Android : drawing on canvas after get image from user

I want to show the image that taken by user gallery to a canvas to edit it after.but till now i can get image from user.but i dont know how to show the image by canvas this is my code :

public class second extends ActionBarActivity {

    private static int RESULT_LOAD_IMAGE = 1;
    Bitmap base;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Intent i = new Intent(
                Intent.ACTION_PICK,
                android.provider.MediaStore.Images.Media.EXTERNAL_CONTENT_URI);

        startActivityForResult(i, RESULT_LOAD_IMAGE);
    }
    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        super.onActivityResult(requestCode, resultCode, data);

        if (requestCode == RESULT_LOAD_IMAGE && resultCode == RESULT_OK && null != data) {
            Uri selectedImage = data.getData();
            String[] filePathColumn = { MediaStore.Images.Media.DATA };

            Cursor cursor = getContentResolver().query(selectedImage,
                    filePathColumn, null, null, null);
            cursor.moveToFirst();

            int columnIndex = cursor.getColumnIndex(filePathColumn[0]);
            String picturePath = cursor.getString(columnIndex);
            cursor.close();


            ImageView imageView = (ImageView) findViewById(R.id.imgView);
            imageView.setImageBitmap(BitmapFactory.decodeFile(picturePath));
        }
    }
}

i know to creat a canvas with Canvas canvas= new Canvas(image) and draw the bitmap by ondraw method. but still i dont figure out how to convert the photo that given from users gallery to canvas and show it