Using INKSCAPE for Linux (version 0.39, Inkscape.org)
*****************************************************
Marcus R Garvie
Jan 19, 2006


Here are some simple instructions for creating polygons, with nodes at the corners, and possibly 
along the straight line arcs too. The reason I used INKSCAPE instead of GIMP or some other graphics
package is that once the figure is complete it allows me to extract the coordinates of the nodes,
which can then be exported to some triangulation package, like DISTMESH.

Start-up
********
* In a command window type 'inkscape'

* Drag window to an appropriate size, and right/middle click (depending on mouse) several times
  to enlarge figure (or use menu)

Create a polygon with nodes at the corners
******************************************
* Click on 'Draw Bezier curves and straight lines (shift + F6)' (default is straight lines)

* To create a straight line segment, click the left mouse button and move mouse. Make last node
  coincide with first to close the polygon.

* To delete figure, click on 'Select and transform objects (F1)', left-click and hold to select
  a square around the whole figure. Press 'Delete' on the key-board.

 
Edit paths
**********
* Click on 'Edit path nodes or control handles (F2)', then click on figure to view nodes. 

* Can select individual nodes (become blue), or click and drag them. Can select more than 1
  node by holding down the shift key while clicking on the nodes. To select all the nodes hold the
  left mouse button down and drag a 'square' round the figure.

* To add more nodes between corners first select whole figure as above. Then repeatedly 
  click on the 'Insert new nodes ...' option on the temporary menu bar above (look for '+' sign). 
  Notice that nodes along any straight line segment are equally spaced, and that short segments
  will have nodes more densely packed than long segments. Can remedy this by deleting individual
  nodes.

Joining figures to make a single path
*************************************
* To keep things simple, suppose we wish to join a circle to a square. First create the circle 
  using the 'Create circle, ellipses, and arcs (F5)' button, and an overlapping rectangle using
  the 'Create rectangles and squares (F4)' button. Notice how they are by default filled with 
  colour. 

* To remove colour select the individual figures, from the 'Object' menu click on 'Fill and 
  stroke ...', then click on 'x' within the pop-up box. 

* To join the 2 figures, select the combined figure (as described above using F1), and from the 
  'Path' menu select 'Union'. At this stage we may wish to add more nodes along curved parts of the 
  figure (see 'Edit paths' above.)

* To convert curved arcs to straight line segments, click on 'Edit path nodes or control handles
  (F2)', select whole figure, and then click on the temporary menu button 'Make selected segments
  lines' (button has 2 nodes joined by a straight line segment).


Exporting the coordinates of nodes in a path
********************************************
* Click on 'Edit path nodes or control handles (F2)', click on figure so nodes visible, and then 
  click on the menu button that looks like '<x>' (XML Editor). 

* In the pop-up window click on the first 'attrubute' (begins with a 'd'). The node coordinates 
  will appear below on one line, separated by the letter 'L' (except at start and end, where there
  is an 'M' and then a 'z'.

* Copy the whole line of coordinates with letters to a text editor, and manually edit it so that
  it looks like

  34.888  899.443
  18.449  143.677
  ...     ...

  If anyone finds out how to do this automatically, please let me know! If this is to be imported
  into Matlab as an array, it will have to be edited a bit more. 


Problems with islands
*********************
* For the triangulation program we may need the coordinates for the perimeter of our domain to be in a
  separate file to the one with the coordinates of an 'island'. Create separate Inkscape figures for the
  island and the perimeter (just e.g., select and delete the nodes of the island to leave the perimeter)
  and save as a .png bitmap. Then proceed as described in 'Exporting the coordinates of nodes in a path'
  above for each figure.