[O] Scaling of image previews in org-mode

[Johannes Brauer]

Hi!

If I insert a jpg in my org-mode document, I can preview it but not scale its 
width, like so:

Add the following code to my init.el file:
(setq org-image-actual-width nil)

Then insert this code in my document, where I want the image to appear:
#+ATTR_ORG: :width 20
[[./test.jpg]]

No matter which value I give for the width argument the image appears in the 
buffer always in its original size.

However, scaling for html export with #+attr_html works fine.

What is going wrong?

(Org-mode version 8.3.4 (8.3.4-99-ga8e4a3-elpa @ 
/Users/johannes/Library/Preferences/Aquamacs Emacs/Packages/elpa/org-20160704/)

Johannes