缩放(scale)我有一个疑问

```
RectF rect1 = new RectF(0,-200,200,0); // 矩形区域
Paint paint1= new Paint();
paint1.setColor(Color.BLACK);
Paint paint2= new Paint();
paint2.setColor(Color.BLUE);

canvas.drawRect(rect1,paint1);
canvas.scale(0.5f,0.5f,100,0);
//画一个缩放前 矩形蓝
canvas.drawRect(rect1,paint2);
```

```
RectF rect1 = new RectF(0,-200,200,0); // 矩形区域
Paint paint1= new Paint();
paint1.setColor(Color.BLACK);
Paint paint2= new Paint();
paint2.setColor(Color.BLUE);

canvas.drawRect(rect1,paint1);
canvas.scale(0.5f,0.5f,200,0);
//画一个缩放前 矩形蓝
canvas.drawRect(rect1,paint2);
```

我将蓝色矩形第一次移动100，缩放中心移动100，位于黑色矩形底部中心。
然而第二次移动200，缩放中心应该在黑色矩形右边线上，目测只是移动了50。
那么移动距离究竟从哪里测量才对？