Scaling a pixmap in a label

[anda_skoa]

scaled contents means the label will scale its content to fit the size of the label.

So if the label stays the same size, then the content stays the same size.

The last line in your function has no effect other than consuming CPU.
It creates a scaled version of the pixmap which you then immediately discard.

Cheers,
_

[GianluC93]

First of all, thank you for the reply.
I've understood what you said about the last line and the rest.
Can you tell me how can I scale the label to scale the pixmap inside it?
Maybe if you could paste some code you would really help me to understand how to do it, because I'm not very able and even if I've understood I don't know how to do this.
Thank you

[anda_skoa]

If your label is in a layout, you will have to set the label's fixed size to whatever you want it to be and use scaled contents with that.

Cheers,
_

[GianluC93]

Yes but I have to scale it many times, so I cannot set a size for the label, because it could change many times.
In fact this is only a first step just to understand how to scale it, because after I have to scale it connecting it to a vertical bar.

[anda_skoa]

I am afraid I don't understand.

You need a label with a target size so you set that size.
If the label has scaled contents set to true, it will scale its contents.

Cheers,
_

[GianluC93]

Maybe I'm not understanding what you're saying.
If you set the size of a label, the label will remain of that size?
I think (if I have understood) that if I set a size for a label and after I scale the pixmap,
the only thing that will scale will be the pixmap, not the label that has a fixed size. Am I wrong?
So my question is:

I have a mainwindow in which there are a label with a pixmap inside it, and near it a vertical bar that
should allow to zoom the image.
What should I do to scale my image when I 'move' (sorry, I don't know the correct word to explain it) the vertical bar?

If you could paste some code maybe it would be easier to understand.
Thank you

[anda_skoa]

If you set the size of a label, the label will remain of that size?

If you set its fixed size, yes.-

I think (if I have understood) that if I set a size for a label and after I scale the pixmap,

Why would you scale the pixmap?
I thought you wanted the pixmap to be fully displayed.

If you only want part of the image to be visible, then yes, scale the image, take the part you want to be visible, and let the label show it.

Cheers,
_

[GianluC93]

Maybe it's better to simplify the question.
I have an image (a pixmap in a label) and near it, a vertical bar. All of this is in a mainwindow.
Can you tell me how can I do to zoom a little my image using the vertical bar?

I don't want only a part of the image visibile, so (I suppose) I have to scale the image, but I don't know
how to do it because everytime I do it the label (that is fixed) doesn't allow the image inside it to scale.
So the image either remains of the same size (not scaling) or shows only a part of itself.
I want to show it entirely, not fully displayed but only a little larger.

[anda_skoa]

If the image is to be shown entirely, the label needs to have a size big enough to show the whole image.

In which case the easiest way is to resize the label appropriately and let it scale the pixmap.
See comment #4

Cheers,
_

[GianluC93]

Ok, so:

1) if I fix a size big enough to contain the image larger, if the image is not zoomed in that moment there will be empty spaces between the label and the image?

2)how can I connect this operation (scaling of the image) with the changes of the vertical bar?

Thank you

[anda_skoa]

1) if I fix a size big enough to contain the image larger, if the image is not zoomed in that moment there will be empty spaces between the label and the image?

Why would you want to set a size larger than the image?

2)how can I connect this operation (scaling of the image) with the changes of the vertical bar?

You connect to the bar's signal that indicates change of value and then calculate the target size.

Cheers,
_

[GianluC93]

Because you wrote "If the image is to be shown entirely, the label needs to have a size big enough to show the whole image."
I have to zoom it showing it entirely.

Can you show me some code to understand how to do the second point (vertical bar)?