I want to use QListWidget to display big images, e.g. 3508×4961 size in pixels, each list item will display one image. The image is set in a Qlabel and the Qlabel is set into the QListWidgetItem by setItemWidget(). When my program is running, the list item cannot display the entire image because the image is too large. It only displays the upper part of an image. When I scroll down, the list item changes to the next image immediately instead of showing the lower part of the current image gradually. Does anyone know how to show the lower part of each image by scrolling?
Here is my code,
QImage *image = new QImage("/home/sk/image1.png");
QLabel *label = new QLabel;
label->setPixmap(QPixmap(QPixmap::fromImage(*image)));
QListWidgetItem *ite = new QListWidgetItem;
auto size = label->sizeHint();
ite->setSizeHint(label->sizeHint());
size = ite->sizeHint();
ui->listWidget->addItem(ite);
ui->listWidget->setItemWidget(ite, label);
image = new QImage("/home/sk/image2.png");
label = new QLabel;
label->setPixmap(QPixmap(QPixmap::fromImage(*image)));
ite = new QListWidgetItem;
ite->setSizeHint(label->sizeHint());
ui->listWidget->addItem(ite);
ui->listWidget->setItemWidget(ite, label);
image = new QImage("/home/sk/image3.png");
label = new QLabel;
label->setPixmap(QPixmap(QPixmap::fromImage(*image)));
ite = new QListWidgetItem;
ite->setSizeHint(label->sizeHint());
ui->listWidget->addItem(ite);
ui->listWidget->setItemWidget(ite, label);
have you tried changing the scroll mode to ScrollPerPixel
setVerticalScrollMode
and
setHorizontalScrollMode
ui->listWidget->setVerticalScrollMode(QListWidget::ScrollPerPixel);
and in order to change the scroll step
ui->listWidget->verticalScrollBar()->setSingleStep(10);
ui->listWidget->verticalScrollBar()->setPageStep(20);
these values will be used for scrolling
I have a problem, i'm developing a graphical program under Windows, there are few QGraphicsScene and one QGraphicsView that it is possible to change the Scenes in runtime with a lot of graphics items, the problem is when I use Qwidget viewport everything works but when I switch to OpenGL viewport when I change the scene the content of previous scene still appear on the QGraphicsView and the contents of new Scene appear too.
what is the problem ? is it the changing Scenes method best solution or should I change the method ?
here is the code to setup View
m_viewPort = new QOpenGLWidget (this);
QSurfaceFormat format;
format.setProfile(QSurfaceFormat::CoreProfile);
format.setDepthBufferSize(24);
format.setStencilBufferSize(8);
format.setSamples(4);
m_viewPort->setFormat(format);
ui->gV->setViewport(m_viewPort);
ui->gV->setViewportUpdateMode(QGraphicsView::FullViewportUpdate);
//ui->gV->setCacheMode(QGraphicsView::CacheBackground);
ui->gV->setRenderHints(QPainter::Antialiasing| QPainter::HighQualityAntialiasing | QPainter::SmoothPixmapTransform| QPainter::TextAntialiasing);
ui->gV->setHorizontalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
ui->gV->setVerticalScrollBarPolicy (Qt::ScrollBarAlwaysOff);
ui->gV->setTransformationAnchor(QGraphicsView::NoAnchor);
ui->gV->setAutoFillBackground(false);
ui->gV->setAttribute(Qt::WA_OpaquePaintEvent, true);
ui->gV->setAttribute(Qt::WA_NoSystemBackground, true);
resize(boardBaseSize);
here is code to set the new scene to the view
void GlScreenBoard::setShowScene(QGraphicsScene *scene, QString programName)
{
scene->setSceneRect(boardSceneRectBase);
ui->gV->setScene(scene);
}
another problem is when I set Graphics view CacheMode to CacheBackground the OpenGL viewport disables !! and the painter in QGraphicsScene returns to Raster !
I want to overlay a QGLWidget with clickable buttons.
I'm using a QGraphicsView and setting the viewport to a QGLWidget. Then I'm adding a layout to the QGraphicsView, and adding several QPushButtons to that.
The Buttons display correctly, HOWEVER they are not clickable.
Here is my code:
QGraphicsView* view = ui->gView;
QGLWidget* gl = new QGLWidget(QGLFormat(QGL::SampleBuffers));
view->setViewport(gl);
QPushButton* push = new QPushButton("Click me");
QHBoxLayout* h = new QHBoxLayout;
QPushButton* wo = new QPushButton("Wo");
h->addWidget(wo);
h->addWidget(push);
view->setLayout(h);
Is there a simple way I can make the buttons get the clicks when the mouse is above them, and QGLWidget get the clicks otherwise?
I am using QGraphicsScene to display video. I have two modes in which two different videos are shown. I am using a QGraphicsPixmapItem and displaying the video on it. When I switch from one video to other it does not show the latest frame immediately. For 2 or 3 seconds the last seen image for that view is visible. I have tried using removeItem() and delete for removing the pixmap items every time I switch the views but it is not helping. Can some one suggest me how to solve this?
//Member variables
QGraphicsPixmapItem *m_pixItemZoomTrue;
QGraphicsPixmapItem *m_pixItemZoomFalse;
QGraphicsScene m_sceneZoomTrue;
QGraphicsScene m_sceneZoomFalse;
//Slot called on button click
void ZoomSelectionTrue()
{
//Remove the item from scene of ZoomSelectionFalse
m_sceneZoomFalse->removeItem(m_pixItemZoomFalse);
//Add item to the scene of ZoomSelectionTrue
m_pixItemZoomTrue = new QGraphicsPixItem();
m_sceneZoomTrue->addItem(m_pixItemZoomTrue);
//Rest code for adding pixmap to the pix item.
}
void ZoomSelectionFalse()
{
m_sceneZoomTrue->removeItem(m_pixItemZoomTrue);
m_pixItemZoomFalse = new QGraphicsPixItem();
m_sceneZoomFalse->addItem(m_pixItemZoomFalse);
//Rest code for adding pixmap to the pix item.
}
Thank You.
I have a QGraphicsView and a QGraphicsScene connected like this:
graphicsScene->setSceneRect(this->graphicsView->rect());
graphicsView->setScene(this->Scene);
Then I load an image and add it to the scene:
QPixmap pixmap;
pixmap.load(fileName);
pixmap = pixmap.scaled(this->graphicsView->size());
QGraphicsPixmapItem* item = this->Scene->addPixmap(pixmap);
Now, as described in the documentation, the image corner is at (0,0), which is not the corner of the graphicsScene. I know I can position the resulting pixmap by doing:
item->setPos(this->Scene->sceneRect().x(), this->Scene->sceneRect().y());
However, I can't seem to make sense of the coordinates of the rect's of the scene or the view. Can anyone explain how I would move the pixmap to the corner of the scene/view?
Thanks,
David
EDIT: Here is the full form constructor. The QGraphicsView was created in Qt Designer and is inside of a GridLayout:
Form::Form(QWidget *parent)
: QWidget(parent)
{
setupUi(this);
QGraphicsScene* scene = new QGraphicsScene;
scene->setSceneRect(this->graphicsView->rect());
this->graphicsView->setScene(scene);
QPixmap pixmap;
pixmap.load("image.png");
pixmap = pixmap.scaled(this->graphicsView->size());
scene->addPixmap(pixmap);
}
I also tried this:
QGraphicsScene* scene = new QGraphicsScene;
this->graphicsView->setScene(scene);
QPixmap pixmap;
pixmap.load("/home/doriad/glasses.jpg");
QGraphicsPixmapItem * item = scene->addPixmap(pixmap);
this->graphicsView->fitInView (item);
but the image appears tiny, rather than filling up the view like I would expect. Can anyone explain this?
The full project and image are available here: daviddoria.com/Uploads/qt/QPixmapPosition
Don't worry about scaling the pixmap yourself or even translating it, let the view do it for you.
Use graphicsView->fitInView(pixmap); but you should read the documentation for :
Qt's Graphics View Framework
void QGraphicsView::setSceneRect (QRectF )
void QGraphicsView::translate ( qreal dx, qreal dy )
void QGraphicsView::fitInView ( const QGraphicsItem * item, ... )
The way that QGraphicsScene and QGraphicsView interact is that you can have a single scene with at least one or more views.
A good example I like to think of is a zoomed in view of part of a map with a mini view of the entire map in the corner. There are two views, one of part of the map and one of the entire map, with one scene, the map itself.
So you put items in your scene and all the items in the scene are drawn relative in size to each other. The "scene rect" of your view, by default, scales to fit the items in the view until one unit in the scene is one pixel in the view or until it needs to zoom out to fit all the items in your scene.
If you call fitInView(someItem) it should scale your view of the scene so that the item specified fills it up and translates the view so that it is centered. If you need to translate or scale it more use the translate or scale functions in QGraphicsView.
When you are jumping between coordinate systems of your scene and view with your QRect's or QPoint's, use the helper functions: mapToScene and mapFromScene from QGraphicsView.
Try this:
QGraphicsScene* scene = new QGraphicsScene;
scene->setSceneRect(graphicsView->sceneRect());
QPixmap pixmap;
pixmap.load("/home/doriad/glasses.jpg");
pixmap=pixmap.scaledToWidth(this->graphicsView->width());
QGraphicsPixmapItem * item = scene->addPixmap(pixmap);
graphicsView->setScene(scene);
By default, the pixmap will be at (0,0) in the scene, and the scene will be at (0,0) in the view. QWidgets are sized by pixels. If you had a QGraphicsView the size of the screen and the resolution is 1440 x 900, you can position objects in that view from (0,0) or the top left corner of the screen, to (1440,900) the bottom right corner of the screen. Most QGraphicsItems are placed with reference to their top left corner. So placing a pixmap at (0,0) aligns the top left corner of the pixmap with the top left corner of the scene it's placed in. If your pixmap 'hangs off the bottom' of your view, try using:
pixmap=pixmap.scaledToHeight(this->graphicsView->height());
If you use the function:
this->graphicsView->fitInView (item);
The graphicsView will only scroll to the point where your item fits in the view.
I downloaded David's code and ran it two ways. Click the links to see the results.
1) with pixmap=pixmap.scaledToHeight(this->graphicsView->height());
2) with pixmap=pixmap.scaledToHeight(200);
I don't know enough to explain why this is happening, but I thought it would be a useful data point.
It turns out the problem was that the GraphicsView was in a layout. In my example, the resizing of the image was done in the Form constructor. Apparently this is before the layout takes its shape? I moved the code to a pushButton and when I click it the image is sized how I would expect.
I got the image to stay sized to the GraphicsView in the Layout by subclassing QGraphicsView and reimplementing :
class CustomGraphicsView: public QGraphicsView
{
Q_OBJECT
{
void resizeEvent ( QResizeEvent * event )
{
emit resized();
}
signals:
void resized();
}
Then I connect this resized() signal to a slot that simply calls this->View->fitInView (this->ImageToTraceItem);
David