Zoom out در CanvasView (حل شد)

سلام

من یه CanvasView  دارم که برای رسم چند نمودار هست و برای بهتر دیده شدن نمودارها zoom و scroll هم میشه انجام داد . مشکل اینجاست که وقتی zoom out می کنم میخوام تصویر align center بشه اما نمی دونم چطوری! کسی از دوستان میتونه راهنماییم کنه ؟

کد CanvasView منهای قسمتهای ترسیم خط و خطوط  اینه : 

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.util.AttributeSet;
import android.view.GestureDetector;
import android.view.MotionEvent;
import android.view.ScaleGestureDetector;
import android.widget.ImageView;

class CanvasBar extends ImageView {

private ScaleGestureDetector mScaleDetector;
private float mScaleFactor = 1.f;
private GestureDetector mGestureDetector;
private float mBoardScale = 2f;
private float mBoardScrollX = 0f;
private float mBoardScrollY = 0f;

public CanvasBar(Context context, AttributeSet attrs, int defStyleAttr) {
  super(context, attrs, defStyleAttr);
  initilize();
  mScaleDetector = new ScaleGestureDetector(context, new ScaleListener());
  mGestureDetector = new GestureDetector(context, new GestureListener());
}

public CanvasBar(Context context, AttributeSet attrs) {
  super(context, attrs);
  initilize();
  mScaleDetector = new ScaleGestureDetector(context, new ScaleListener());
  mGestureDetector = new GestureDetector(context, new GestureListener());
}

public CanvasBar(Context context) {
  super(context);
  initilize();
  mScaleDetector = new ScaleGestureDetector(context, new ScaleListener());
  mGestureDetector = new GestureDetector(context, new GestureListener());
}

public void initilize(){
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}

@Override
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
  super.onSizeChanged(w,h,oldw,oldh);
  height = getHeight();
  width = getWidth();
  mBoardScale = Math.max(w / width, h / height);

  float minScrollX = w - mBoardScale * width;
  float minScrollY = h - mBoardScale * height;

  mBoardScrollX = minScrollX / 2;
  mBoardScrollY = minScrollY / 2;
}

@Override
public boolean onTouchEvent(MotionEvent ev) {
  mScaleDetector.onTouchEvent(ev);
  mGestureDetector.onTouchEvent(ev);

  return true;
}


@Override
protected void onDraw(Canvas canvas) {
  super.onDraw(canvas);

  canvas.save();
  canvas.scale(mScaleFactor, mScaleFactor);
  canvas.translate(mBoardScrollX / mBoardScale, mBoardScrollY / mBoardScale);
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    canvas.restore();
  }
  private class ScaleListener extends ScaleGestureDetector.SimpleOnScaleGestureListener {
    @Override
    public boolean onScale(ScaleGestureDetector detector) {
      mScaleFactor *= detector.getScaleFactor();
      mScaleFactor = Math.max(1.0f, Math.min(mScaleFactor, 5.0f));
      postInvalidate();
      return true;
    }
  }

  private  class  GestureListener extends GestureDetector.SimpleOnGestureListener {
    @Override
    public boolean onScroll(MotionEvent e1, MotionEvent e2, float dX, float dY) {
      mBoardScrollX -= dX;
      mBoardScrollY -= dY;
      postInvalidate();
      return true;
    }
  }
}