Mirroring a Pixmap Item around an axis

Giuseppe97

In a game I'm developing I have a Mario class :

class Mario : public QGraphicsPixmapItem

and when right arrow key is pressed I want to change the texture of Mario item from the first picture to the second one below
(every square in the picture is one pixel):

In order to achieve this, my idea was to mirror the first texture in the picture above around the green axis . I actually have tried to express this idea in the following code :

if (e->key() == Qt::Key_Right)
	mario->setPixmap(mario->pixmap().transformed(QTransform().scale(-1, 1)));

but I obtain this situation :

What is a way to achieve a mirroring of the texture around an axis which is not the 'Z' one but the green one you see in the first picture I have posted?

SGaist

Hi,

What do you get if you use the mirrored method ?

Giuseppe97

@SGaist Hi. That method applies to a QImage and in my case I have tried to apply it to the pixmap (returned by pixmap() )of the item but there is such an item because a QImage is a Qpixmape but not viceversa. Am I right?

SGaist

I am not sure I am following you because your transformed call is also applied directly to your QImage.

Giuseppe97

@SGaist In this line of code

mario->setPixmap(mario->pixmap().transformed(QTransform().scale(-1, 1)));

where is QImage? I haven't understood where I should apply the mirrored method

SGaist

My bad ! I mixed both classes.

What I had in mind was to apply the mirroring or the original QImage and then load it in the item,

Giuseppe97

@SGaist Do you have any other idea? I can't figure out by myself and I was hoping someone with more experience than me would have had some hints.

SGaist

Well, why not use the setTransform method if your item directly ?

Giuseppe97

@SGaist ok so something like this

mario->setPixmap(mario->pixmap().transformed(setTransform()));

and how can I achieve the mirroring towards that green axis?

SGaist

No, I suggested to transform the item not it's content hence the link I provided to the QGraphicsItem::setTransform method.

Giuseppe97

@SGaist OK , now I am following you. So according to you in order to mirror mario ,through setTransform method, I should do
something like:

mario->setTransform()

and I should chain two consecutive transformations (e.g TRANSLATE + SCALE(-1,1) ) by passing an opportune matrix to the setTransform method. Am I right?

If so, could you show me through a small piece of code how to chain a translation plus a scale operation?

SGaist

Did you already read the Graphics View Overview in Qt's documentation ?