I found a site full of examples to create knots in latex and it's quite a pain to paint them. They look nice, though. You basically paint them via xy and then place *"holes"* in the parts where you want to make a crossing. Here is an example:
\xy
 (-3.5,3.5)*{}="LEFTTOP";
 (3.5,-3.5)*{}="RIGHTBOTTOM";
 (3.5,3.5)*{}="RIGHTTOP";
 (-3.5,-3.5)*{}="LEFTBOTTOM";
 "LEFTTOP";"RIGHTBOTTOM" **\dir{-}; \POS?(.5)*{\hole}="HOLE";
 "RIGHTTOP";"HOLE" **\dir{-};
 "HOLE";"LEFTBOTTOM" **\dir{-};
 (0,0)*[gray]\xycircle(5,5){-};
\endxy


Everyone who tried to get isolate compiled tex-code in an svg knows that this is kind of complicated if you try to do it by hand and via manual picture editing. So it sounds convenient that there exists a software that inputs Tex-Code in a software like Inscape ... and so it is! After running into a lot of 32 / 64 bit problems and some weird dll-issues when I had ImageMagick or GraphicsMagick installed I finally got the following to work (assuming that you have Miktex installed): * Inkscape 0.46 (not motivated to install it in the current version and it now runs though) * Download and Install pstoedit (be sure to install it without this Magick-Integration and put the folder of the executable in your path). * Download and Install textext. For those who are interested (i.e. myself, when I try to set it up on someone else's computer), here are the details. For faster debugging I used and edited the textext.py-File in the Inkscape Extension Folder:
Func SendF($str)
$clip = ClipGet()
ClipPut($str)
Send("^v")
ClipPut($clip)
EndFunc

Run('PATHTO046\inkscape.exe')
WinWaitActive('New document')
Send('^o')
WinWaitActive('Select file')
SendF('PATHTO\test.svg')
Send('{ENTER}')
WinWaitActive('test.svg')
Send('!c{DOWN 8}{ENTER}')
WinWaitActive('TeX Text')
SendF('$\alpha\leq\beta$')
Send('!o')
to finally get that it calls something like
pstoedit -f plot-svg tmp.pdf test.svg -dt -ssp -psarg -r9600x9600
which results in the errors I then tracked down to the problems with CORE_RL_Magick++_.dll. Links that helped me: * http://www.calcmaster.net/personal_projects/pdf2svg/ * http://pav.iki.fi/software/textext/ * http://www.pstoedit.net/