scene = new QGraphicsScene();
view = new QGraphicsView(this);
scene->addPixmap(QPixmap( "xyz.jpeg" ));
scene->setSceneRect(0,0,325,302);
//scene->setSceneRect(scene->itemsBoundingRect());
view->setScene( scene );
view->show();
I have this code in Mainwindow constructor. Image is loading but. I must scroll to see all image (I can only vertical scroll??? why???) I want see image in orginal size. Image must loading when app start.
You set the size of the scene, but not the view. The view is like a window into the scene, so if it's smaller, then you'll need to scroll to see the other parts of the scene. If the view and the scene match in size, no scrolling will be required.
Therefore, set the scene and view to a size larger than the pixmap to ensure you won't need to scroll to see the pixmap and the view to the same size as the scene to remove scrolling completely.
ui->graphicsView->fitInView();
if you put your scene or image or whatever in the brackets it should be fit to view size :)
Related
I have a QTabWidget and second page containing a QGraphicsView with scene. The scene canvas is larger than the QGraphicsView's viewport and I'm using QScrollBar to move objects on the scene.
On the scene I place a lot of QGraphicsItem objects. I have a horizontal and a vertical scroll bar, and some items can move only horizontally, another objects on scene can move only vertically.
My QGraphicsview coordinates start at the top left corner of QGraphicsview. After moving objects on the scene, if I change the page of the QTabWidget from second page to first and then back again, the start of coordinates is moved to the center of QGraphicsView, and all objects on the scene are moved to new positions automatically.
This happens only when I'm using a QTabWidget, if I change the parent of QGraphicsView to QWidget, all works well.
I found a solution. Just need to calculate rect of the scene, and set obviously using QGraphicsScene::setSceneRect() method. Otherwise, position of my scene in the QGraphicsView may surprise.
I am trying a play a video(640 * 360) through rtsp in QGraphicsView. But the issue is that it is not fitting completely within the view and scroll bar is appearing, which should not happen. And moreover, I am able to get the same peace of code working properly in Linux environment but I am getting the issue in windows.
Please find the code snippet below, If anyone can point out the error I am making will be helpful.
scene = new QGraphicsScene(this);
view= new graphicsView();
view->setScene(scene);
videoItem = new QGraphicsVideoItem;
player= new QMediaPlayer;
player->setVideoOutput(videoItem);
view->scene()->addItem(videoItem);
controlLayout = new QHBoxLayout;
controlLayout->setMargin(0);
controlLayout->addWidget(view);
view->setSceneRect(scene->sceneRect());
view->scale(1.97,1.97);
ui.m_pframePlay->setLayout(controlLayout);
ui.m_pframePlay->show();
player->setMedia(QUrl("rtsp:..."));
player->play();
The documentation for QGraphicsView sais about setSceneRect
The scene rectangle defines the extent of the scene, and in the view's case, this means the area of the scene that you can navigate using the scroll bars.
This means, setSceneRect does not resize the visible area of the view but only which area of the scene is visible in the view. So I guess you simply have to resize your view, e.g.
view->resize(scene->width()*1.97, scene->height()*1.97)
(I scaled width/height with 1.97 because you scale your view using factor 1.97 for some reason).
in Qt 4.8 i have create a QGraphicsView and a DynamicRadarScene(derived from QGraphicsScene):
QGraphicsView* view = new QGraphicsView;
view->setMinimumSize(800, 600);
DynamicRadarScene* _scene = new DynamicRadarScene(mode, channel_types, this);
view->setScene(_scene);
What is the coordinate system of QGraphicsScene? (0,0) is from upper left corner?
How can i draw an item in the upper right corner of the scene (i have set it 800x600: view->setMinimumSize(800, 600);)?
If i resize the widget and so i resize the QGraphicsView, how can move the item i have drawn before to remain in the upper left corner?
Yes, the upper left corner is generally the coordinate of (0,0) in a graphics scene. What you need to consider is that a QGraphicsView is like a window looking into a world (the QGraphicsScene). You set the view to look at an area or the scene, which may be all or just part of the scene.
Once the scene and view are setup, you can then add QGraphicsItems / QGraphicsObjects or instances of classes derived from those by using functions such as QGraphicsScene::addItem. These items are positioned in the scene and draw themselves.
i (sic) resize the widget and so i resize the QGraphicsView
You can change the QGraphicsView position and dimensions, but then the items in the scene will remain in the same place within the scene. Usually you would set up the scene and view and then move / resize the graphics items / objects within the scene, often with the setPos function: QGraphicsItem::setPos(). This sets the position of the item, relative to its parent. If the item has no parent, it sets the position of the item in the scene.
QGraphicsScene has property sceneRect. If it is not set then it is auto adjusted depending on scene content. This can give a filling that origin of coordinating is in some strange place or even that it is mobile.
Set this property. See also this.
Whenever I add a new item to a QGraphicsScene, the origin of the QGraphicsScene seem to change for the position of the item I have just added.
How to make the QGraphicsScene origin fixed?
Do I need to add the item first in the QGraphicsScene and then specify a position for the item?
Well, by default the content of the scene will be centered in the QGraphicsView. The origin of the graphics scene does not change randomly.
You might want to use setSceneRect() to define the size of the scene, so that the QGraphicsView always centers the scene in the view in a fixed manner. (If you don't set it manually, the rect will be calculated based on the items in the scene, which changes if you add more.)
I answered a related question about a year ago that may be helpful:
How to draw a point (on mouseclick) on a QGraphicsScene?
Ditto to what badcat.
There are a lot of controls for adjusting or manipulating your viewport(s) that you have pointing at your scene. The scene sets what is on the stage. The view is how you look at it. Be sure to set the sceneRect or set it indirectly using centerOn or fitInView or scale or translate from the QGraphicsView class.
http://qt-project.org/doc/qt-4.8/graphicsview.html
http://qt-project.org/doc/qt-4.8/qgraphicsview.html
QGraphicsScene::setSceneRect ( const QRectF & rect ) will make it absolute.
see http://doc.qt.digia.com/qt/qgraphicsscene.html#sceneRect-prop
I know that this is a very specific C++ and Qt related question, but maybe someone can help me, anyway ...
See the code below: I want to display an image within a scroll area. The view port of the scroll area shall have a defined initial size. That means, if the image's size is bigger than the initial size of the view port, scroll bars will be visible, otherwise not.
// create label for displaying an image
QImage image( ":/test.png" );
QLabel *label = new QLabel( this );
label->setPixmap( image.toPixmap() );
// put label into scroll area
QScollArea *area = new QScrollArea( this );
area->setWidget( label );
// set the initial size of the view port
// NOTE: This is what I'd like to do, but this method does not exist :(
area->setViewPortSize( QSize( 300, 300 ) );
It shall be possible to resize the whole application so that the view port will get another size than the initial one.
Unfortunatelly I was not able to find out, how to set the size of the view port. Qt's layout mechanism seems to set a default size for the view port, but up to now I was not able to change it. Setting a new size with
area->setMinimumSize( QSize( 300, 300 ) );
will actually set the demanded size, but then the scroll area looses the ability to get resized to a size smaller than 300x300.
Any ideas?
I think that you are looking at the problem the wrong way. The QScrollArea is just a widget that you put in a frame or QMainWindow. The size of the widget is controlled by the layout of the widget that contains it.
Take a look at this example from Trolltech: Image Viewer Example
You can try:
class MyScrollArea : public QScrollArea
{
virtual QSize sizeHint() const { return QSize( 300, 300 ); }
};
// create label for displaying an image
QImage image( ":/test.png" );
Label *label = new QLabel;
label->setPixmap( image.toPixmap() );
// put label into scroll area
QScollArea *area = new MyScrollArea( this );
area->setWidget( label );
However layout and Qt is amazingly Voodoo. It is IMO its least functional part.
if that doesn't work, try calling QWidget::resize() on various widgets.
Is the scroll area the top level widget? If so, simply call
area->resize(300,300);
If it's inside a hierarchy you need to resize the toplevel appropriately (complex), or set the minimumSize of the area. You could also try to experiment with the LayoutPolicy - assuming the sizeHint is QSize(300,300) you can give it the appropriate size policy according to what's defined in https://doc.qt.io/qt-5/qsizepolicy.html#Policy-enum
I don't think you can do exactly that very easily, which is (if I'm reading correctly), size the widget so that the internal area is 300x300. You might be able to fudge it, however, since a scroll area is a type of frame, which inherits from QWidget. This means you could just call area->resize( 300 + fudge, 300 + fudge ), where your fudge values account for the extra bit taken up by the frame's drawing.
I'm not sure this would work in a dynamically resizable dialog, however. I haven't ever done anything quite like this.
If you're trying to display an image inside a scroll area, your best bet isn't going with a label.
You should try using a QGraphicsView/QGraphicsScene/QGraphicPixmapItem (instead of the Scroll Area and label). The performance is far better when displaying images. The scroll area and label will re-draw the image very poorly as you move around using the scroll bars.
For example, you have a ".ui" file with a QGraphicsView on the gui called "qgvImageView" and a QImage called "image"...
QGraphicsScene *scene = new QGraphicsScene(qgvImageView);
QPixmap pixTmp(QPixmap::fromImage(image));
QGraphicsPixmapItem * ppixItem = scene->addPixmap( pixTmp );
ppixItem->setPos(0,0);
Check out the QT Documentation. BTW: This was introduced in Qt 4.2
I'm not sure if this will specifically fix the problem, but there is a chance that the QGraphicsView will react better to what you're trying to do.
How about using
area->setGeometry(int x, int y, int w, int h);