Question about QImages

[SkripT]

Sorry but in the case of the scroll bars, the changes on the edited image in which moment are "updated" at the original image?

[high_flyer]

if you use the scroll bar option you dont need two images, only one, the one that you see, in the size it is at the moment, so when you edit it you are editing the image it self, no need to remember anything aside the original size.

[SkripT]

Well so here's the question that i make at the beginning of the thread: if you work only with the edited image and you apply recursive zooming to the image, it will lose quality, won't it?

[high_flyer]

yes it will as I said, you can't put the same amount of information in less "space".
When you scale down you loos information.

I thought your question was about the error you get from calculating your self the scaling, and my point was that you dont need to do it your self, but can let Qt do it for you.

[SkripT]

Hi, finally I have solved the problem. It's a little complicated to explain; in a little words the problem was that I was scaling at any "ratio" while all the other editors scale in order of 1/2, 1/3, 1/4, 1/5, .. Doing it in this way solves the problem of loss of precition. Thanks high_flyer

[Pieter from Belgium]

If you keep the original image, and paint it scaled when zooming, keep track of the viewing transformation and use the inverse transformation to paint _in the original image_, loss of information is avoided, regardless of the zoom factor. The zoom factor will only determine the quality/amount of information of the displayed image, not of the original one.

If the size of the images is not too large, and only modest zoomlevels up to something like 200% are needed, using QCanvasView (Qt3) might be a good idea. (No idea about Qt4.)

Pieter

[SkripT]

Hi Peter, the problem is that the mouse coordinates are from the scaled image, so they has to be translated to the original image with no less of precition. That's why not every scale could be correct.