Change opacity of image continuously with slider position

[wakecarter]

I use markerPos in my interactive slider demo. You could take a look there.

PsychoPy Online Demos

If you have routines or experiments that are likely to be useful to others, please create a post in this thread, editing your post to add new demos so there is one post per creator. Ideally set your demos so they can be tested without consuming a credit (if you don’t have a site license) by adding a final routine that can’t end, disabling save incomplete results and adding a small number of credits. Please do not discuss the demos in this thread or create more than one post unless you have a la…