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.
Related
I am trying to add a QLabel with an image to my GUI at runtime, but the scaling is ignored and the image expands to its full size (which is larger than the screen), ignoring the size constraints and not scaling the contents correctly.
The image should be fit into the bottom, left side of the window, as my GridLayout describes here:
headerPnl= new HeaderPnl();
buttonPnl = new ButttonPnl;
mainContentPnl = new QStackedWidget;
mainLayout = new QGridLayout;
mainLayout->setMargin(0);
mainLayout->setSpacing(0);
mainLayout->addWidget(headerPnl, 0, 0, 1, 7);
mainLayout->addWidget(mainContentPnl, 1, 0, 10, 6);
mainLayout->addWidget(buttonPnl, 1, 6, 10, 1);
mainLayout->setRowStretch(0,1);
mainLayout->setRowStretch(1,2);
mainLayout->setRowStretch(2,2);
mainLayout->setRowStretch(3,2);
mainLayout->setRowStretch(4,2);
mainLayout->setRowStretch(5,2);
mainLayout->setRowStretch(6,2);
mainLayout->setColumnStretch(0,1);
mainLayout->setColumnStretch(1,1);
mainLayout->setColumnStretch(2,1);
mainLayout->setColumnStretch(3,1);
mainLayout->setColumnStretch(4,1);
mainLayout->setColumnStretch(5,1);
mainLayout->setColumnStretch(6,1);
this->setLayout(mainLayout);
The header goes across the top, the button panel goes along the right side, and the rest of the screen is changing depending on the workflow of the application (ie what buttons are pressed, etc).
When necessary, my GUI replaces the widgets and updates the GUI like this:
void MainWindow::setContentPane(QWidget *content){
mainLayout->replaceWidget(contentPnl, content);
contentPnl = content;
}
void MainWindow::setButtonPanel(QWidget *buttonPanel){
mainLayout->replaceWidget(buttonPnl, buttonPanel);
buttonPnl = buttonPanel;
}
void MainWindow::configureWelcome(){
QLabel *welcomeLbl = new QLabel;
welcomeLbl->setObjectName("welcomeLbl");
welcomeLbl->setPixmap(QPixmap(":/images/welcome.jpg"));
welcomeLbl->setScaledContents(true);
CustomWidget *welcomeWidget = new CustomWidget;
QHBoxLayout *welcomeLayout = new QHBoxLayout;
welcomeLayout->addWidget(welcomeLbl);
welcomeWidget->setLayout(welcomeLayout);
setContentPane(welcomeWidget);
CustomWidget *buttonPnl = createWelcomeButtonPanel();
setButtonPanel(buttonPnl);
}
How can I make this image fit inside the GridLayout properly? It seems like when adding widgets to a layout that has already been set, the GUI doesn't know how to handle the size constraints from the GridLayout. Replacing the buttons works fine, but adding an image does not.
Side question: I have been trying to stay away from a QStackedWidget, as this application is designed for a lower power system, and it doesn't make sense to me to create all the possible screens and add them all to a QStackedWidget when the application starts. Instead I would rather use the resources when necessary, and only create all the GUI elements when I need to (ie, when the right buttons are clicked). Does that make sense?
Did you had a QSizePolicy to the widget containing the QGridLayout? I suggest an horizontal and vertical QSizePolicy::Fixed.
In your first code segment add :
this->setSizePolicy(QSizePolicy::Fixed,QSizePolicy::Fixed);
I'm trying to show a rounded avatar QPixMap with a white border around it. However, I have no clue as to how I could add the border... Is it even possible?
This is the function I have to draw the avatar image.
void AccountDropDownMenu::setAvatar(
const QByteArray& bytes)
{
QPixmap new_avatar;
new_avatar.loadFromData(bytes);
new_avatar = new_avatar.scaledToHeight(40, Qt::SmoothTransformation);
QBitmap map(new_avatar.size());
map.fill(Qt::color0);
QPainter painter(&map);
painter.setRenderHint(QPainter::Antialiasing);
painter.setBrush(Qt::color1);
painter.setPen(QPen(Qt::white, 10));
painter.drawRoundedRect(
m_avatar_label->x(),
m_avatar_label->y(),
new_avatar.width(),
new_avatar.height(),
45,
45);
new_avatar.setMask(map);
avatar_label->setPixmap(new_avatar);
}
Update
Thanks to dtech I was able to get the desired output using the following updated function.... Although it's a bit pixly (the border).
void AccountDropDownMenu::setAvatar(
const QByteArray& bytes)
{
QPixmap new_avatar;
new_avatar.loadFromData(bytes);
new_avatar = new_avatar.scaledToHeight(40, Qt::SmoothTransformation);
QBitmap map(new_avatar.size());
map.fill(Qt::color0);
QPainter painter(&map);
painter.setRenderHint(QPainter::Antialiasing);
painter.setBrush(Qt::color1);
painter.drawRoundedRect(
QRectF(
avatar_label->x(),
avatar_label->y(),
new_avatar.width(),
new_avatar.height()),
40,
40);
new_avatar.setMask(map);
QPainter painter2(&new_avatar);
painter2.setRenderHint(QPainter::Antialiasing);
painter2.setPen(QPen(Qt::white, 1));
painter2.drawRoundedRect(
QRectF(
avatar_label->x(),
avatar_label->y(),
new_avatar.width(),
new_avatar.height()),
40,
40);
avatar_label->setPixmap(new_avatar);
}
In Qt you draw fills with a brush, but outlines are drawn with a QPen.
I haven't used QPainter in a long time, but IIRC, the default pen is zero width, which would explain why you aren't getting anything - you are not setting a pen.
Also, you don't need "another" rounded rectangle, you can apply fill and outline to the same geometry, as demonstrated in this answer.
Update:
Your updated code sets a mask, which sets an alpha channel. That cuts away from what you already have, it could not possibly add anything. You have to paint on the pixmap. Simply use new_avatar as the paint device - QPainter painter(&new_avatar); and get rid of the rest.
I have a program which functions similar to paint, and I have a change request as such:
Add a new function named mirror mode, in a mirror mode, the canvas is divided by left and right half. All the pictures that are drawn in one of the half should be mirrored to the opposite half.
I have added code such that the mirrored portion appears; however the original image does not appear to be drawn by QPainter. Is there a simple thing I'm missing to get QPainter to show both the mirrored image and drawn image. The relevant source code is as follows :
//
void ImageArea::paintEvent(QPaintEvent *event)
{
QPainter *painter = new QPainter();
painter->begin(this);
QRect *rect = new QRect(event->rect());
painter->setBrush(QBrush(QPixmap(":media/textures/transparent.jpg")));
painter->drawRect(0, 0,
mImage->rect().right() - 1,
mImage->rect().bottom() - 1);
painter->drawImage(event->rect(), *mImage, event->rect());
painter->setPen(Qt::NoPen);
painter->setBrush(QBrush(Qt::black));
painter->drawRect(QRect(mImage->rect().right(),
mImage->rect().bottom(), 6, 6));
painter->drawImage(event->rect(), *mImage, event->rect());
painter->end();
painter->begin(this);
QImage tmp(mImage->mirrored(true,false));
painter->drawImage(0, 0, tmp);
painter->end();
}
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 need to do something similar to QPainter::drawImage, but drawing a triangle part of the given picture (into a triangular region of my widget) instead of working with rectangles.
Any idea how I could do that, besides painfully trying to redraw every pixel?
Thanks for your insights!
If it is feasible for you to use a QPixmap instead of a QImage, you can set a bitmap mask for the QPixmap which defines which of the pixels are shown and which are transparent:
myPixmap->setMask(myTriangleMask);
painter->drawPixmap(myPixmap);
Here is another solution based on QImage:
MaskWidget::MaskWidget(QWidget* parent) : QWidget(parent) {
img = QImage("Sample.jpg"); // The image to paint
mask = QImage("Mask.png"); // An indexed 2-bit colormap image
QPainter imgPainter(&img);
imgPainter.drawImage(0, 0, mask); // Paint the mask onto the image
}
void MaskWidget::paintEvent ( QPaintEvent * event ) {
QPainter painter(this);
painter.drawImage(10, 10, img);
}
Mask.png is an image file with the same size as Sample.jpg. It contains an alpha channel to support transparency. You can create this file easily with The GIMP, for example. I added an alpha channel, changed all areas I want to have painted to transparent and all other areas to white. To reduce the size, I finally converted it to an indexed 2-bit image.
You could even create the mask image programmatically with Qt, if you need your triangle be computed based on various parameters.