QImage deconstructor or delete / proper usage

[chrisbay90]

I have a serious memory leak due to what I beleive to be a new instance of QImage being created but not deleted in the memory every time a function is called. My code looks somewhat like this.

//myClass.cpp
 
// Public Function, called iterativly each frame
void myClass::updateAndPaint(int **arr, float  **arr2, int arrSize, int arr2Size, char type)
{
   // Do stuff here
   update();
}
 
// Private function
void myClass::paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget)
{
    QRectF rec = boundingRect();
    QImage image(width, height, QImage::Format_RGB32);
 
    // Do stuff here
    image.setPixel(x, y, thisPixel);
    // Do stuff here
 
    painter->drawImage(rec, image);
}

//myClass.cpp

// Public Function, called iterativly each frame
void myClass::updateAndPaint(int **arr, float  **arr2, int arrSize, int arr2Size, char type)
{
   // Do stuff here
   update();
}

// Private function
void myClass::paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget)
{
    QRectF rec = boundingRect();
    QImage image(width, height, QImage::Format_RGB32);

    // Do stuff here
    image.setPixel(x, y, thisPixel);
    // Do stuff here

    painter->drawImage(rec, image);
}

To copy to clipboard, switch view to plain text mode 

However if I make the QImage declaration global in the .h file like so

// myClass.h
QImage *image;

// myClass.h
QImage *image;

To copy to clipboard, switch view to plain text mode 

Then add this to the constructor

myClass::myClass(int height, int width)
{
    image = new QImage(width, height, QImage::Format_RGB32);
    // the rest of my constructor
}

myClass::myClass(int height, int width)
{
    image = new QImage(width, height, QImage::Format_RGB32);
    // the rest of my constructor
}

To copy to clipboard, switch view to plain text mode 

At any reference of the QImage object `image` in the paint function the compiler throws an error as such

error C2228: left of '.setPixel' must have class/struct/union

How instead should I be using QImage?

[Ginsengelf]

Hi, if you use a pointer, you need to use image->setPixel().
But your original code should not create a memory leak because the QImage is created on the stack and gets destroyed once the method myClass:aint() is left.

Ginsengelf

[d_stranz]

I'll make a pretty good bet that it is the "do stuff here" code that causes the memory leaks unless

image = new QImage(width, height, QImage::Format_RGB32);

image = new QImage(width, height, QImage::Format_RGB32);

To copy to clipboard, switch view to plain text mode 

this code also ended up inside the paint() method.