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Alpha Movie

Alpha Movie is an Android video player library with alpha channel support.

Video Player uses OpenGL to render video and apply shader that makes alpha compositing possible. The player encapsulates MediaPlayer and has its base functionality. Video stream is displayed by TextureView.


Gradle Dependency

jCenter License

The easiest way to start using Alpha Movie is to add it as a Gradle Dependency. The Gradle dependency is available via jCenter. Please make sure that you have the jcenter repository included in the project's build.gradle file (jCenter is the default Maven repository used by Android Studio):

repositories {
    jcenter()
}

Then add this dependency to your module's build.gradle file:

dependencies {
    // ... other dependencies
    compile 'com.alphamovie.library:alpha-movie:1.2.1'
}

Getting Started

Add AlphaMovieView into you activity layout:

<com.alphamovie.lib.AlphaMovieView
    android:id="@+id/video_player"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"/>

Next you need to initialize the player. In your Activity class add:

public class MainActivity extends AppCompatActivity {

    private AlphaMovieView alphaMovieView;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        alphaMovieView = (AlphaMovieView) findViewById(R.id.video_player);
        alphaMovieView.setVideoFromAssets("video.mp4");
    }

    @Override
    public void onResume() {
        super.onResume();
        alphaMovieView.onResume();
    }

    @Override
    public void onPause() {
        super.onPause();
        alphaMovieView.onPause();
    }
}

In this code snippet we load video from assets specifying filename video.mp4:

alphaMovieView.setVideoFromAssets("video.mp4");

Video can also be set by Url, FileDescriptor, MediaSource and other sources.

You need to add alphaMovieView.onPause() and alphaMovieView.onResume() in activity's onPause() and onResume() callbacks. Calling these methods will pause and resume OpenGL rendering thread.

Video playback can be paused and resumed using alphaMovieView.pause() and alphaMovieView.start() methods.


How it works?

Alpha Movie player uses OpenGL to render video with a shader attached to gl renderer. This shader modifies each pixel of video frame. By default it converts green color to transparent.

So default alpha channel color is green. This color can be changed to any rgb color by adding xml attribute alphaColor:

<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:custom="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <com.alphamovie.lib.AlphaMovieView
        android:id="@+id/video_player"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        custom:alphaColor="#ff0000"
        custom:accuracy="0.7"/>
</FrameLayout>

In the code snippet above we set custom:alphaColor="#ff0000". It means that alpha channel color is set to red.

Also we specify accuracy attr to be 0.7. Accuracy is the value between 0 and 1. It should be lower if you wish more shades of specified color be transparent and vice versa. By default accuracy="0.95".

Custom shader

There is a possibility to apply your own custom shader. Add shader attr:

<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:custom="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <com.alphamovie.lib.AlphaMovieView
        android:id="@+id/video_player"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        custom:shader="@string/shader_custom"/>
</FrameLayout>

And define your custom shader in string values, for example:

<resources>
    <!-- ... other string resources -->
    <string name="shader_custom">#extension GL_OES_EGL_image_external : require\n
            precision mediump float;
            varying vec2 vTextureCoord;
            uniform samplerExternalOES sTexture;
            varying mediump float text_alpha_out;
            void main() {
              vec4 color = texture2D(sTexture, vTextureCoord);
              if (color.g - color.r >= 0.1 &amp;&amp; color.g - color.b >= 0.1) {
                  gl_FragColor = vec4(color.r, (color.r + color.b) / 2.0, color.b, 1.0 - color.g);
              } else {
                  gl_FragColor = vec4(color.r, color.g, color.b, color.a);
              }
            }
    </string>
</resources>

In this case accuracy and alphaColor attrs are not affecting anything because they are used only when custom shader is not defined.


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