Hi. When I open a 1bit indexed gimp png file. When exporting it to send it to the home plotter in raster mode, if I change the dpi or size, it converts the image to grayscale. 

Why does the color matter for your plotter? (serious question, this might still be a bug)

My ploter is a cnc laser(On / Off mode). When I print a photo, the best result is in 1 color. Because inkscape softens the image, which makes you have to search, from what color to activate the laser. Result is very light or dark images. Thank you.

I see. I wonder if you could import the image in the exact size that you need?

Yes, I have no problem, but it was to know, and improve. I am developing my cnc software and my inkscape extensions. 

Ah, I see, thanks. The forum isn't the ideal place for bug reports, though. Could you post the bug description at https://inkscape.org/report , please?