Transparent color in Qt

Qt Enthusiast

I am just asking . This is my legacy code

QVariant myModel::data(const QModelIndex& index, int role) const {
switch (role) {
case Qt::DecorationRole:
if (index.column() == 1) {
myInst inst = getInstance(index);
QColor sc = getColorForInstance(index,inst);;
if(sc.isValid()) {
QPixmap cellPixmap(QSize(10,10));
cellPixmap.fill(sc);
QIcon icon(cellPixmap);
return icon;
}
}
break;
}

QColor myModel::getColorForInstance(const QModelIndex& index ,Myinst inst) const {
QColor sc;
i f (condition1) {
// transparent color
return sc;
}

   if(condition2) {
        sc = QColor(Qt::red)
      return sc
    }

}

there alpha option in QColor constructor for transparency , is there any way I can use the same in above code

Qt Enthusiast

Hi
We tried to create a transparent image , but it is not giving me proper results .

QPixmap pix(500,500);
QPainter *paint = new QPainter(&pix);
paint->setPen(QColor(255,34,255,255));
paint->setBrush(QColor(255,34,255,50));
paint->drawRect(15,15,100,100);
delete paint;

Can some one guide me for that

mrjj

so what do u get?

Qt Enthusiast

I am some black image . I want a trasparent color image with a boundary colored

Qt Enthusiast

I tried this also

QPixmap cellPixmap(QSize(10,10));
QPainter *paint = new QPainter(&cellPixmap);
paint->setPen(Qt::transparent);
paint->setBrush(Qt::transparent);
paint->drawRect(10,10,10,10);
delete paint;
QIcon icon(cellPixmap);
return icon;
I am still getting black image .

What is purpose of setPen and setBrush

mrjj

hi
can you try
paint->setPen(QColor(255,0,0));
paint->setBrush(QColor(255,0,0));
and tell me if its red.
Else something else is wrong.

also u say
QPixmap cellPixmap(QSize(10,10));
paint->drawRect(10,10,10,10);

which means u draw OUTSIDE your image.

the image is only 10x10.
and u tell rect to start at 10,10

Qt Enthusiast

With this code

  QPixmap cellPixmap(QSize(10,10));

QPainter *paint = new QPainter(&cellPixmap);
paint->setPen(QColor(255,0,0));
paint->setBrush(QColor(255,0,0));
paint->drawRect(0,0,10,10);
delete paint;
QIcon icon(cellPixmap);

I cannot see any thing . Could you correct my code

mrjj

it looks fine except no need to new it

QPainter paint(&cellPixmap);
paint.setPen(QColor(255,0,0));
paint.setBrush(QColor(255,0,0));
paint.drawRect(0,0,10,10);

mrjj

void MainWindow::on_pushButton_3_released()
{
    QPixmap pixmap(100,100);
    pixmap.fill(QColor("transparent"));

    QPainter paint(&pixmap);
    paint.setPen(QColor(255,0,0));
    paint.setBrush(QColor(255,0,0));
    paint.drawRect(0,0,10,10);

    ui->label->setPixmap(pixmap);
}

This does produce red rect for me.
(testing with QLabel)

Qt Enthusiast

but how to get transparent color with a boundary without any solid fill . Let me know

[link text](link url http://doc.qt.io/qt-4.8/qpainter.html#drawRect-3 , image with square with no fill just the boundary

mrjj

@Qt-Enthusiast
paint.setBrush(QColor("transparent"));

gives me