I've to output few points in an interactively selected region of an image. I'm not familiar with PyQt to select the appropriate elements for the task. Please suggest the right way to do it. Currently, this is what I intend to do :

Load the image. 

Use QImage (QPixMap?) to display the image.

Select a rectangular region in the image.

Use QRubberBand to select the region.

Draw a grid in the region.

Use QLines?

Make the grid points (interesctions) selectable.

No idea.


Any pointers to snippets using the required classes will be greatly helpful. Thanks !
Use QGraphicsScene and QGraphicsView to display your scene. 

Use scene->addPixmap to add the image. 
Use QRubberBand to select the region as you said. 
Use view->mapToScene to convert viewport coordinates obtained from QRubberBand to the scene coordinates.
Add lines using scene->addLine
Add small circle items to lines intersection points using scene->addEllipse. This function returns QGraphicsEllipseItem* object. You should use circles with (0, 0) center. Use item->setPos to move each circle in the proper place.
Use item->setFlag(QGraphicsItem::ItemIsSelectable) to make circle items selectable. You can now select items with mouse clicks.
Use view->dragMode(QGraphicsView::RubberBandDrag) if you want to enable items selection using automatic QRubberBand. 
Use QGraphicsScene::selectedItems to obtain selected items. You can then use item->pos() to obtain items positions.
How to select an area and fill it with a grid in PyQt?