recapture
Recapture is a Linux tool for capturing a section of a display and upscaling it on a different display, filling the entire screen. The mouse can also optionally be emulated.
Performance
This tool is is very CPU intensive. Increasing the capture area and upscale quality will decrease frame rate very quickly.
Also, I noticed that performance decreased significantly when compiling with Java 8 compared to Java 7, so I recommend using Java 7.
Configuration
The settings from the each session are saved in ~/.recapture/prefs.txt. The source and destination options represent the bounds of the source and destination displays respectively, and are stored in the format x,y,width,height.