android Accessibility screen magnifier

Question

I would like to create an Android Accessibility Application/Service. This Accessibility app would be able to magnify any screen image produced by any application resident on the android device.

for example, I would like to be able to magnify...

1. the home screen
2. Settings menu and sub menus

I would like to magnify Text and images/icons etc..

I've googled and searched the android dev docs for hints/tips/ideas.

Sadly I've hit a dead end.

Is this type of Accessibility application impossible to develop on Android?

Answer 1

Jellybean - Android 4.2 - apparently has this functionality built-in - see this release article detailing new features in Jelly Bean: "Accessibility: Enable screen magnification to easily zoom or pan the entire screen to get a closer look. Visually impaired users can now enter full-screen magnification with a triple-tap on the screen"

Typically on mobile operating systems these features are built into the OS, and not something that a 3rd party can write; partly for security reasons (a magnifier would have access to the graphic output of other apps, so could in theory send screenshots containing sensitive information back to base on the sly) and partly because magnification is complex, in that it involves interfering with normal video output and also with touch input (touch input has to be scaled in the inverse way that the original graphics area, so that touching a magnified button goes to the right place).

There may be a way of doing this if you are prepared to root your device and poke around at the OS/driver level, but that's not going to help much if you want an app you can put in the store.