Usage:
- label= parameter adds text on a transparent background at point x1,y1, using text-color, text-size, text-angle, label-pos=left/right/top/bottom.
- shape=circle, square, diamond are equel width centered on x1,y1, and use mark-size.
- line (2 'ends') rule (rotate around single centre) curveA, curveC, ruleA (with an arrowhead)
- box and ellipse allow mark-size=w,h to set width and height. A third number for box sets corner-radius.
- shape=panel has its top-left corner at x1,y1, places text within rather than beside the shape, and uses mark-size, border-radius, shape-angle.
- shape=image, uses the value in 'mark' or default red pog. Set mark-size. Height may be needed to align labels correctly, but doesn't affect the image itself.
- A 'photo-panel' option creates a 'standard' 50px high panel, adds a photo to left or right. A width dimension is needed to match the panel edge)
- All shapes can also set shape-color and optional opacity, and a shape-outline parameter to set line-width, color and opacity.
- Shapes can also be set to auto- or manual-numbers to give a sequence of numbered shapes.
- Labels can optionally have a line to connect to their shape, as can shape-numbers if the shapes are congested.
- label-size can optionally include a plain background and/or 1px black outline around the label. eg label-size=12,outline,background