QGraphicsPixmapItem zooming in/out

Question

My application is for drawing shapes (polygons, points ..etc), I used QGrapichView and QGrapichScene and I added two different pixmap items (one for drawing, and the other one is 'legend' that will show the user how much the distance is), So far so good.

I implemented the zoom functionality and it is working fun. Still, my problem is: that when I zoom in/out the whole scene (the canvas QGraphicsPixmapItem and the legend QGraphicsPixmapItem) is affected and that is expected because I am re-scaling the QGrapichView while zooming (using the mouse wheel).

What I want is: I need only the canvas item to be zoomed in/out not the whole scene so that the legend will always be visible to the user.

Here is a snippet of the code that am using in zooming from this answer:

class PixmapScene(QGraphicsScene):
    pass


class Canvas(QGraphicsView):
    def __init__(self, scene):
        super().__init__(scene)
        self.scene = scene

        self.setHorizontalScrollBarPolicy(Qt.ScrollBarAlwaysOff)
        self.setVerticalScrollBarPolicy(Qt.ScrollBarAlwaysOff)

        background_color = QColor("#443b36")
        self.pixmap_item: QGraphicsItem = self.scene.addPixmap(QPixmap(780, 580))
        self.pixmap_item.setTransformationMode(Qt.FastTransformation)
        self.pixmap_item.pixmap().fill(background_color)

        self.legend = QPixmap(780, 580)
        self.legend.fill(QColor("#00ffffff"))

        p = QtGui.QPainter(self.legend)
        p.setPen(QPen(QColor("#0000FF"), 4))
        p.drawLine(35 * 5.1, self.legend.height() - 60, 35 * 8.9, self.legend.height() - 60)
        p.setPen(QColor("#c9c9c9"))
        p.setFont(QFont('Century Gothic', 14))
        p.drawText(35 * 5.5, self.legend.height() - 35, f'this text is from the other pixmap (legend)')
        p.end()
        self.scene.addPixmap(self.legend)
        self.zoom_times = 0

   def wheelEvent(self, event):
        zoom_in_factor = 1.25
        zoom_out_factor = 1 / zoom_in_factor

        # Save the scene pos
        old_pos = self.mapToScene(event.pos())

        # Zoom
        if event.angleDelta().y() > 0:
            if self.zoom_times == 6:
                return
            zoom_factor = zoom_in_factor
            self.zoom_times += 1
        else:
            if self.zoom_times == 0:
                return
            zoom_factor = zoom_out_factor
            self.zoom_times -= 1
        # here we are scaling the whole scene, what I want is zooming with keeping legend as it is
        self.scale(zoom_factor, zoom_factor)

        # Get the new position
        new_pos = self.mapToScene(event.pos())
        # Move scene to old position
        delta = new_pos - old_pos
        self.translate(delta.x(), delta.y())

please provide a [mre]. I also have the following doubt: I understand that you want to continue showing the legend (which is a rule apparently), but do you want it to scale or maintain a fixed size? — eyllanesc, May 17 '22 at 14:00
Thanks for your comment, i am making now a code example just needs some time. for now, I just want a maintain fixed size. — Uncle Bob, May 17 '22 at 14:16
Note: It is always advisable to provide the MRE so do not expect us to ask you for it, do it when publishing your post so we both save time. — eyllanesc, May 17 '22 at 14:32

QGraphicsPixmapItem zooming in/out

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