Transparency on iOS

Before I get too carried away, is this possible on iOS?

I need an HTMLviewer with a rectangle over it (bring to front, Z-, towards the user).

The rectangle can be anything (canvas, image, button, don’t care), as long as I can vary the transparency.
It would be ok to load a png for the whole area, but color change would be easier in a control.

Reading the forums, it looks like this can be done on desktop. Will it work on iOS?


Why don’t you tell us what your end goal is for the user to experience, this sounds quite convoluted (you don’t care what the object is you place over the HTML Viewer?)

If we know what you’re actually trying to accomplish, we might be able to help you reach your goal.

Looks like a canvas would be the winner.

On Desktop, it will probably work with Mac, but I doubt very much one can mask the Windows HTMLViewer with a simple Canvas. A window will be required. A semi transparent window in Windows may be more complex, though.

The user will see the website of their choice through a slot in between two variably-transparent masks, so they only see one line of text highlighted.

Target platform is iPad; desktop is already a separate app with Z priority which cannot be done on mobile so I suggested an app with a view.

Object is to be able to change url, scroll page behind and vary transparency.

There is a desktop app which has been around for years.
This is a proof of concept for a friend that works with reading-challenged kids and adults and has the patent on the reading mask.
If it’s simple I’ll buy Xojo iOS as I’d like to get back into it.

I have a baby-reading app ( that has found some application in adult literacy, that’s how I got involved.

If you don’t mind installing a free library: iOSLib in AppleLib supports alpha for all controls, and I am sure iOSKit has a similar feature too. Sounds like UIVisualEffectViews could be an option for you too.