As it scans your raster, it will attempt to modulate the power. Lightburn can scale the power of the laser according to the brightness or darkness of each pixel.Remember there are not colors in laser cutting, the laser only cuts in one color (burnt). Lightburn will accept a full-color image, but will process it as gray scale.LightBurn can be used to etch raster images (jpg, png, bmp, etc) with some caveats: 123d Make can generate slices from 3D models that can be assembled into 3D objects (N cost, but not open source and no Linux support).GIMP can be used to create etch designs only.

It's like the 100% free and open source cousin of Adobe Photoshop.

GNU Image Manipulation Program (GIMP) is photo-editing software for creating or modifying raster images (jpg, png, bmp, etc).

Inkscape can be used to create designs that can include both etches and cuts in a single file. It's like the 100% free and open source cousin of Adobe Illustrator.

Inkscape is illustration software for creating or modifying vector images.

The Lightburn software is great for interfacing to the laser cutter and has basic drawing tools, but you are generally better of doing your designs in dedicated design software.

Inkscape to dxf