix rm;
        rm.rotate(90);
        pixmap = pixmap.transformed(rm);
        ui->label_11->setPixmap(pixmap);

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[wysota]

• QWidget::paintEvent()
• QPainter::rotate()
• QPainter::drawPixmap()
• QPropertyAnimation

[Esther]

Im not a professional programmer, but there is something wrong with your code, check this image ratating sample code and have a comparison to check,hope this can help you.

[saman_artorious]

as I said I have one QLabel inside a QFrame. the label background image is a small movable part of the general frame background image. what I want is to rotate the smaller image according to a particular angle.

void MainWindow::rotate()
{
    QRectF target(0.0, 0.0, ui->label->width(), ui->label->height());
    QRectF source(0.0, 0.0, ui->label->width(), ui->label->height());
    QPixmap pixmap("path-to-image");
 
    QPainter painter(this);
    painter.rotate(90.0);
 
    painter.drawPixmap(target, pixmap, source);
 
}

void MainWindow::rotate()
{
    QRectF target(0.0, 0.0, ui->label->width(), ui->label->height());
    QRectF source(0.0, 0.0, ui->label->width(), ui->label->height());
    QPixmap pixmap("path-to-image");

    QPainter painter(this);
    painter.rotate(90.0);

    painter.drawPixmap(target, pixmap, source);

}

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I do not know how to link the pixmap to the label background after rotation!

[d_stranz]

What's wrong with QLabel::setPixmap()? Seems like the obvious thing to use after reading the QLabel documentation.

[saman_artorious]

Although I could rotate the inner image with the code below, the sad point is that, the background image always fit inside the inner QLabel. But, what I need is to rotate both the QLabel and the image simultaneously. or it will be better not to use QLabel at all this way. can I only load an extra image inside the outer frame background image and try to rotate it? I need help please.

QPixmap *orig_pixmap = new QPixmap();
    orig_pixmap->load("path-to-png");
    degrees++;
    if(degrees == 90) degrees = 0;
    QTransform rotate_disc;
    rotate_disc.translate((orig_pixmap->width()-ui->label->width())/2 , (orig_pixmap->width()-ui->label->height())/2);
    rotate_disc.rotate(degrees,Qt::ZAxis);
    QPixmap pixmap;
    //pixmap = orig_disc->scaled(89,89,Qt::IgnoreAspectRatio,Qt::SmoothTransformation);
    pixmap = orig_pixmap->transformed(rotate_disc,Qt::SmoothTransformation);
    ui->label->setPixmap(pixmap);

QPixmap *orig_pixmap = new QPixmap();
    orig_pixmap->load("path-to-png");
    degrees++;
    if(degrees == 90) degrees = 0;
    QTransform rotate_disc;
    rotate_disc.translate((orig_pixmap->width()-ui->label->width())/2 , (orig_pixmap->width()-ui->label->height())/2);
    rotate_disc.rotate(degrees,Qt::ZAxis);
    QPixmap pixmap;
    //pixmap = orig_disc->scaled(89,89,Qt::IgnoreAspectRatio,Qt::SmoothTransformation);
    pixmap = orig_pixmap->transformed(rotate_disc,Qt::SmoothTransformation);
    ui->label->setPixmap(pixmap);

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[wysota]

#include <QtGui>
 
class Widget : public QWidget {
  Q_OBJECT
  Q_PROPERTY(int rot1 READ rot1 WRITE setRot1);
  Q_PROPERTY(int rot2 READ rot2 WRITE setRot2);
public:
  Widget(QWidget *parent = 0) : QWidget(parent) { m_rot1 = 0; m_rot2 = 0; }
  void setPixmap1(QPixmap px) { m_px1 = px; update(); }
  void setPixmap2(QPixmap px) { m_px2 = px; update(); }
  int rot1() const { return m_rot1; }
  int rot2() const { return m_rot2; }
public slots:
  void setRot1(int r1) { m_rot1 = r1; update(); }
  void setRot2(int r2) { m_rot2 = r2; update(); }
protected:
  void paintEvent(QPaintEvent *) {
    QPainter p(this);
    p.setRenderHint(QPainter::Antialiasing);
    p.translate(width()/2, height()/2);
    if(!m_px1.isNull()) {
      p.save();
      p.rotate(m_rot1);
      QRect r = m_px1.rect();
      r.moveCenter(QPoint(0,0));
      p.drawPixmap(r, m_px1);
      p.restore();
    }
    if(!m_px2.isNull()) {
      p.save();
      p.rotate(m_rot2);
      QRect r = m_px2.rect();
      r.moveCenter(QPoint(0,0));
      p.drawPixmap(r, m_px2);
      p.restore();
    }
  }
private:
  int m_rot1;
  int m_rot2;
  QPixmap m_px1, m_px2;
};
 
#include "main.moc"
 
int main(int argc, char **argv) {
  QApplication app(argc, argv);
  Widget w;
  w.setPixmap1(QPixmap("/usr/share/icons/default.kde4/64x64/actions/system-lock-screen.png"));
  w.setPixmap2(QPixmap("/usr/share/icons/default.kde4/64x64/actions/application-exit.png"));
  w.resize(100,100);
  QPropertyAnimation anim1(&w, "rot1");
  QPropertyAnimation anim2(&w, "rot2");
  anim1.setStartValue(0);
  anim2.setStartValue(0);
  anim1.setEndValue(359);
  anim2.setEndValue(-359);
  anim1.setLoopCount(-1);
  anim2.setLoopCount(-1);
  anim1.setDuration(5000);
  anim2.setDuration(3000);
  anim1.start();
  anim2.start();
  w.show();
  return app.exec();
}

#include <QtGui>

class Widget : public QWidget {
  Q_OBJECT
  Q_PROPERTY(int rot1 READ rot1 WRITE setRot1);
  Q_PROPERTY(int rot2 READ rot2 WRITE setRot2);
public:
  Widget(QWidget *parent = 0) : QWidget(parent) { m_rot1 = 0; m_rot2 = 0; }
  void setPixmap1(QPixmap px) { m_px1 = px; update(); }
  void setPixmap2(QPixmap px) { m_px2 = px; update(); }
  int rot1() const { return m_rot1; }
  int rot2() const { return m_rot2; }
public slots:
  void setRot1(int r1) { m_rot1 = r1; update(); }
  void setRot2(int r2) { m_rot2 = r2; update(); }
protected:
  void paintEvent(QPaintEvent *) {
    QPainter p(this);
    p.setRenderHint(QPainter::Antialiasing);
    p.translate(width()/2, height()/2);
    if(!m_px1.isNull()) {
      p.save();
      p.rotate(m_rot1);
      QRect r = m_px1.rect();
      r.moveCenter(QPoint(0,0));
      p.drawPixmap(r, m_px1);
      p.restore();
    }
    if(!m_px2.isNull()) {
      p.save();
      p.rotate(m_rot2);
      QRect r = m_px2.rect();
      r.moveCenter(QPoint(0,0));
      p.drawPixmap(r, m_px2);
      p.restore();
    }
  }
private:
  int m_rot1;
  int m_rot2;
  QPixmap m_px1, m_px2;
};

#include "main.moc"

int main(int argc, char **argv) {
  QApplication app(argc, argv);
  Widget w;
  w.setPixmap1(QPixmap("/usr/share/icons/default.kde4/64x64/actions/system-lock-screen.png"));
  w.setPixmap2(QPixmap("/usr/share/icons/default.kde4/64x64/actions/application-exit.png"));
  w.resize(100,100);
  QPropertyAnimation anim1(&w, "rot1");
  QPropertyAnimation anim2(&w, "rot2");
  anim1.setStartValue(0);
  anim2.setStartValue(0);
  anim1.setEndValue(359);
  anim2.setEndValue(-359);
  anim1.setLoopCount(-1);
  anim2.setLoopCount(-1);
  anim1.setDuration(5000);
  anim2.setDuration(3000);
  anim1.start();
  anim2.start();
  w.show();
  return app.exec();
}

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[saman_artorious]

There is something I need to know. As in my case I have a MainWindow of so many tools n widgets. would it be all right if I inherit from QWidget publicly in MainWindow class?
that way I can load as much anim n pixmaps as I need in the project main window. The main window paintEvent would be customized then. is that ok?

[saman_artorious]

Wysota
The the rotation axis of the second image is its center. However, I may want to set one side of the rectangle fixed and or even rotate it from a certain point. Is that possible?

[wysota]

Yes, of course. You can manipulate the painter in any way you want using rotate(), scale() and translate().