How can I fire a key press or mouse click event without touching any input device at system level?

Question

How can I fire an automatic key press or mouse click event when a color appears on the screen on other application or browser?

Answer 1

It depends a lot on what you want. Do you want to send the keys to

• your Application
• another fixed Application
• Simulate a global keypress

Simulating keys globally

All of these will cause problems targeting a specific application and the active window changes.

• SendKeys Sends Messages to the active app. It's a high level function taking a string which encodes a sequence of keys.

• keybd_event is very low level and injects a global keypress. In most cases SendKeys is easier to use.

• mouse_event simulates mouse input.

• SendInput supersedes these functions. It's more flexible but a bit harder to use.

Sending to a specific window

When working with a fixed target window, sending it messages can work depending on how the window works. But since this doesn't update all states it might not always work. But you don't have a race condition with changing window focus, which is worth a lot.

• WM_CHAR sends a character in the basic multilingual plane (16 bit)
• WM_UNICHAR sends a character supporting the whole unicode range
• WM_KEYDOWN and WM_KEYUP Sends keys which will be translated to characters by the keyboard layout.

My recommendation is when targeting a specific window/application try using messages first, and only if that fails try one of the lower level solutions.

Answer 2

when a color appears on the screen on other application or browser

I made one program using OpenCV and C++ for operating mouse with finger gesture. I used 3 color strips for 3 mouse function.

• Yellow color for Left click
• Blue color for Right click
• Pink color for controlling cursor position

Whenever camera detect these colors, associated function takes place, I have used mouse_event for performing mouse function. For more information you may read my code, blog, video.