title: Merge 2 image outputs (HDMI, DVI, VGA, or other) on one screen
body: <p>I am looking for something uncommon:
  A device that would allow to merge the image coming from 2 outputs (HDMI, DVI, VGA or any other type of image output) into one final image displayed onscreen.
  The outputs can be of the same type (e.g. 2 HDMIs) or different, anything that works would do. In case that isn't clear, here is a simple schema:</p>
  
  <p><a href="https://i.stack.imgur.com/SJ36M.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/SJ36M.png" alt="Image merging"></a></p>
  
  <p>It could work in different ways, for example with a system of priority (e.g. output 1 write its image and the output 2 overwrite non transparent pixels), less ideally by addition (e.g. if there is a red pixel 0xFF0000 on output 1 and a green pixel 0x00FF00 at the same position on output 2, the pixel becomes yellow 0xFFFF00), or any other method.</p>
  
  <p>I checked the available devices and none of them seem to be able to do this.
  Another solution would be to have a separate computer, able to capture video input from the outputs of the main computer, does the merging operation and send the image to the screen for display.
  The video capture device I could find only have one input and one output to record then display the image (these are generally game streaming devices) and wouldn't allow me to merge the images in real time.
  I could not find a video capture card for computer with multiple inputs that I could use to merge the images either.</p>
  
  <p>If you have any idea on how to accomplish this, please let me know.</p>
  
  <p>Thank you and have a good one.</p>