I have a MainWindow with a QLabel and a pixmap. I want to make it transparent (or less opaque)
I am using the following code below.
ui->label->setAttribute(Qt::WA_TranslucentBackground);
ui->label->repaint();
However it does not seem to work. The image looks the same without any changes. I also tried to use to the following statement:
ui->label->setStyleSheet("background-color: rgba(255, 255, 255, 10);");
Unfortunately, this does not seem to work either.
Anyone knows how can I make an image transparent or make it less opaque?
Thank you for your time.
If your image isn't transparent as it is and you want it to be, you can do something like this:
QLabel *l = new QLabel(this);
QImage image(":/img/myimage.png");
QPainter p;
p.begin(&image);
p.setCompositionMode(QPainter::CompositionMode_DestinationIn);
p.fillRect(image.rect(), QColor(0, 0, 0, 50));
p.end();
l->setPixmap(QPixmap::fromImage(image));
You can apply QGraphicsOpacityEffect to a label to adjust it's opacity.
You can use method fill, example:
pixmap = QPixmap(width_size_in_pixels, height_size_in_pixels)
pixmap.fill(Qt.transparent)
Related
Is it possible to make the background of the button transparent, but at the same time to add an icon?
As I understood I should use:
button -> setStyleSheet("background-color: rgba(255, 255, 255, 0); ");
It works fine, but I want to add an icon too. I have a nice window's background and want to see it through my buttons, but buttons should have icon - black arrow.
It is possible using Qt 6 C++. I found a way how to do it:
QPixmap buttonImage("/*path*/");
QIcon buttonIcon(buttonImage);
// make the button transparent
button->setStyleSheet("background-color: rgba(255, 255, 255, 0); ");
// add icon
button->setIcon(buttonIcon);
So I am trying to change only the background color of my MainWindow. When I try to do this using this->setStyleSheet("background-color:black;"); for example it changes the background of everything: child widgets, QTextBoxEdit background, everything.
Is there a way to only change the background of just the main window?
As you know, every QMainWindow has a central widget and by default is named centralwidget.
So the best way of solving this issue is changing the background for that widget.
It's pretty simple when we use a style sheet. In this case would be the following one:
#centralwidget {
background-color: rgb(0, 0, 0);
}
you can use Qt class name before QSS, like
QMainWindow { background-color: rgb(0, 0, 0);}
in your example QMainWindow > QWidget { background-color: rgb(0, 0, 0);} maybe better.
please see http://doc.qt.io/qt-4.8/stylesheet-syntax.html for more information
I want to draw 1 digit on the screen by the graphic framework classes. I want the fill approach of '1' to be something like
(source: qt-project.org)
but the brush of my drawn '1' is just like a yellow SolidBrush by the below code (an ugly bold yellow '1'). Can you help me what's wrong with it?
QGraphicsSimpleTextItem digit_1 = new QGraphicsSimpleTextItem;
digit_1->setText(QString::number(1));
digit_1->setPen(QPen(QColor("black")));
QLinearGradient gradient(digit_1->boundingRect().topLeft(),
digit_1->boundingRect().bottomRight());
gradient.setColorAt(0, Qt::white);
gradient.setColorAt(1, Qt::yellow); // yellow is for example
QBrush brush(gradient);
brush.setStyle(Qt::BrushStyle::LinearGradientPattern);
digit_1->setBrush(brush);
digit_1->setFont(QFont("courier", 35, QFont::Black));
Thanks in advanced.
Your issue most likely comes from the fact that you're basing your gradient's "area" on the bounding rect of your item before you set the font size to something much larger than the default.
The bounding rect you're getting is thus much smaller than your actual bounding rect. Since the default spread method is padding, you're seeing most likely just one color (or not enough of the gradient for it to be actually visible).
So move your setFont call to the top, before you create the gradient. You can drop the setStyle on your brush, that's determined automatically from the gradient. (In fact, you can drop that brush entirely and use the gradient in setBrush.)
With the way you set up the gradient, you'll get a "diagonal" gradient. If you want it from top to bottom, use the top left and bottom left points instead.
Demo
#include <QtGui>
class W: public QGraphicsView
{
Q_OBJECT
public:
W(QWidget *parent = 0)
: QGraphicsView(parent)
{
QGraphicsSimpleTextItem *item = new QGraphicsSimpleTextItem;
item->setText("Stack Overflow");
item->setPen(QPen(Qt::red));
item->setFont(QFont("courier", 60, QFont::Bold));
QLinearGradient lgrad(item->boundingRect().topLeft(),
item->boundingRect().bottomLeft());
lgrad.setColorAt(0.0, Qt::red);
lgrad.setColorAt(1.0, Qt::yellow);
item->setBrush(lgrad);
QGraphicsScene *scene = new QGraphicsScene;
scene->setBackgroundBrush(QBrush(Qt::black));
scene->addItem(item);
setScene(scene);
}
};
I'm using PyQt, and I've loaded an image from disk into a QPixmap. I've also created a mask, using:
self.mask = QImage(self.image.width(), self.image.height(), QImage.Format_Mono)
self.mask.fill(0)
I'd like to combine the two for display, such that any pixels colored black in the mask are drawn in translucent red over the image when I render it.
I've created a custom widget, that renders the image in the paint event like so:
def paintEvent(self, event):
p = QPainter(self)
r = event.rect()
p.drawPixmap(r, self.image, r)
This works fine. What I'm less clear on is how to take the data in the mask and paint a translucent red only over those pixels in the destination image.
I've tried turning the mask into a clipping region, like this:
mask = QPixmap.fromImage(self.mask.createMaskFromColor(self.mask.color(0)))
p.setClipRegion(QRegion(mask))
color = QColor(255, 0, 0, 128)
p.setPen(Qt.NoPen)
p.setBrush(QBrush(color))
p.drawRect(r)
... but it doesn't draw anything (and draws a translucent red box over the whole image if I don't call setClipRegion).
I also tried creating the mask as a QImage.Format_ARGB4444_Premultiplied, and using transparency. And while this does work, and I can edit the mask in my program (and verify that some portions of the mask are transparent and some portions are opaque) the self.mask.createAlphaMask() method returns a solid white rectangle.
Do the "create mask" methods actually do anything?
Either change your mask's design or create a new QImage based on your mask. Then draw the QImage on the destination. It is not only a method that works, but also a method that is faster than drawing single pixels or sth. similar. I tried several ways and this was the fastest so far (on a QGLWidget).
The idea is that you encode the transparency, and also the non-marked pixels, in the QImage directly, like this:
QImage dest(<width>, <height>, QImage::Format_ARGB32);
dest.fill(qRgba(0, 0, 0, 0));
for (int y = 0; y < <height>; ++y) {
QRgb *destrow = (QRgb*)dest.scanLine(y);
for (int x = 0; x < <width>; ++x) {
if (<should be marked>)
destrow[x] = qRgba(255, 0, 0, 127);
}
}
painter.drawImage(0, 0, dest);
For reference, take a look at the code here:
https://sourceforge.net/p/gerbil/svn/60/tree/trunk/gerbil-gui/bandview.cpp#l59
I want to show difference between a trimed clip and non trimed clip in my video editor application, i.e. I want to add a small film image on my thumbnail for a trimed clip. How can I do this?
It would be just to show the difference between an image and a video in our gallery application.
How to add an image on the top of another one in Qt?
Open the QPainter on the bottom image and draw the top image using its drawPixmap()/drawImage() methods.
QPixmap base, overlay; // come from your code
{
QPainter painter(base);
painter.drawPixmap(100, 100, overlay);
}
If your overlay contains an alpha channel (e.g. fancy PNG icon) and your base image does not, you should create a new QPixmap with an alpha channel and draw both images into it:
QPixmap base, overlay; // come from your code
QPixmap result(base.width(), base.height());
result.fill(Qt::transparent); // force alpha channel
{
QPainter painter(&result);
painter.drawPixmap(0, 0, base);
painter.drawPixmap(100, 100, overlay);
}
QPixmaps and QImages can be used interchangeably, although not all combinations give good performance).
If it's just about showing an image above another, then you could also go with this answer.
QGridLayout *layout = new QGridLayout(widget);
Pixmap base, overlay;
QLabel *background = new Label();
background->setPixmap(&base);
QLabel *lOverlay = new QLabel();
lOverlay->setPixmap(&overlay);
//label gets positioned above textBrowser and is an overlay
layout->addWidget(background, 0, 0, Qt::AlignLeft | Qt::AlignTop);
layout->addWidget(lOverlay, 0, 0, Qt::AlignRight | Qt::AlignBottom);
Of course then the QPixbuf of the background doesn't contain the QPixbuf of the overlay-image, but it only appears to do.