Hi. Now I've tried to search this but it's quite a specific thing, and I can't seem to word it right in Google. Anyhow, I'm looking to create a graph in Numbers (or any other programme that's not hugely expensive) where the is a picture at 50% opacity. When the number gets higher to the target number, the picture gradually starts getting opaque-er. For example, if my target number was 400 and I had 100 as the value, the picture would be 25% opaque and 75% at half the opacity. Anyone know how I could do this?