如何使得canvas里的图片能够进行旋转，而不导致整个画布的旋转

自定义的布局中，在一个Canvas里绘画了很多图片。现在想使得画布里的
每个图片都进行旋转。我使用了下面的代码

{
mRotation += 10;
if (mRotation > 360)
{

mRotation = mRotation % 360;

}
synchronized (lockObject)
{

for (int i = 0; i < particleList.size();i++)
{
    Picture particle = pictureList.get(i);
    Paint paint=new Paint();

    ......

    paint.setAlpha(particle.getAlpha());

   //rotate the bitmap
    canvas.save();
    Matrix matrix = new Matrix();
    matrix.postRotate(mRotation,particle
            .getPositionX() + particle.getParticleWidth()/2, particle.getPositionY() +
            particle.getParticleHeight()/2);
    canvas.drawBitmap(particle.getParticleImage(), matrix, paint);
    canvas.restore();
}

}

}