QImage inserted into QGraphicsTextItem looks fuzzy, when scaling QGraphicsTextItem

[stefan-koch]

What mean you with?:

The image the edit application gets is the same results as your scaling in the application?

Have you compared screenshots in post #15 and #19?

[high_flyer]

I lost you completely.

I suggested you try to scale the image with a graphics editing application the same way you do in your application to see if the result is the same.
If it is, then there is little you can do, probably you will have to scale to not so small size.
If the graphics editing application has a better visual result after scaling, then I don't know what the cause for the blur in the scaled image is.

[wysota]

test1.png is obviously scaled up, it is not 30px in height. Show us the result of scaling the image to 30px.

[stefan-koch]

look at post #17's code.

If I change the line
textItem->setScale(3);
to
textItem->setScale(1);

I get the following attached screenshot (test2.png). The images is now of good quality and should have 30 pix in height.

@high_flyer
scaled in a Graphics Editing Application (scaled image is tex.png - 3600 dpi - attached):
unscaled: graphicseditingapplication1.png
scaled smaller: graphicseditingapplication2.png
scaled up: graphicseditingapplication3.png

[wysota]

look at post #17's code.

If I change the line
textItem->setScale(3);
to
textItem->setScale(1);

I get the following attached screenshot (test2.png). The images is now of good quality and should have 30 pix in height.

That's exactly what I would expect. And if you scale it 3 times up it will be distorted. Are you expecting anything different?

You are aware that if you scale down an image 3 times and then scale it up three times you will not get the original image, right?

[stefan-koch]

That's exactly what I would expect. And if you scale it 3 times ...

That's the problem. How to solve it?
Look at OpenOffice if I insert a picture and zoom over 100 % in my example to 256% the picture looks good. (Note: I have maked the picture smaller in openoffice first - pick one edge with the mouse and move the mouse to make the image smaller)

see openoffice1.png (100% scaled), and openoffice2.png(256% scaled) for details.

My goal is to create a big image (example tex.png with 3600 dpi) and insert this scaled (smaller) into a QGraphicsTextItem, and scale the QGraphicsTextItem up and now QT should be intelligent, and knowledge about the big image (it should have the big image after scaling smaller) and now if I scale the QGraphicsTextItem up, I want that QT does automaticaly see that the QImage has a parent that is bigger and use the information of this, not use the information of the small scaled image.

[high_flyer]

That's the problem. How to solve it?

'That' (again one needs to guess what you mean) is not the problem.
The problem is the way you expect the scaling to work for you.

What open office does (probably) is show you scaled version of the original image each time, not a scaled version of the scaled image.
You need to do the same (that is how you solve it, what we are trying to explain to you in last 5-6 posts).
You need to have a living copy of the original image at hand, and scale it only down (from big to small), and not up (from small to big).
When you want to scale the small image up, you don't scale it really, you scale the original large image to the new scale factor you want the small image scaled up to.
When you scale - you always should scale the original image, not a scaled copy.

and scale the QGraphicsTextItem up and now QT should be intelligent, and knowledge about the big image

Qt is not "intelligent".
And its not Qt that has your image information, but a QImage object.
YOU have to supply the intelligence in your code, to use it.

[stefan-koch]

Yes now I have understand the problem. Thanks.

But how to forbid QT (QGraphicsTextItem) to automatically scale up the inserted (small) image?

Thanks

[wysota]

But how to forbid QT (QGraphicsTextItem) to automatically scale up the inserted (small) image?

Qt doesn't scale things up on its own. If it scales something up it is only because you tell it to. If you expect an image to be scaled up then put in a big image and scale down the item containing it. Then when the item is scaled up again, it will still use your original (non-scaled) image to calculate the result.

[stefan-koch]

Means that first scale up the QGraphicsTextItem and then insert the scaled image?

Qt doesn't scale things up on its own. If it scales something up it is only because you tell it to.

How did I this? Is it this line?: textItem->setScale(3);

[wysota]

Means that first scale up the QGraphicsTextItem and then insert the scaled image?

No. Put the original image, don't scale it yourself.

How did I this? Is it this line?: textItem->setScale(3);

This scales up, not down.

[stefan-koch]

This scales up, not down.

You mean that?: textItem->setScale(0.2);

What's with the text inside of the TextItem?

[stefan-koch]

Thank you high_flyer and wysota for your numerous present answers!

Note: The text and image inside of the QGraphicsTextItem should be independend of each other when scaling.

Is this possible with standard methods? Or is complex code needed? If yes, where to start?
Thanks.

[wysota]

It depends what you really mean by "independant". If they are really to be independant then they should not be the same item.

[stefan-koch]

independend should mean:
- the text and image is in one QGraphicsTextItem (not the text in a QGraphicsTextItem and the image in a QGraphicsPixmapItem)
- the image is sepaeratley scalable from the text, just both are in the same item

See screenshots snapshot1.png and snapshot2.png as example with openoffice

snapshot1.png shows you the image in openoffice inserted into the text ("As Character")
I think this is like a QGraphicsTextItem with a inserted QImage
snapshot2.png shows you the image in openoffice fixed to the page ("To Page")
I think this is like a QGraphicsPixmapItem fixed to the QGraphicsView and text in a QGraphicsTextItem (or anything outside of QGraphics... classes)

In my case the image should be fixed to the text. And the image should be zoomable.
Is this possible?

[wysota]

Your examples from open office probably treat the picture and the text as two separate items that are groupped together within a third item. You can follow the same pattern here. To be honest I don't see your problem. Open Office doesn't scale down your image anywhere, it operates on the original image everywhere and that's what you should do too.

[stefan-koch]

Hmm, can I do that with one item or need I three, too?
How would you proceed? Working again with QGraphicsTextItem or with QGraphicsItem, or with ...?

Look into attached screenshot.

[wysota]

I don't even know what you are doing I probably wouldn't use Graphics View here at all, I don't see any benefits.

[stefan-koch]

But if I use QGraphicsView, there is a problem

See last openoffice screenshot
teIMAGEst
What is if the user want edit the "te" before the IMAGE?
Would GraphicsView automatically set a new position for the IMAGE?

[wysota]

Why aren't you simply using QTextDocument with your own document layout (if needed)?