Feature request: Support for changing image() transparency

This was requested on ZenDesk, so I am putting the report here.

They would like a way to change the transparency of an image. Processing does that via tint() but we could choose to do that via an extra parameter to image(), if we did want to add support for this.

Currently low priority based on demand.

Start by locating the live editor's image() API and its rendering path. Review the requested Processing-style tint() behavior and decide whether transparency belongs in tint() or as an image() parameter; done means a defined API behavior and support for changing image transparency.

Written by the indexing model from the issue text.