PyTartan

Convert tartan threadcount specification to SVG

Tartans (Scottish plaids) are  specified in terms of a "threadcount", which
indicate the colors of the stripes and their order and thickness.  See
http://en.wikipedia.org/wiki/Tartan#Construction and/or
http://www.tartanregister.gov.uk/guidance.html#20 for some information.

Usage:  tartan.py [-a] [-u unit] [-r reps] [-d divisor] [-R] [sett info...]

Options:
	-a:	Sett is asymmetrical.  The pattern is simply repeated over
	and over, not reflected about the pivots as usual.

	-u: 	Make the width of the slantwise stripes representing the
        threads equal to _unit_.  Larger numbers (like 5-10) will result
        in larger images with more "hound's-tooth" look to them.  Not
        really necessary since SVGs are scalable.  Default: 2

	-r:    	Repeat the pattern _reps_ times horizontally and
        vertically.  Default: 2

	-d:	Divide all the widths by _divisor_, e.g. since threadcounts
        are supposed to be all even numbers, many are given essentially
        multiplied by two.  Also not all that necessary since SVGs are
        scalable.  Default: 1

	-R:	*Ignore* the threadcount on the command line, and instead
        read in standard input.  The input is taken to be of the form that
        www.tartanregister.gov.uk sends back in email when you request a
        threadcount.  The program will find the "Threadcount:" line for the
        actual threadcount, and will parse the "Pallett:" line for
        assigning the precise RBG colors to the thread colors.  All the
        rest of the input is ignored.

The threadcount is expected to consist of one or more specifiers of color
and width.  Color is usually indicated by one or two letters (sometimes
more), and then comes the width in numbers.  So W6 means a white stripe six
threads wide, and B18 means a blue stripe 18 threads wide.  There may be
spaces between the strips, but there should not be whitespace between a
color and its number.  Standard color-abbreviations are understood, among
them:
	W:	White
	K:	Black
	R:	Red
	G:	Green
	B:	Blue
	Y:	Yellow
	N:	Grey
	T:	Tan
	DB:	Dark Blue
	LG:	Light Green

You can also specify the color precisely by using the form (#rrggbb) as
the color.  The parentheses are mandatory, as is the pound sign, and the
six hex digits after represent, in pairs, the red, green, and blue
components of the color.  As usual, there must be no space between the
closing paren and the count number.  The official Tartan Registry
accompanies each threadcount with a pallette which specifies the shade (in
#rrggbb form) for each color abbreviation used; these are processed by the
program using the (#rrggbb) form for the colors, internally.

Threadcounts are usually symmetrical.  That is, reading across (for
example), you should find stripe#1, stripe#2, ... , stripe#(n-1), stripe#n,
which would then be followed by stripe#(n-1), stripe#(n-2),...,stripe#2,
stripe#1, stripe#2, stripe#3, etc.  That is, the sequence is reversed for
each repeat.  Note that the end ("pivot") stripes are not generally
repeated.  If you use the -a option, the threadcount is used
asymmetrically, repeating from stripe#1 to stripe#n over and over with no
reversals.  Asymmetrical tartans exist in the Tartan Registry, but as yet I
have not seen that they indicate them at all in the threadcounts they send
back.

To have different counts for warp vs weft, separate them with the '|'
character (which will have to be escaped from the shell!), e.g.

tartan.py -r 4 'B20 W30 | W30 R16' 

Acknowledgement: Inspiration for this program was from xtartan by Jim
McBeath, as modified by Joseph Shelby.