Hi! I know there are a lot of CAM out there for raster engraving.
I tried several of them but I didn't find one with at least the following features:
  • optimized path (skip blank segments or lines)
  • non-linear mapping of laser power (to linearize the resulting grayscale)
  • S0 when outside working frame

The last point is simple but important: most CAM allows you to set the minimum laser power (the "white" PWM output). Usually this is a non-zero value, because at a given speed the material won't burn so if it is zero you will lose the lightest gray shades. BUT when the tool moves outside the working frame to invert its direction the speed will drop to zero and if the laser power is not 0 it will engrave a dot!