I am creating an accessible PDF which includes some images with alt text, but when I test them using VoiceOver, nothing happens (i.e. the images are skipped).
I have designed the PDF in InDesign CC. I have gone through 'Object Export Options' and written alt text for relevant images, and labelled any irrelevant ones as 'artefacts'.
I export as an Interactive PDF, with these two options ticked: 'Create Tagged PDF' and 'Use Structure for Tab Order'.
In Adobe Acrobat accessibility check, the alt text is marked as 'passed'. When I look at the Content pannel, the images with alt text are appearing as 'Container <Artifacts>' and a series of Paths. When I look at the Tags pannel, the images aren't in the list at all. I have followed these instructions here but doesn't seem to help: https://helpx.adobe.com/acrobat/using/create-verify-pdf-accessibility.html
To view it, I am opening in Preview and viewing at Single Page view, and VoiceOver reads the text perfectly, but it ignores the images.
Well, the fact that they are artefacted should give us a clue. Make sure you just create the Alt Text and check in the other tab of the Object Export Options that it is NOT set to artefact or the Alt Text will be, of course, artefacted as well. Be sure to check if you see the images in the Tags tree (not the Content tree with containers), they should appear there (if they are anchored in the text they appear in an enclosed p-tag).
By the way: Voiceover in Preview does not read out aloud as it should, neither does Acrobats build-in 'voice'. You should test with dedicated software that understands the tag-structure, choose Jaws and check it with that. Forget about Preview, very bad app.