This is an imageview extension to create a masked imageview

MaskedImageView.java

import java.io.InputStream;
import java.net.URL;
import android.content.Context;
import android.content.res.Resources;
import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.PorterDuff;
import android.graphics.PorterDuffXfermode;
import android.graphics.Xfermode;
import android.graphics.drawable.BitmapDrawable;
import android.graphics.drawable.Drawable;
import android.util.AttributeSet;
import android.util.Log;
import android.util.TypedValue;
import android.widget.ImageView;

public class MaskedImageView extends ImageView {
  Bitmap resultBitmap = null;
  Paint paint = new Paint();
  Bitmap mOriginalBitmap;
  Context context;

  // I am using Mode.SRC_IN, you can choose your own mode by looking at demos that fits your needs
  private static final Xfermode sModes = new PorterDuffXfermode(PorterDuff.Mode.SRC_IN);

  //This is for creating image that have specified dp values, you do not have to do this
  int iW = getPixelValueFromDip(120);
  int iH = getPixelValueFromDip(70);

  // create a bitmap with a circle, used for the "dst" image

  private Bitmap makeDst() {
    //you can return your mask image here
    return RETURN_YOUR_MASK_BITMAP_HERE;
  }

  //get your source image that will be masked
  private Bitmap makeSrc()    {
    if (mOriginalBitmap == null) {
      Drawable drawable = getDrawable();
      Bitmap bitmap = ((BitmapDrawable) drawable).getBitmap();
      Bitmap mOriginalBitmap = bitmap;
      mOriginalBitmap = Bitmap.createScaledBitmap(mOriginalBitmap, iW, iH, true);
      return mOriginalBitmap;
    } else        {
      return mOriginalBitmap;
    }
  }

  //I use this class to convert correct pixel values from dp values, you do not have to use
  public int getPixelValueFromDip(int dpIntValue)    {
    float dpValue = Float.valueOf(dpIntValue);
    Resources r = getResources(); 
    float px = TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, dpValue, r.getDisplayMetrics());
    return Math.round(px);
  }

  //constructors here
  public MaskedImageView(Context context)    {
    this(context, null);
  }

  public MaskedImageView(Context context, AttributeSet attrs)    {
    super(context, attrs);
  }

  //onDraw method is important here, but remember that if you are animating image than onDraw will be called a lot, and these calculations can cause performance drop
  @Override
  protected void onDraw(Canvas canvas)    {
    //these width and height values are specific to my project, you can use anything you want
    int w = 200, h = 200;
    Bitmap.Config conf = Bitmap.Config.ARGB_8888; // see other conf types
    Bitmap bmp = Bitmap.createBitmap(w, h, conf); // this creates a MUTABLE bitmap
    canvas.drawColor(Color.TRANSPARENT);
    int x = 0;
    int y = 0;
    int sc = canvas.saveLayer(x, y, x + 200, y + 200, null, Canvas.MATRIX_SAVE_FLAG | Canvas.CLIP_SAVE_FLAG
        | Canvas.HAS_ALPHA_LAYER_SAVE_FLAG | Canvas.FULL_COLOR_LAYER_SAVE_FLAG
        | Canvas.CLIP_TO_LAYER_SAVE_FLAG);
    canvas.drawBitmap(makeDst(), 0, 0, paint);
    paint.setXfermode(sModes);
    canvas.drawBitmap(makeSrc(), 0, 0, paint);
    paint.setXfermode(null);
    canvas.restoreToCount(sc);
  }
}