In CorelDRAW, select the bitmap graphic, and from the menu, select Bitmap>Modes>Grayscale.
To laser properly, you need good contrast between each of the grayscale colors, especially those that are next to each other. The more original shades of color the graphic has, the more likely you will have conflicting shades next to one another. A graphic with many darker shades of colors such as reds and blues when converted to grayscale will have similar shades of gray. Yellows, pinks, and light greens and blues will have lighter shades of gray. If dark colors are next to light shades, your project will typically result in a successful lasering. Having several objects that are black and several that are white is ideal as they have the highest contrast.
—Bob Hagel, Eagle’s Mark