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Month: March 2016

Take screenshot programmatically without root in Android

Take screenshot programmatically without root in Android

Here’s another post related to Android hacking.

One can find a lot of ways over the internet which will tell you how take the screenshot of your own app, and that’s like pretty easy too. That’s also allowed by the Android framework. Note that here I’m not talking about the screenshots you take (as a user) by pressing Power + Volume down keys (that screenshot is taken by the SystemUI which has extra privileges). Let’s talk about the case if you want to take screenshot programatically from your own app/service and want to cover the whole screen.

According to Android security, if you were to take the screenshot of the screen programmatically, the only views visible will be the ones created by your own app. It won’t contain the views created by any other app.

So, I present a way to take screenshots of other views from your own app programmatically. The trick here is to use android’s MediaProjection API. Also, do note that this sets the minimum API level to be 21.

What we’ll do is to render the Android’s display contents on a Surface using the MediaProjection API. But then the toughest part is to get the contents of this Surface and create a proper Bitmap out of that. There’s no direct way of doing that.

Over the past few days, I tried different ways and failed –

  1. Create the Surface from¬†the encoder, then attach a decoder to the encoder output, and create a Bitmap from the decoder’s raw output. (Didn’t work and I wasn’t surprised)
  2. Create an OpenGL texture, create a Surface using that texture, then whatever is drawn on the Surface will automatically get passed to the OpenGL texture, and then call glReadPixels() to get raw pixel data to create the Bitmap. (Should’ve worked but for some reason, I was just getting a green colored image)
  3. Then I tried Android’s ImageReader API and that finally worked out.

Enough of the bullshit, let’s start with some code.

First of all, we need to initialize the object of the ImageReader class.

Now, we need to pass this surface to the MediaProjection API. Please go through this demo code to learn how to create the object of MediaProjection class.

Implement the ImageReader.OnImageAvailableListener in your class and do the following –

Also, make sure you have the following permission in your manifest.

In case you’re too lazy and when everything setup for you, here’s a small library I created –