QImage Help Pls

[munna]

Hi,

I have a widget of size, lets say (400,400). This widget i used to show an image. Also, this widget has a kind of box or frame of size (350,350). When user opens an image file, if the image size is bigger than the frame, then the part of the image that is outside the frame should look a little hazy whereas the part of the image that is inside the frame should be clear.

How can I do it?

Thanks a lot.

[jpn]

You could use QLabel for showing the image, then use custom painting to draw the frame and for example a transparent gray layer over the part which should be "hazy".

void ImageLabel::paintEvent(QPaintEvent* e)
{
    // let the label paint the image (setPixmap()) underneath
    QLabel::paintEvent(e);
 
    // init painter for custom drawing
    QPainter painter(this);
 
    // draw a frame over the image (black, 2 pixels wide)
    QRect frameRect(0, 0, 350, 350);
    painter.setPen(QPen(Qt::black, 2));
    painter.setBrush(Qt::NoBrush);
    painter.drawRect(frameRect);
 
    // calc clip region
    QRegion clipRegion(rect());
    clipRegion = clipRegion.subtract(frameRect);
    painter.setClipRegion(clipRegion);
 
    // draw a gray layour over the rest to make it look hazy
    painter.setPen(Qt::NoPen);
    QColor hazyColor(QColor(Qt::gray));
    hazyColor.setAlpha(100);
    painter.setBrush(QBrush(hazyColor));
    painter.drawRect(rect());
}

void ImageLabel::paintEvent(QPaintEvent* e)
{
    // let the label paint the image (setPixmap()) underneath
    QLabel::paintEvent(e);

    // init painter for custom drawing
    QPainter painter(this);

    // draw a frame over the image (black, 2 pixels wide)
    QRect frameRect(0, 0, 350, 350);
    painter.setPen(QPen(Qt::black, 2));
    painter.setBrush(Qt::NoBrush);
    painter.drawRect(frameRect);

    // calc clip region
    QRegion clipRegion(rect());
    clipRegion = clipRegion.subtract(frameRect);
    painter.setClipRegion(clipRegion);

    // draw a gray layour over the rest to make it look hazy
    painter.setPen(Qt::NoPen);
    QColor hazyColor(QColor(Qt::gray));
    hazyColor.setAlpha(100);
    painter.setBrush(QBrush(hazyColor));
    painter.drawRect(rect());
}

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PS. above code is written on the fly and is not guaranteed to work 100%

[munna]

Thanks a lot for the code. Is kind of working but not perfectly. I will look into it, and post back the working code.

Thanks.

[munna]

Another related help please.

How can I draw the image centered ?

What i mean is, if the image size is, lets say 500,500, then for the widget of size 400,400, the image should be drawn from -50 to 450 (x-scale) and -50 to 450 (y-scale), so that the center of the image co-incides with the center of the widget.

How can I do this ?

Thanks a lot.

[jpn]

I'm not sure if QLabel is capable of that, you might have to draw the pixmap yourself then.
At least you can make use of:
void QStyle::drawItemPixmap ( QPainter * painter, const QRect & rect, int alignment, const QPixmap & pixmap ) const [virtual]