Get the Bitmap:

Bitmap bitmap = getthebitmapyouwanttoshowinacirclefromsomewhere;
Bitmap circleBitmap = Bitmap.createBitmap(bitmap.getWidth(), bitmap.getHeight(), Bitmap.Config.ARGB_8888);

Use a shader:

BitmapShader shader = new BitmapShader (bitmap,  TileMode.CLAMP, TileMode.CLAMP);
Paint paint = new Paint();
        paint.setShader(shader);

Draw the canvas;

Canvas c = new Canvas(circleBitmap);
c.drawCircle(bitmap.getWidth()/2, bitmap.getHeight()/2, bitmap.getWidth()/2, paint);

Set the image:

myImageView.setImageBitmap(circleBitmap);