Writing code to take a screenshot

What does it take on Windows to take a screenshot and save it as an image file

Questions: which development environment and language?

Options:

• regular .NET. Pros: familiarity, lots of documentation
• .NET core. Pros: future proof. learn something new
• Python. Not sure if even possible, but enables workflow into AI

Development enviornment:

• Visual Studio Code. Lightweight. Future proof. Learning curve
• Full blown Visual Studio. Familiar

Data points:

• [.net core supported with VS code] on official MS documentation (https://docs.microsoft.com/en-us/dotnet/core/tutorials/with-visual-studio-code)

Decision: use .dot net Core with Visual Studio Code.

Setting up the development environment

• Official instructions on docs
• Started using .Net Core 3.1.202

Create git repo

Location on Git: https://github.com/haslhofer/screencapture

Create Hello World .Net Core app

Instructions: https://docs.microsoft.com/en-us/dotnet/core/tutorials/with-visual-studio-code

Find the right APIs for Screen capture in Windows

Option 1: PrintWindow

• example on stackoverflow

• using GDI –> solution chosen

add package to dot net core:

dotnet add package System.Drawing.Common

Issues along the way:

• Monitor scaling. Fix:

  call User32.SetProcessDPIAware();

• Multiple monitors: Article that describes doing this in C++ here
  • MonitorInfoEx structure

Capturing mouse and keyboard events Article to hook input:

• http://joelabrahamsson.com/detecting-mouse-and-keyboard-input-with-net/
• https://stackoverflow.com/questions/7497024/how-to-detect-mouse-clicks

Need to understand Windows GDI better:

• GDI introduction Virtual screen: The bounding rectangle of all the monitors is the virtual screen source
  • Each physical display is represented by a monitor handle of type HMONITOR.
  • Any function that returns a display device context (DC) normally returns a DC for the primary monitor
  • To obtain the DC for another monitor, use the EnumDisplayMonitors function
  • Or, you can use the device name from the GetMonitorInfo function to create a DC with CreateDC.