Thanks for your question. I had a look at your site; great furniture!
I poked around in a few of the product-specific galleries and it looks like the images that already have an alt text value are filled with something like the name portion of the image file, e.g., an alt text value of "TWO-COLOR-WOOD-FAN-CHAIR-6" for the image file "TWO-COLOR-WOOD-FAN-CHAIR-6-90x120.jpg".
You can use the Settings/Media Library Assistant IPTC/EXIF tab to add a Standard field mapping rule for your Alternate Text values. You can experiment with something like this:
- Leave the IPTC Value set to "-- None (select a value) --"
- In the EXIF/Template Value text box, enter a Content Template. For example,
template:[+name_only+] to use the name portion of the image file. You can use any of the values in the "Data sources for custom field mapping" section of the Documentation.
- Set the Priority dropdown to "EXIF".
- Set the Existing Text dropdown to "Keep". This will preserve any alt text values already in place.
Scroll down to the bottom of the screen and click "Save Changes" to save your work. You can apply the rule to all of your attachments by clicking the "Map All Attachments, Standard Fields Now" button or you can test it out on a few attachments by following the "Other Mapping Techniques" instructions in the "IPTC & EXIF Processing Options" section of the Documentation tab.
The "Existing Text/Keep" option satisfies your "only for the images that do not have alt text right currently" criterion. The "name_only" value is as close as MLA can come to your "product name [attached to], plus 1,2,3,4,5" criterion. You could use the title of the parent/[attached to] post or page, but there's no way currently to add a sequence number for the "1,2,3..." part you want.
That should get you started on filling in the alt text for your images. Let me know if you have any problems or further questions on this topic. Thanks for your interest in the plugin.