Question

I’am using PictureBox for displaying images. My images are direct from scanner so the resolutions are up to 4000*4000… Because my display area is a lot smaller I have to display the image with pictureBox1.SizeMode = PictureBoxSizeMode.Zoom; to preserve aspect ratio.
After that the image is in the middle of the screen.

How can I find the distance between the left side of the image control and the REAL left side of an actual image (see image bellow).

Is there any solution?

Btw. displaying the image on the left side of the screen would do the trick too.

        var imageHeight = pictureBox1.Image.Height;
        var imageWidth = pictureBox1.Image.Width;
        var userSelection = rect.Rect;

        var display = pictureBox1.DisplayRectangle;
        var xFactor = (float)userSelection.Width / display.Width;
        var yFactor = (float)userSelection.Height / display.Height;

        var realCropSizeWidth = xFactor * imageWidth;
        var realCropSizeHight = yFactor * imageHeight;

        var realCropX = imageWidth / display.Width;
        realCropX *= userSelection.X;
        var realCropY = imageHeight / display.Height;
        realCropY *= userSelection.Y;

        var realCropRectangle = new Rectangle(realCropX, realCropY, (int)realCropSizeWidth,
                                              (int)realCropSizeHight);

        var image = CropImage(pictureBox1.Image, realCropRectangle);
        pictureBox1.Image = image;

        public Image CropImage(Image source, Rectangle rectangle)
    {
        var target = new Bitmap(rectangle.Width, rectangle.Height);
        using (var g = Graphics.FromImage(target))
        {
            g.DrawImage(source, new Rectangle(0, 0, target.Width, target.Height),
                             rectangle,
                             GraphicsUnit.Pixel);
        }
        return target;
    }

Answer 1

As far as I know there is no direct way of getting what you want, but some simple maths would suffice:

You know the aspect ratio of your original image which is preserved and you know the aspect ratio of your picturebox in which you are showing it. Based on that you can figure out which dimension (height or width) the image fits exactly. Once you know that you can obtain the scaling factor of the image and therefore you can calculate the other dimension of the shown image.

As the image will be centered on the dimension that is not fitted exactly to the picturebox, its straighforward to get the distance you are looking for.