To export to html an orgmode file which has links to multiple images, each of which has to have a given width, you can put something like #+ATTR_HTML: :width 800 above each image.
Is there a way to put this into the header of the file so that it will apply to all images without repetion?
You can define a local file variable in the file (that is a general customization method for emacs, not limited to Org mode). You have to find out the variable that controls that width setting: I do C-h v org--width TAB and look at the completions because I can never remember the names. In this case, the correct variable is org-image-actual-width: add the following at the bottom of your file:
# Local Variables:
# org-image-actual-width: 800
# End:
and try the export again. You will need imagemagick to be able to change the size of images like this.
Also read the doc string of the variable: there are nuances that the above does not capture - do C-h v org-image-actual-width RET.
