Only rectangular Cartesian grids are provided. You can choose the color of the grid lines, and the spacing and offsets from the image origin, independently for horizontal and vertical grid lines. You have a choice of five grid styles:
Appeareance
This style, the least obtrusive, shows a simple dot at each intersection of grid lines.
This style, the default, shows a plus-shaped crosshair at each intersection of grid lines.
This style shows dashed lines in the designated foreground color. It probably won't look good if the grid line spacing is small.
This style shows dashed lines alternating the designated foreground and background colors.
This style shows solid grid lines in the designated foreground color.
Click on on the color dwell to select a new color for the grid.
Spacing
You can fix cell size of the grid and select the unit of measurement.
Offset
You can fix the offset of the first cell. Coordinate origin is the upper left corner of the image. Coordinates start at (0,0).