Screenshot WPF app not working on second monitor - wpf

Question

There are other similar questions, but they deal with only screenshotting the displayed application. My application is transparent, so I need to take a screenshot of both the displayed window and the background behind it.
This function correctly screenshots the app on my main monitor, but when it goes to the other monitor, the screenshots are the wrong shape and are completely black. If the window is partly on the monitor, then it still works, but as soon as the other monitor takes control of the window, I get black screenshots. How do I get the screenshots to render correctly?
Here is my function:
public void SaveSnapshot2(int count)
{
string imageName = "image" + count.ToString() + ".jpeg";
string basePath = Path.GetFullPath(Environment.CurrentDirectory);
string folderPath = Path.Combine(basePath, "Snapshots");
string fullPath = Path.Combine(folderPath, imageName);
if (!Directory.Exists(folderPath))
{
Directory.CreateDirectory(folderPath);
}
System.Windows.Point relativeWindowPosition = App.Current.MainWindow.PointToScreen(new System.Windows.Point(0, 0));
System.Windows.Point relativeBottomRightWindowPosition = App.Current.MainWindow.PointToScreen(new System.Windows.Point(App.Current.MainWindow.Width, App.Current.MainWindow.Height));
System.Windows.Point actualWidthHeight = new System.Windows.Point((relativeBottomRightWindowPosition.X - relativeWindowPosition.X), (relativeBottomRightWindowPosition.Y - relativeWindowPosition.Y));
System.Drawing.Size convertedSize = new System.Drawing.Size((int)actualWidthHeight.X, (int)actualWidthHeight.Y);
Bitmap Screenshot = new Bitmap((int)actualWidthHeight.X, (int)actualWidthHeight.Y, PixelFormat.Format32bppArgb);
using (Graphics g = Graphics.FromImage(Screenshot))
{
// Crops the screenshot
// The relativePoint is where the top left corner of the image is. This is correct.
g.CopyFromScreen((int)relativeWindowPosition.X, (int)relativeWindowPosition.Y, 0, 0, convertedSize); // or (0, 0, 0, 0, Screenshot.Size) to get the whole bitmap image
}
try
{
Screenshot.Save(fullPath, ImageFormat.Jpeg);
}
catch (Exception ex)
{
MessageBox.Show(ex.Message + ", the image did not save.");
}
Screenshot.Dispose();
}
Coming up with names for the points was difficult. I hope they are clear enough.
Does the coordinate system change when a window is on a separate monitor? Am I going about this the right way?

Answer 1

I guess you have not declared DPI awareness in the application manifest. It's a common pitfall when you have multiple monitors of different DPI. If have not, most methods and functions related to screen coordinates will return incorrect values and thus the calculation based on those values will be screwed up.
To solve this, add the application manifest which declares DPI awareness. See Setting the default DPI awareness for a process. PerMonitorV2 is the key for Per-Monitor DPI.