wpf 标尺 刻度尺 适用于图像缩放

xaml部分主要代码：

<Canvas x:Name="cvRuler" Margin="0" Background="WhiteSmoke" TextBlock.Foreground="Black"/>

后台主要代码

        //画标尺
        private void DrawRule()
        {

            if (cvRuler.Children != null)
            {
                cvRuler.Children.Clear();
            }

            System.Windows.Shapes.Line _line;
            TextBlock _textBlock;
            
            var xScale =你的缩放倍数;

            int _lineIndex = 0;
            double _width = cvRuler.ActualWidth;//展示部分总pixel
            string _unit = "(cm)";
            float _inch = (float)5195/600;//dpi为600时，对应总英寸
            float _cm = (float)(_inch*2.54);//英寸换算成cm
            double _pixelPerline = _width/_cm/10*xScale;//刻度尺每cm对应多少pixel。分成十份，再乘以缩放倍数
            for (double i = 0; i < _width; i += _pixelPerline)
            {
                _line = new System.Windows.Shapes.Line();
                _line.X1 = i;
                _line.X2 = i;
                _line.Y1 = 0;
                _line.StrokeThickness = 1;
                if (_lineIndex % 10 == 0)//十份，最长的刻度线
                {
                    _line.Stroke = Brushes.DimGray;
                    _line.Y2 = 25;

                    _textBlock = new TextBlock();
                    _textBlock.Text = (_lineIndex/10).ToString()+(_lineIndex==0 ? _unit : "");
                    _textBlock.FontSize = 8;
                    _textBlock.HorizontalAlignment = HorizontalAlignment.Left;
                    _textBlock.VerticalAlignment = VerticalAlignment.Top;
                    _textBlock.Margin = new Thickness(i+2, 20, 0, 0);
                    cvRuler.Children.Add(_textBlock);
                }
                else if (_lineIndex % 5 == 0)//中间的刻度线
                {
                    _line.Stroke = Brushes.Gray;
                    _line.Y2 = 20;
                }
                else
                {
                    _line.Stroke = Brushes.Gray;
                    _line.Y2 = 15;
                }
                cvRuler.Children.Add(_line);

                _lineIndex++;
            }
        }