获取有关Canvas位图背景的触摸坐标

Question

我的目标是创建一个自定义视图，其中将位图设置为背景。用户可以在其上突出显示/绘制线条。我可以通过从View扩展一个类并重写onDraw方法来实现此目的。但是问题是如何获得相对于位图的触摸坐标？我想保存这些坐标并将其上传到云中，以便可以在其他设备上重画线。我不想将画布转换为位图，然后保存。 这是当前的代码，只画线-

public class HighlightView extends View {
    private Path drawPath;
    private Paint canvasPaint;
    private Paint drawPaint;
    private int paintColor = 0x660000;
    private Canvas drawCanvas;
    private Bitmap canvasBitmap;
    private float currentBrushSize;
    private ArrayList<Path> paths = new ArrayList<>();
    private float mX, mY;
    private static final float TOUCH_TOLERANCE = 4;

    private void init() {
        currentBrushSize = 50;

        drawPath = new Path();
        drawPaint = new Paint();
        drawPaint.setColor(paintColor);
        drawPaint.setAntiAlias(true);
        drawPaint.setStrokeWidth(currentBrushSize);
        drawPaint.setStyle(Paint.Style.STROKE);
        drawPaint.setStrokeJoin(Paint.Join.ROUND);
        drawPaint.setStrokeCap(Paint.Cap.ROUND);
        drawPaint.setAlpha(100);

        canvasPaint = new Paint(Paint.DITHER_FLAG);

    }


    public HighlightView(Context context, AttributeSet attrs) {
        super(context, attrs);
        init();
    }

    @Override
    protected void onDraw(Canvas canvas) {
        for (Path p : paths) {
            canvas.drawPath(p, drawPaint);
        }
        canvas.drawPath(drawPath, drawPaint);
    }

    @Override
    protected void onSizeChanged(int w, int h, int oldw, int oldh) {
        super.onSizeChanged(w, h, oldw, oldh);

        canvasBitmap = Bitmap.createBitmap(w, h, Bitmap.Config.ARGB_8888);

        drawCanvas = new Canvas(canvasBitmap);
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        float touchX = event.getX();
        float touchY = event.getY();

        switch (event.getAction()) {
            case MotionEvent.ACTION_DOWN:
                touch_start(touchX, touchY);
                invalidate();
                break;
            case MotionEvent.ACTION_MOVE:
                touch_move(touchX, touchY);
                invalidate();
                break;
            case MotionEvent.ACTION_UP:
                touch_up();
                invalidate();
                break;
            default:
                return false;
        }
        return true;
    }

    private void touch_start(float x, float y) {
        drawPath.reset();
        drawPath.moveTo(x, y);
        mX = x;
        mY = y;
    }

    private void touch_up() {
        drawPath.lineTo(mX, mY);
        drawCanvas.drawPath(drawPath, drawPaint);
        paths.add(drawPath);
        drawPath = new Path();

    }

    private void touch_move(float x, float y) {
        float dx = Math.abs(x - mX);
        float dy = Math.abs(y - mY);
        if (dx >= TOUCH_TOLERANCE || dy >= TOUCH_TOLERANCE) {
            drawPath.quadTo(mX, mY, (x + mX) / 2, (y + mY) / 2);
            mX = x;
            mY = y;
        }
    }

    public void onClickUndo() {
        if (paths.size() > 0) {
            paths.remove(paths.size() - 1);
            invalidate();
        }

    }

    public void onClickClearAll() {
        if (paths.size()>0){
            paths.clear();
            invalidate();
        }
    }
}