I want to add a gif animated image in QLabel that add into the QGraphicsScene.
My code is here:
QLabel *lbl = new QLabel;
QMovie *mv = new QMovie(":/Images/sun.gif");
mv->start();
lbl->setWindowFlags(Qt::FramelessWindowHint);
lbl->setMask((new QPixmap(":/Images/sun.gif"))->mask()); // for create transparent for QLabel image
lbl->setMovie(mv);
lbl->setGeometry(10,10,10,10);
scene.addWidget(lbl);
but when I run that it will transparent with first frame of that gif and when the gif is running the photo will not show completely and it will run with transparented area in the first frame.
How can I solve that?
Thanks
The problem is that QLabel has window background by default. You're trying to remove it by do it incorrectly:
FramelessWindowHint doesn't make sense here, since it's only used for top level widgets, and a widget added to scene is technically hidden and doesn't have system window frame. This line should be removed.
setMask does exactly what you describe it does. Since QPixmap is not animated, its mask is the alpha mask of the first frame of animation. And you permanently apply this mask to the label. It's not surpising that it works, but obviously it's not what you want. This line should also be removed.
setGeometry line is incorrect. It prevents picture from being visible for me. Label has good size by default and there is no need for setGeometry. If you want to scale or move the item on the scene, you can do it after addWidget as for any other QGraphicsItem. E.g. addWidget(lbl)->setPos(10, 10).
The magic bullet you need is WA_NoSystemBackground. It disables background painting for QLabel completely. So, the full code would be:
QLabel *lbl = new QLabel;
QMovie *mv = new QMovie("c:/tmp/sun.gif");
mv->start();
lbl->setAttribute(Qt::WA_NoSystemBackground);
lbl->setMovie(mv);
scene.addWidget(lbl);
It works fine for me. However I consider it over-complicated. You should not use proxy widgets in scene unless necessary. You can easily add a movie using QMovie and QGraphicsPixmapItem and switching pixmaps as movie frames change. I wrote a convenient class for this:
Header:
class GraphicsMovieItem : public QObject, public QGraphicsPixmapItem {
Q_OBJECT
public:
GraphicsMovieItem(QGraphicsItem* parent = 0);
void setMovie(QMovie* movie);
private:
QMovie* m_movie;
private slots:
void frameChanged();
};
Source:
GraphicsMovieItem::GraphicsMovieItem(QGraphicsItem *parent)
: QGraphicsPixmapItem(parent), m_movie(0) {
}
void GraphicsMovieItem::setMovie(QMovie *movie) {
if (m_movie) {
disconnect(m_movie, SIGNAL(frameChanged(int)), this, SLOT(frameChanged()));
}
m_movie = movie;
if (m_movie) {
connect(m_movie, SIGNAL(frameChanged(int)), this, SLOT(frameChanged()));
}
frameChanged();
}
void GraphicsMovieItem::frameChanged() {
if (!m_movie) { return; }
setPixmap(m_movie->currentPixmap());
}
Usage:
QMovie *mv = new QMovie("c:/tmp/sun.gif");
GraphicsMovieItem* item = new GraphicsMovieItem();
item->setMovie(mv);
scene.addItem(item);
Related
How can I make the button go beyond the edge of QToolbar?
Below is the code as I create the toolbar:
mainwindow.h
class MainWindow : public QMainWindow
{
Q_OBJECT
public:
MainWindow(QWidget *parent = 0)
private:
QToolBar* _toolBar;
};
mainwindow.cpp
MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent)
{
_toolBar = new QToolBar;
QAction *actionAdd = new QAction(QIcon(":/images/add.png"), "", this);
_toolBar->addAction(actionAdd);
addToolBar(Qt::ToolBarArea::TopToolBarArea, _toolBar);
}
style.qss
QToolBar {
background: #018ac4;
height: 150px;
}
As said before, it is not possible to solve this correctly using QtWidgets.
However I see two options to visually create that effect:
Take the button out of the tool bar and add it to the main window instead, but do not add it to a layout. Usually i would say reposition it on resize events, but since it is in the top left, you might as well just call setGeometry() once on startup and not worry about it later. You probably have to add last, or call rise() though.
Make it look like the button sticks out, while it really doesn't. Make the toolbar as large as the button, but paint the lower part of the toolbar in the brighter blue, so that it looks like it is part of the widget below it.
It is not possible with widgets. A QWidget can not paint outside of its area. See this answer : https://stackoverflow.com/a/48302076/6165833.
However, the QToolBar is not really the parent of the QAction because addAction(QAction *action) does not take the ownership. So maybe the QMainWindow could paint your QAction the way you want but AFAIK this is not doable through the public API of Qt.
What you could do is use QML (but you would need to use QML for the whole window then).
I put a push button into the top-right corner of my main window menu bar:
QPushButton *pb = new QPushButton("Text");
pb->setSizePolicy(QSizePolicy::Preferred, QSizePolicy::Preferred);
QMainWindow *mainWindow;
mainWindow->menuBar()->setCornerWidget(pb, Qt::TopRightCorner);
The initial layout is fine. Sometime later, an asynchronous event changes the QPushButton's text to a longer string, but it gets clipped on the right.
I can see that the QPushButton's size changes when the string is updated. The QPushButton is displayed correctly if the window is resized. The problem appears to be getting the QMenuBar to recognize that the widget's size has changed.
This answer How to auto change QPushButton width and QMenuBar corner widget width when change text of button? suggests resetting the corner widget. I would rather avoid that, because my application's structure makes me jump through several ugly and awkward hoops to reset the corner widget after initializing.
The solution is simple. After updating the text of the button call menuBar()->adjustSize(); I have tested it in Qt5.5 and hope it will work for you.
You can use QWidgetAction as a horizontal menu widget:
class TestMenu : public QWidgetAction
{
public:
TestMenu(QObject *parent) :
QWidgetAction (parent)
{
}
virtual QWidget *createWidget(QWidget *parent)
{
QComboBox *combo = new QComboBox(parent);
combo->setFixedWidth(300);
return combo;
}
virtual void deleteWidget(QWidget *widget)
{
delete widget;
}
};
...
QMenu *menu = new QMenu();
menu->addAction(new TestMenu(this));
menuBar()->setCornerWidget(menu);
Here is another newbie to Qt.
What I need to do is to have a scrollable Area in the center of MainWindow, which displays images, and allows user to paint on the image.
Since I cannot add a QPixmap directly to a scrollable Area, I tried to create a subclass of QWidget, like below:
class Canvas: public QWidget
{
public:
Canvas(){
image = new QPixmap(480,320);
image->fill(Qt::red);
}
QPixmap *image;
};
Then I declared Canvas *c in the header file.
In the implementation, I wrote:
canvas = new Canvas;
setCentralWidget(canvas);
However, apparently this does not help to show up the QPixmap. I do not know what to do.
You don't need to subclass QWidget for this. QPixmap is not a widget, so it is not shown anywhere. You need to add your pixmap to some widget, this will work:
in header:
QLabel* imageLabel;
in cpp:
imageLabel = new QLabel(this);
QPixmap image(480,320);
image.fill(Qt::red);
imageLabel->setPixmap(image);
setCentralWidget(imageLabel);
I implemented QLabel much like Qt's ImageViewer example, except I use QGridLayout for positioning my widgets. I also implemented similar lines for scaling my QLabel using QScrollBar, but QLabel just doesn't scale like it should inside the QScrollArea. I am not sure if it is related to some kind of GridLayout management issue or something else. I have been reading everywhere and trying different things for 3 days now. Below I list the relevant portion of my code.
In my Viewer class constructor:
{
imageLabel1 = new QLabel;
imageLabel1->setSizePolicy(QSizePolicy::Minimum, QSizePolicy::Minimum);
imageLabel1->setScaledContents(true);
scrollArea1 = new QScrollArea;
scrollArea1->setWidget(imageLabel1);
scrollArea1->setWidgetResizable(true);
....
QGridLayout *centralLayout = new QGridLayout;
centralLayout->addWidget(scrollArea1, 0, 0);
...}
and my scaleImage method:
void Viewer::scaleImage1(int factor)
{
Q_ASSERT(imageLabel1->pixmap());
scaleFactor *= (1 + factor);
//imageLabel1->resize(scaleFactor* imageLabel1->pixmap()->size());
imageLabel1->pixmap()->toImage().scaled(scaleFactor* imageLabel1->pixmap()->size(), Qt::KeepAspectRatio, Qt::FastTransformation);
imageLabel1->adjustSize();
adjustScrollBar(scrollArea1->horizontalScrollBar(), factor);
adjustScrollBar(scrollArea1->verticalScrollBar(), factor);
imageLabel1->update();
}
My scaleImage1 function is a public slot, and it receives signal from a scrollbar that goes between 0 and 2 so that, into the scaleFactor, the imageLabel1 is designed to be capable of being zoomed in up to 3 times its original size. But when I run the code, I don’t observe the imageLabel becoming enlarged inside the QScrollArea, which I saw in the imageViewer demo. The imageLabel1 simply retains the original size as it is loaded and does not respond to the valueChange() of scrollbar.
I'd appreciate your advice/tips very much.
I think is because you set QSizePolicy::Minimum to the imageLabel, try with MinimumExpanding or other that better fit your needs.
I'm trying to animate the change of a QPixmap, inside QLabel.
I have MainWindow which holds several objects that derive from QScrollArea. Each of these holds a QLabel member.
Using mousePressEvent() I am able to replace the picture of each QLabel using setPixmap(). However, that simply switches the image in each QLabel, while what I would like to achieve is an animation where a new image slides over the existing one.
First I tried using a QTimeLine to draw the QPixmap on the QLabel myself (I've created a class that derives from QLabel for that, and wrote my own setPixmap()) but that didn't work. Next I tried using QPropertyAnimation but it can't construct on a Pixmap without me implementing a sub class for that as well.
Any thoughts or ideas are appreciated.
You will need a QObject with a property that can be animated, and generates the intermediate frames for the animation. An incomplete example:
class LabelAnimator : public QObject
{
Q_OBJECT
Q_PROPERTY(float progress READ progress WRITE setProgress)
public:
LabelAnimator(QLabel* label) : mProgress(0.0f),
mLabel(label),
mAnimation(new QPropertyAnimation(this, "progress", this)
{
mAnimation->setStartValue(0.0f);
mAnimation->setEndValue(1.0f);
}
void setProgress(float progress) {
mProgress = progress;
QPixmap pix = mOriginalPixmap;
int offset = - mLabel->width() * (1.0f-progress);
QPainter painter(&pix);
painter.paint(off, 0, mNewPixmap);
painter.end();
mLabel->setPixmap(pix);
}
void setPixmap(const QPixmap& pix) {
mOriginalPixmap = mLabel->pixmap();
mNewPixmap = pix;
mAnimation->start();
}
};
QLabel was never designed for such uses. Draw your QPixmaps inside a QGraphicsView, it is far more focused towards rendering effects and animations.