CODEWITHSUNDEEP
c++qmlqtquick2qt5.3
user2703750
user2703750

Reputation: 141

QQuickImage convert to QImage

I've been using QZXing to decode QR code, my QML looks like this

Image{ 
    width:300
    height:300
    id:imageToDecode
    source:"qr.jpg"
    cache: true
}

and when i pass it into C++ file, it has to be converted into a QImage type, in the code the original coder wrote like this

QGraphicsItem *item = qobject_cast<QGraphicsItem*>(imageObj);

and then use QGraphicsItem to construct a QImage,however this will always return 0 after conversion, since QGraphicsItem does not inherit QObject

straight conversion like

QImage*item = qobject_cast<QImage*>(imageToDecode);

will not work for same reason,ive been using

imageObj->inherits("objectName");

to test which one it can be converted to, but there is none i can find my point is to convert QML Image into QImage.

Upvotes: 4

Views: 2788

Answers (2)

Charles Thomas
Charles Thomas

Reputation: 1005

I found something that may (or may not) be a workaround to this issue.

Within the Image that is assigned the preview source, I call grabToImage() in order to create a QQuickItemGrabResult object and then in C++, I call the image() function on that object. It seems to work.

QML

Image {
  id:imageToDecode
  MouseArea {
    anchors.fill:parent
    onClicked: parent.grabToImage(function(result)
      decoder.decodeImageQML(result); })
    }
 }

C++

QImage ImageHandler::extractQImage(QObject *imageObj,
                     const double offsetX, const double offsetY,
                     const double width, const double height)
{
    QQuickItemGrabResult *item = 0;
    item = qobject_cast<QQuickItemGrabResult*>(imageObj);
    QImage item_image(item->image());
    ....
}

Upvotes: 1

astre
astre

Reputation: 807

If you are using Qt5 or greater and QtQuick 2.0 or greater you can't render the Image element to QGraphicsItem or anything related to QGraphics since from Qt5 the backend for QML is scenegraph and not QGraphics. So now going forward with Qt5.3 and you if access the Image element in C++, it will be casted to a QQuickImage internally, but still you can't extract image from Image element since QQuickImage has not been made public yet. Ref. http://qt-project.org/forums/viewthread/32767

The solution they have proposed for now is to use QQuickImageProvider.

Upvotes: 2

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