android：为什么我无法旋转antiClockwise？

Question

在我的应用程序中，我应该像时钟指针一样顺时针和逆时针旋转底部中心。

我使用此代码：

private ImageView myImageView;
private float curScale = 1F;
private float curRotate = 70;
private Bitmap bitmap;
private int bmpHeight;

/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);
    myImageView = (ImageView) findViewById(R.id.imageview);

    bitmap = BitmapFactory.decodeResource(getResources(), R.drawable.teste);//here you insert your image
    bmpHeight = bitmap.getHeight();
    drawMatrix();

} 
    private void drawMatrix() {
    Matrix matrix = new Matrix();
    Matrix matrixb = new Matrix();
    Matrix matrixc = new Matrix();
    matrix.postScale(curScale, curScale);
    matrixb.setRotate(curRotate, 100, bmpHeight);
    matrixc.setTranslate(100, 0);
    matrix.setConcat(matrixb, matrixc);
    Bitmap targetBitmap = Bitmap.createBitmap(200, bmpHeight,
            bitmap.getConfig());
    Canvas canvas = new Canvas(targetBitmap);
    canvas.drawBitmap(bitmap, matrix, new Paint());
    myImageView.setImageBitmap(targetBitmap);
}

但我无法逆时针旋转它，因为图片的宽度会发生变化。 有什么办法吗？ 在此先感谢。