[PyQt] Best way to implement an Image Viewer?

[Vincent Vande Vyvre]

TP a écrit :
> I'm using Windows XP, Python 2.6.4, and PyQt 4.7.1.
>
> While trying out the example
> C:\Python26\Lib\site-packages\PyQt4\examples\widgets\imageviewer.pyw,
> I notice that the more I zoom into an 1553x2653 B&W PNG image, the
> longer it takes to display. This becomes unacceptably long (on the
> order of a few seconds) at the not so high 3x zoom factor.
>
> Intuitively, I would have thought it would be *faster* since the more
> I zoom in the fewer image pixels need to be displayed. I think what's
> happening is the entire QLabel widget is getting enlarged then
> cropped, rather than just displaying a sub-portion of the image:
>
>     def scaleImage(self, factor):
>         self.scaleFactor *= factor
>         self.imageLabel.resize(self.scaleFactor *
> self.imageLabel.pixmap().size())
>
> I want to create an app to help people explore various image
> processing operations. Fast & flexible image display is essential.
>
> Some features I like to have:
>
> * Zoom In/Out quickly. I can see zooming *out* being slower since more
>   image pixels would be involved. Once past the 1x zoom-in factor, I'd
>   rather have the pixels as raw as possible to avoid blurring edges
>   like the Image Viewer example currently does.
>
> * Compare transformations by having multiple views of images that are
>   synchronized as to pan position and zoom factor. Dragging the mouse
>   in any of the views should pan all the views.
>
> * Multi-screen support.
>
> I started off by modifying the PyQt4 Image Viewer example, but now I'm
> having second thoughts. Should I really be basing my Image Viewer on a
> QLabel?
>
> Should I instead be using a QGraphicsView (even though I'll probably
> only have a single image, not lots of 2D objects)?
>
> Maybe I should use a QGLWidget (I'd rather not).
>
> Or perhaps I have to write my own custom widget and draw using a
> QPainter object?
>
> Any tips or pointers to other PyQt-based Image Viewers would be
> appreciated.
> _______________________________________________
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>
>   
See attachement, it's an images viewer + zoom with QGraphicScene.

Before use, change the line 63

Vincent
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