diagram-generator: Asymptote graphics

Author: jkseppan

diagram-generator/diagram-generator.lua

@@ -56,6 +56,10 @@ local dot_path = os.getenv("DOT") or "dot"
 -- document, use the meta data to define the key "pdflatex_path".
 local pdflatex_path = os.getenv("PDFLATEX") or "pdflatex"
 
+-- The asymptote path. There is also the metadata variable
+-- "asymptote_path".
+local asymptote_path = os.getenv ("ASYMPTOTE") or "asy"
+
 -- The default format is SVG i.e. vector graphics:
 local filetype = "svg"
 local mimetype = "image/svg+xml"
@@ -100,6 +104,9 @@ function Meta(meta)
   pdflatex_path = stringify(
     meta.pdflatex_path or meta.pdflatexPath or pdflatex_path
   )
+  asymptote_path = stringify(
+     meta.asymptote_path or meta.asymptotePath or asymptote_path
+  )
 end
 
 -- Call plantuml.jar with some parameters (cf. PlantUML help):
@@ -135,11 +142,10 @@ local tikz_template = [[
 \end{document}
 ]]
 
---- Returns a function which takes the filename of a PDF and a
--- target filename, and writes the input as the given format.
--- Returns `nil` if conversion into the target format is not
--- possible.
-local function convert_from_pdf(filetype)
+-- Returns a function which takes the filename of a PDF or SVG file
+-- and a target filename, and writes the input as the given format.
+-- Returns `nil` if conversion into the target format is not possible.
+local function convert_with_inkscape(filetype)
   -- Build the basic Inkscape command for the conversion
   local inkscape_output_args
   if filetype == 'png' then
@@ -165,7 +171,7 @@ end
 
 --- Compile LaTeX with Tikz code to an image
 local function tikz2image(src, filetype, additional_packages)
-  local convert = convert_from_pdf(filetype)
+  local convert = convert_with_inkscape(filetype)
   -- Bail if there is now known way from PDF to the target format.
   if not convert then
     error(string.format("Don't know how to convert pdf to %s.", filetype))
@@ -248,6 +254,50 @@ local function py2image(code, filetype)
     return imgData
 end
 
+--
+-- Asymptote
+--
+
+local function asymptote(code, filetype)
+  local convert
+  if filetype ~= 'svg' and filetype ~= 'png' then
+    error(string.format("Conversion to %s not implemented", filetype))
+  end
+  return with_temporary_directory(
+    "asymptote",
+    function(tmpdir)
+      return with_working_directory(
+        tmpdir,
+        function ()
+          local asy_file = "pandoc_diagram.asy"
+          local svg_file = "pandoc_diagram.svg"
+          local f = io.open(asy_file, 'w')
+          f:write(code)
+          f:close()
+
+          pandoc.pipe(asymptote_path, {"-f", "svg", "-o", "pandoc_diagram", asy_file}, "")
+
+          local r
+          if filetype == 'svg' then
+            r = io.open(svg_file, 'rb')
+          else
+            local png_file = "pandoc_diagram.png"
+            convert_with_inkscape("png")(svg_file, png_file)
+            r = io.open(png_file, 'rb')
+          end
+
+          local img_data
+          if r then
+            img_data = r:read("*all")
+            r:close()
+          else
+            error("could not read asymptote result file")
+          end
+          return img_data
+      end)
+  end)
+end
+
 -- Executes each document's code block to find matching code blocks:
 function CodeBlock(block)
 
@@ -260,6 +310,7 @@ function CodeBlock(block)
         graphviz = graphviz,
         tikz = tikz2image,
         py2image = py2image,
+        asymptote = asymptote,
     }
 
     -- Check if a converter exists for this block. If not, return the block

diagram-generator/sample.md

@@ -2,9 +2,9 @@
 
 ## Introduction
 This Lua filter is used to create images with or without captions from code
-blocks. Currently PlantUML, Graphviz, Ti*k*Z and Python can be processed.
-This document also serves as a test document, which is why the subsequent
-test diagrams are integrated in every supported language.
+blocks. Currently PlantUML, Graphviz, Ti*k*Z, Asymptote, and Python can be
+processed. This document also serves as a test document, which is why the
+subsequent test diagrams are integrated in every supported language.
 
 ## Prerequisites
 To be able to use this Lua filter, the respective external tools must be
@@ -211,6 +211,66 @@ key `activate_python_path` to `c:\ProgramData\Anaconda3\Scripts\activate.bat`.
 
 Pandoc will activate this Python environment and starts Python with your code.
 
+## Asymptote
+[Asymptote](https://asymptote.sourceforge.io/) is a graphics
+language inspired by Metapost. To use Asymptote, you will need to
+install the software itself, a TeX distribution such as
+[TeX Live](https://www.tug.org/texlive/), and
+[dvisvgm](https://dvisvgm.de/), which may be included in the TeX
+distribution.
+
+If png output is required (such as for the `docx`, `pptx` and `rtf`
+output formats) Inkscape must be installed. See the Ti*k*Z section
+for details.
+
+Ensure that the Asymptote `asy` binary is in the path, or point
+the environment variable `ASYMPTOTE` or the metadata variable
+`asymptotePath` to the full path name. Asymptote calls the various
+TeX utilities and dvipdfm, so you will need to configure Asymptote
+so that it finds them.
+
+```{.asymptote caption="This is an image, created by **Asymptote**."}
+size(5cm);
+include graph;
+
+pair circumcenter(pair A, pair B, pair C)
+{
+  pair P, Q, R, S;
+  P = (A+B)/2;
+  Q = (B+C)/2;
+  R = rotate(90, P) * A;
+  S = rotate(90, Q) * B;
+  return extension(P, R, Q, S);
+}
+
+pair incenter(pair A, pair B, pair C)
+{
+  real a = abs(angle(C-A)-angle(B-A)),
+       b = abs(angle(C-B)-angle(A-B)),
+       c = abs(angle(A-C)-angle(B-C));
+  return (sin(a)*A + sin(b)*B + sin(c)*C) / (sin(a)+sin(b)+sin(c));
+}
+
+real dist_A_BC(pair A, pair B, pair C)
+{
+  real det = cross(B-A, C-A);
+  return abs(det/abs(B-C));
+}
+
+pair A = (0, 0), B = (5, 0), C = (3.5, 4),
+     O = circumcenter(A, B, C),
+     I = incenter(A, B, C);
+dot(A); dot(B); dot(C); dot(O, blue); dot(I, magenta);
+draw(A--B--C--cycle, linewidth(2));
+draw(Circle(O, abs(A-O)), blue+linewidth(1.5));
+draw(Circle(I, dist_A_BC(I, A, B)), magenta+linewidth(1.5));
+label("$A$", A, SW);
+label("$B$", B, SE);
+label("$C$", C, NE);
+label("$O$", O, W);
+label("$I$", I, E);
+```
+
 ## How to run pandoc
 This section will show, how to call Pandoc in order to use this filter with
 meta keys. The following command assume, that the filters are stored in the
@@ -232,6 +292,7 @@ All available environment variables:
 - `JAVA_HOME` e.g. `c:\Program Files\Java\jre1.8.0_201`; Default: n/a
 - `DOT` e.g. `c:\ProgramData\chocolatey\bin\dot.exe`; Default: `dot`
 - `PDFLATEX` e.g. `c:\Program Files\MiKTeX 2.9\miktex\bin\x64\pdflatex.exe`; Default: `pdflatex`
+- `ASYMPTOTE` e.g. `c:\Program Files\Asymptote\asy`; Default: `asy`
 
 All available meta keys:
 
@@ -242,3 +303,4 @@ All available meta keys:
 - `java_path`
 - `dot_path`
 - `pdflatex_path`
+- `asymptote_path`