[SOLVED]convert const QImage & to QImage *
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I want to use this function:
@myLabel->setPixmap(QPixmap::fromImage(myImage));@In my header file I created @QImage *myImage;@
and, in cpp file I initialized it @myImage = new QImage(900, 900, QImage::Format_RGB32);@
It is necessary because the size of image is not always 900x900. The size is taken from a file.fromImage() function takes a parameter in const QImage & type, but in my program it must be QImage *, as I said above.
I used like this
@myLabel->setPixmap(QPixmap::fromImage(&myImage))@
this code does not give any build error, but during execution gives access violation error.How can I use it, or how can convert?
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I think you could read directly the file you want in the QImage using something like "this":http://doc.trolltech.com/4.7/qimage.html#QImage-9.
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because, I created it in header file and initialized in cpp file.
@QImage *myImage;@ // in header file
@myimage = new QImage(900, 900, QImage::Format_RGB32);@ // in cpp fileI tried to write
@QImage myImage;@ instead of @QImage myImage;@
but it gives error because of initialization.Is there any way of using it without pointer?
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[quote author="peppe" date="1312980799"]But why are you using a pointer to a QImage? And that code SHOULD give you an error, since the type passed to fromImage is "QImage **" which of course is not compatible with a "const QImage &".[/quote]
so the code must be then:
@
myLabel->setPixmap(QPixmap::fromImage(*myImage))
@A reference requires an object not a pointer.
@
class X* p; // is a pointer
@To dereference a pointer to an object, you must put a star in front:
@
class X {...};X* p;
X obj;
obj = *p;
X& ref1 = obj; // correct, reference to obejct
X& ref2 = p; // correct, reference to dereferenced pointer
X& ref3 = p; // error, as the reference is not a pointer!
X& ref4 = p; // correct, as the reference references a pointer to X --> modifying ref4 modifies p, not the object behind p!
@ -
yes, it is my fault.
I written this part as
@myLabel->setPixmap(QPixmap::fromImage(*myImage))@It does not give build error, it gives error during execution "Access violation"
It show me, the error is in that part:
@bool QCoreApplicationPrivate::sendThroughObjectEventFilters(QObject *receiver, QEvent *event)
{
Q_Q(QCoreApplication);
if (receiver != q) {
for (int i = 0; i < receiver->d_func()->eventFilters.size(); ++i) { // in this part
register QObject *obj = receiver->d_func()->eventFilters.at(i);
if (!obj)
continue;
if (obj->d_func()->threadData != receiver->d_func()->threadData) {
qWarning("QCoreApplication: Object event filter cannot be in a different thread.");
continue;
}
if (obj->eventFilter(receiver, event))
return true;
}
}
return false;
}@ -
Thanks guys,
the problem was not about the QImage.
I think it is an initialization problem, firstly I created the label and the image in the constructor,
after I filled the image and called the setPixmap function. It gave me error.
Now, I created the label and the image, and also called setPixmap function in the constructor.
After I filled the image and called setPixmap again. It works correctly.
