After changing the measurement unit, do the following code need to be changed accordingly?

            var imageWidthPx = myImage.PixelWidth * 96 / myImage.DpiX;
var imageHeightPx = myImage.PixelHeight * 96 / myImage.DpiY;
var imageWidth = GraphicsUnit.Pixel.Convert(imageWidthPx, diagram.MeasureUnit);
var imageHeight = GraphicsUnit.Pixel.Convert(imageHeightPx, diagram.MeasureUnit);

Thanks a lot, Lyubo.

private void Window_Loaded(object sender, RoutedEventArgs e)
        {
            diagram.MeasureUnit = GraphicsUnit.Millimeter;
            ruler.Unit = RulerUnit.Millimeter;

        }

private void ImageManipulation(string path)
        {
            var myImage = new BitmapImage(new Uri(path));

            var imageWidthPx = myImage.PixelWidth * 96 / myImage.DpiX;
            var imageHeightPx = myImage.PixelHeight * 96 / myImage.DpiY;
            var imageWidth = GraphicsUnit.Pixel.Convert(imageWidthPx, diagram.MeasureUnit);
            var imageHeight = GraphicsUnit.Pixel.Convert(imageHeightPx, diagram.MeasureUnit);

            imageNode = diagram.Factory.CreateShapeNode(0, 0, imageWidth, imageHeight);
            imageNode.Image = myImage;
            imageNode.Shape = Shapes.Rectangle;
            imageNode.CustomDraw = CustomDraw.Additional;
            imageNode.ImageAlign = ImageAlign.Fit;

            var overlayNodeWidth = 200;
            var overlayNodeHeight = 200;

            overlayNode = diagram.Factory.CreateShapeNode(imageNode.Bounds.Right - overlayNodeWidth,
  imageNode.Bounds.Bottom - overlayNodeHeight, overlayNodeWidth, overlayNodeHeight);
            overlayNode.Shape = Shapes.Rectangle;
            overlayNode.Brush = Brushes.Transparent;
            overlayNode.Locked = true;
            overlayNode.AttachTo(imageNode, AttachToNode.BottomRight);
        }

I used the above code, but the length and width of the displayed imageNode differs from the actual length and width by about 35 mm. Does this code need to be adjusted: var imageWidthPx = myImage.PixelWidth * 96 / myImage.DpiX;
            var imageHeightPx = myImage.PixelHeight * 96 / myImage.DpiY;
            var imageWidth = GraphicsUnit.Pixel.Convert (imageWidthPx, diagram.MeasureUnit);
            var imageHeight = GraphicsUnit.Pixel.Convert (imageHeightPx, diagram.MeasureUnit);

Added:
This is the actual size.

Hey, Lyubo.
The picture size is shown in Figure 1: 2439X1322.
When I open the local image successfully, I call the ImageManipulation method. But the result is different from the actual one. I measured the real circuit board with a real tape measure and it is indeed a small value measured by our Diagram. Don't know where the problem is? What changes should be made？
I urgently need to resolve this issue to continue working.

Hey, Lyubo.
I have monitored the following variables step by step. I set the node size of imageNode at this location. There must be something wrong with this ImageManipulation (string path) method. Help me see what changes I need to make in this code.

Is something wrong here? because it involves two nodes.

private void ImageManipulation(string path)
        {
            var myImage = new BitmapImage(new Uri(path));

            var imageWidthPx = myImage.PixelWidth * 96 / myImage.DpiX;
            var imageHeightPx = myImage.PixelHeight * 96 / myImage.DpiY;
            var imageWidth = GraphicsUnit.Pixel.Convert(imageWidthPx, diagram.MeasureUnit);
            var imageHeight = GraphicsUnit.Pixel.Convert(imageHeightPx, diagram.MeasureUnit);

            imageNode = diagram.Factory.CreateShapeNode(0, 0, imageWidth, imageHeight);
            imageNode.Image = myImage;
            imageNode.Shape = Shapes.Rectangle;
            imageNode.CustomDraw = CustomDraw.Additional;
            imageNode.ImageAlign = ImageAlign.Fit;

            //overlayNode = diagram.Factory.CreateShapeNode(0, 0, 150, 150);
            var overlayNodeWidth = 50;
            var overlayNodeHeight = 50;

            overlayNode = diagram.Factory.CreateShapeNode(imageNode.Bounds.Right - overlayNodeWidth,
  imageNode.Bounds.Bottom - overlayNodeHeight, overlayNodeWidth, overlayNodeHeight);
            overlayNode.Shape = Shapes.Rectangle;
            overlayNode.Brush = Brushes.Transparent;
            //overlayNode.StrokeThickness = 0;
            overlayNode.Locked = true;
            overlayNode.AttachTo(imageNode, AttachToNode.BottomRight);
        }

private void diagram_DrawNode(object sender, DrawNodeEventArgs e)
{
if (e.Node != imageNode)
return;

var graphics = e.Graphics;
var clip = new CombinedGeometry(
GeometryCombineMode.Exclude,
new RectangleGeometry(imageNode.Bounds),
new RectangleGeometry(overlayNode.Bounds));
var translate = new TranslateTransform(-imageNode.Bounds.X, -imageNode.Bounds.Y);
graphics.PushTransform(translate);
graphics.PushClip(clip);
graphics.DrawRectangle(new SolidColorBrush(Color.FromArgb(120, 0, 0, 0)), null, imageNode.Bounds);
graphics.Pop();
graphics.Pop();
}

Both imageWidthPx and imageHeightPx are correct values. There are errors in the imageWidth and imageHeight converted from the GraphicsUnit.Pixel.Convert method, respectively. Then it proves that there is an error in the GraphicsUnit.Pixel.Convert method. Please tell me how to change it.