problem with exporting an object

When I export a 4 inch by 2 inch object in Draw as a png picture the result is the entire Draw page. How do I limit the file to the object as defined by the selection (similar to a PowerPoint save as picture)

First convert To Bitmap. Now the context menu should show a (working) Save option.

(additional method to @Lupp’s)

the result is the entire Draw page

Select the object, then go to dialog File menu > Export … [x] Selection (other steps are self explaining).

Does not work. I select the object (4 x 2 inches), export to png and the exported image is of the entire 8.5 x 11 inch page. I need a 4x2 inch image. (Mac using OS X 10.11.6 Libreoffice 6.1.5)

Please post any reply to an answer (or related supplementary question ) as a comment on that answer. Any completion (or additional information) to your original question please post by editing that question and appending what needed.

If you insert a png as an image and then resize the shape created as a kind of container for the png, the picture will be displayed with the new size, but not changed on the level of the embedded file. Otherwise the context menu of the shape couldn’t offer the choice to set the original size again.
You will (so I think) need to first convert to meatfile, and then to bitmap again. If you now save it (as a png again probably) you should get shown the current size - and offered to change it.