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+% language=us
+
+\environment luametafun-style
+
+\startcomponent luametafun-contour
+
+\startchapter[title={Contour}]
+
+This feature started out as experiment triggered by a request on the mailing
+list. In the end it was a nice exploration of what is possible with a bit of
+\LUA. In a sense it is more subsystem than a simple \METAPOST\ macro because
+quite some \LUA\ code is involved and more might be used in the future. It's part
+of the fun.
+
+A contour is a line through equivalent values $z$ that result from applying a
+function to two variables $x$ and $y$. There is quite a bit of analysis needed
+to get these lines. In \METAFUN\ we currently support three methods for generating
+a colorful background and three for putting lines on top:
+
+One solution is to use the the isolines and isobands methods are described on the
+marching squares page of wikipedia:
+
+\starttyping
+https://en.wikipedia.org/wiki/Marching_squares
+\stoptyping
+
+This method is relative efficient as we don't do much optimization, simply
+because it takes time and the gain is not that much relevant. Because we support
+filling of multiple curves in one go, we get efficient paths anyway without side
+effects that normally can occur from many small paths alongside. In these days of
+multi megabyte movies and sound clips a request of making a \PDF\ file small is kind
+of strange anyway. In practice the penalty is not that large.
+
+As background we can use a bitmap. This method is also quite efficient because we
+use indexed colors which results in a very good compression. We use a simple
+mapping on a range of values.
+
+A third method is derived from the one that is distributed as \CCODE\ source
+file at:
+
+\starttyping
+https://physiology.arizona.edu/people/secomb/contours
+https://github.com/secomb/GreensV4
+\stoptyping
+
+We can create a background image, which uses a sequence of closed curves
+\footnote {I have to figure out how to improve it a bit so that multiple path
+don't get connected.}. It can also provide two variants of lines around the
+contours (we tag them shape and shade). It's all a matter of taste. In the
+meantime I managed to optimize the code a bit and I suppose that when I buy a new
+computer (the code was developed on an 8 year old machine) performance is
+probably acceptable.
+
+In order of useability you can think of isoband (band) with isolines (cell),
+bitmap (bitmap) with isolines (cell) and finally shapes (shape) with edges
+(edge). But let's start with a couple of examples.
+
+\startbuffer[1]
+\startMPcode{doublefun}
+ draw lmt_contour [
+ xmin = 0, xmax = 4*pi, xstep = .05,
+ ymin = -6, ymax = 6, ystep = .05,
+
+ levels = 7,
+ height = 5cm,
+ preamble = "local sin, cos = math.sin, math.cos",
+ function = "cos(x) + sin(y)",
+ background = "bitmap",
+ foreground = "edge",
+ linewidth = 1/2,
+ cache = true,
+ ] ;
+\stopMPcode
+\stopbuffer
+
+\startplacefigure[reference=contour:1]
+ \getbuffer[1]
+\stopplacefigure
+
+\typebuffer[1][option=TEX]
+
+In \in {figure} [contour:1] we see the result. There is a in this case black and
+white image generated and on top of that we see lines. The step determines the
+resolution of the image. In practice using a bitmap is quite okay and also rather
+efficient: we use an indexed colorspace and, as already was mentioned, because
+the number of colors is limited such an image compresses well. A different
+rendering is seen in \in {figure} [contour:2] where we use the shape method for
+the background. That method creates outlines but is much slower, and when you use
+a high resolution (small step) it can take quite a while to identify the shapes.
+This is why we set the cache flag.
+
+\startbuffer[2]
+\startMPcode{doublefun}
+ draw lmt_contour [
+ xmin = 0, xmax = 4*pi, xstep = .10,
+ ymin = -6, ymax = 6, ystep = .10,
+
+ levels = 7,
+ preamble = "local sin, cos = math.sin, math.cos",
+ function = "cos(x) - sin(y)",
+ background = "shape",
+ foreground = "shape",
+ linewidth = 1/2,
+ cache = true,
+ ] ;
+\stopMPcode
+\stopbuffer
+
+\typebuffer[2][option=TEX]
+
+\startplacefigure[reference=contour:2]
+ \getbuffer[2]
+\stopplacefigure
+
+We mentioned colorspace but haven't seen any color yet, so let's set some in \in
+{figure} [contour:3]. Two variants are shown: a background \type {shape} with
+foreground \type {shape} and a background \type {bitmap} with a foreground \type
+{edge}. The bitmap renders quite fast, definitely when we compare with the shape,
+while the quality is as good at this size.
+
+\startbuffer[3a]
+\startMPcode{doublefun}
+ draw lmt_contour [
+ xmin = -10, xmax = 10, xstep = .1,
+ ymin = -10, ymax = 10, ystep = .1,
+
+ levels = 10,
+ height = 7cm,
+ color = "shade({1/2,1/2,0},{0,0,1/2})",
+ function = "x^2 + y^2",
+ background = "shape",
+ foreground = "shape",
+ linewidth = 1/2,
+ cache = true,
+ ] xsized .45TextWidth ;
+\stopMPcode
+\stopbuffer
+
+\startbuffer[3b]
+\startMPcode{doublefun}
+ draw lmt_contour [
+ xmin = -10, xmax = 10, xstep = .1,
+ ymin = -10, ymax = 10, ystep = .1,
+
+ levels = 10,
+ height = 7cm,
+ color = "shade({1/2,0,0},{0,0,1/2})",
+ function = "x^2 + y^2",
+ background = "bitmap",
+ foreground = "edge",
+ linewidth = 1/2,
+ cache = true,
+ ] xsized .45TextWidth ;
+\stopMPcode
+\stopbuffer
+
+\typebuffer[3a][option=TEX]
+
+\startplacefigure[reference=contour:3]
+ \startcombination
+ {\getbuffer[3a]} {\bf shape}
+ {\getbuffer[3b]} {\bf bitmap}
+ \stopcombination
+\stopplacefigure
+
+We use the \type {doublefun} instance because we need to be sure that we don't
+run into issues with scaled numbers, the default model in \METAPOST. The
+function that gets passed is {\em not} using \METAPOST\ but \LUA, so basically
+you can do very complex things. Here we directly pass code, but you can for
+instance also do this:
+
+\starttyping[option=TEX]
+\startluacode
+ function document.MyContourA(x,y)
+ return x^2 + y^2
+ end
+\stopluacode
+\stoptyping
+
+and then \type {function = "document.MyContourA(x,y)"}. As long as the function
+returns a valid number we're okay. When you pass code directly you can use the
+\type {preamble} key to set local shortcuts. In the previous examples we took
+\type {sin} and \type {cos} from the math library but you can also roll out your
+own functions and|/|or use the more elaborate \type {xmath} library. The color
+parameter is also a function, one that returns one or three arguments. In the
+next example we use \type {lin} to calculate a fraction of the current level and
+total number of levels.
+
+\startbuffer[4a]
+\startMPcode{doublefun}
+ draw lmt_contour [
+ xmin = -3, xmax = 3, xstep = .01,
+ ymin = -1, ymax = 1, ystep = .01,
+
+ levels = 10,
+ default = .5,
+ height = 5cm,
+ function = "x^2 + y^2 + x + y/2",
+ color = "lin(l), 0, 1/2",
+ background = "bitmap"
+ foreground = "none",
+ cache = true,
+ ] xsized TextWidth ;
+\stopMPcode
+\stopbuffer
+
+\typebuffer[4a][option=TEX]
+
+\startplacefigure[reference=contour:4a]
+ \getbuffer[4a]
+\stopplacefigure
+
+Instead of a bitmap we can use an isoband, which boils down to a set of tiny
+shapes that make up a bigger one. This is shown in \in {figure} [contour:4b].
+
+\startbuffer[4b]
+\startMPcode{doublefun}
+ draw lmt_contour [
+ xmin = -3, xmax = 3, xstep = .01,
+ ymin = -1, ymax = 1, ystep = .01,
+
+ levels = 10,
+ default = .5,
+ height = 5cm,
+ function = "x^2 + y^2 + x + y/2",
+ color = "lin(l), 1/2, 0",
+ background = "band",
+ foreground = "none",
+ cache = true,
+ ] xsized TextWidth ;
+\stopMPcode
+\stopbuffer
+
+\typebuffer[4b][option=TEX]
+
+\startplacefigure[reference=contour:4b]
+ \getbuffer[4b]
+\stopplacefigure
+
+You can draw several functions and see where they overlap:
+
+\startbuffer[5]
+\startMPcode{doublefun}
+ draw lmt_contour [
+ xmin = -pi, xmax = 4*pi, xstep = .1,
+ ymin = -3, ymax = 3, ystep = .1,
+
+ range = { -.1, .1 },
+ preamble = "local sin, cos = math.sin, math.cos",
+ functions = {
+ "sin(x) + sin(y)", "sin(x) + cos(y)",
+ "cos(x) + sin(y)", "cos(x) + cos(y)"
+ },
+ background = "bitmap",
+ linecolor = "black",
+ linewidth = 1/10,
+ color = "shade({1,1,0},{0,0,1})"
+ cache = true,
+ ] xsized TextWidth ;
+\stopMPcode
+\stopbuffer
+
+\typebuffer[5][option=TEX]
+
+\startplacefigure[reference=contour:5]
+ \getbuffer[5]
+\stopplacefigure
+
+The range determines the $z$ value(s) that we take into account. You can also
+pass a list of colors to be used. In \in {figure} [contour:6] this is
+demonstrated. There we also show a variant foreground \type {cell}, which uses a
+bit different method for calculating the edges. \footnote {This a bit of a
+playground: more variants might show up in due time.}
+
+\startbuffer[6]
+\startMPcode{doublefun}
+ draw lmt_contour [
+ xmin = -2*pi, xmax = 2*pi, xstep = .01,
+ ymin = -3, ymax = 3, ystep = .01,
+
+ range = { -.1, .1 },
+ preamble = "local sin, cos = math.sin, math.cos",
+ functions = { "sin(x) + sin(y)", "sin(x) + cos(y)" },
+ background = "bitmap",
+ foreground = "cell",
+ linecolor = "white",
+ linewidth = 1/10,
+ colors = { (1/2,1/2,1/2), red, green, blue }
+ level = 3,
+ linewidth = 6,
+ cache = true,
+ ] xsized TextWidth ;
+\stopMPcode
+\stopbuffer
+
+\typebuffer[6][option=TEX]
+
+Here the number of levels depends on the number of functions as each can overlap
+with another; for instance the outcome of two functions can overlap or not which
+means 3 cases, and with a value not being seen that gives 4 different cases.
+
+\startplacefigure[reference=contour:6]
+ \getbuffer[6]
+\stopplacefigure
+
+\startbuffer[7]
+\startMPcode{doublefun}
+ draw lmt_contour [
+ xmin = -2*pi, xmax = 2*pi, xstep = .01,
+ ymin = -3, ymax = 3, ystep = .01,
+
+ range = { -.1, .1 },
+ preamble = "local sin, cos = math.sin, math.cos",
+ functions = {
+ "sin(x) + sin(y)",
+ "sin(x) + cos(y)",
+ "cos(x) + sin(y)",
+ "cos(x) + cos(y)"
+ },
+ background = "bitmap",
+ foreground = "none",
+ level = 3,
+ color = "shade({2/3,0,0},{2/3,1,2/3})"
+ cache = true,
+ ] xsized TextWidth ;
+\stopMPcode
+\stopbuffer
+
+\typebuffer[7][option=TEX]
+
+Of course one can wonder how useful showing many functions but it can give nice
+pictures, as shown in \in {figure} [contour:7].
+
+\startplacefigure[reference=contour:7]
+ \getbuffer[7]
+\stopplacefigure
+
+\startbuffer[8]
+\startMPcode{doublefun}
+ draw lmt_contour [
+ xmin = -2*pi, xmax = 2*pi, xstep = .01,
+ ymin = -3, ymax = 3, ystep = .01,
+
+ range = { -.3, .3 },
+ preamble = "local sin, cos = math.sin, math.cos",
+ functions = {
+ "sin(x) + sin(y)",
+ "sin(x) + cos(y)",
+ "cos(x) + sin(y)",
+ "cos(x) + cos(y)"
+ },
+ background = "bitmap",
+ foreground = "none",
+ level = 3,
+ color = "shade({1,0,0},{0,1,0})"
+ cache = true,
+ ] xsized TextWidth ;
+\stopMPcode
+\stopbuffer
+
+\typebuffer[8][option=TEX]
+
+We can enlargen the window, which is demonstrated in \in {figure} [contour:8]. I
+suppose that such images only make sense in educational settings.
+
+\startplacefigure[reference=contour:8]
+ \getbuffer[8]
+\stopplacefigure
+
+% \startbuffer[9a]
+% \startMPcode{doublefun}
+% draw lmt_contour [
+% xmin = -10, xmax = 10, xstep = 1,
+% ymin = -10, ymax = 10, ystep = 1,
+% function = "math.random(1,3)", levels = 3,
+% linecolor = "white", linewidth = 1/10,
+% width = .3TextWidth, legend = "none",
+% color = "shade({1/2,1/2,0},{0,0,1})"
+%
+% background = "bitmap", foreground = "edge",
+% ] ;
+% \stopMPcode
+% \stopbuffer
+%
+% \typebuffer[9a][option=TEX]
+%
+% \startbuffer[9b]
+% \startMPcode{doublefun}
+% draw lmt_contour [
+% xmin = -10, xmax = 10, xstep = 1,
+% ymin = -10, ymax = 10, ystep = 1,
+% function = "math.random(1,3)", levels = 3,
+% linecolor = "white", linewidth = 1/10,
+% width = .3TextWidth, legend = "none",
+% color = "shade({1/2,1/2,0},{0,0,1/2})"
+%
+% background = "bitmap", foreground = "cell",
+% ] ;
+% \stopMPcode
+% \stopbuffer
+%
+% \startbuffer[9c]
+% \startMPcode{doublefun}
+% draw lmt_contour [
+% xmin = -10, xmax = 10, xstep = 1,
+% ymin = -10, ymax = 10, ystep = 1,
+% function = "math.random(1,3)", levels = 3,
+% linecolor = "white", linewidth = 1/10,
+% width = .3TextWidth, legend = "none",
+% color = "shade({1/2,1/2,0},{0,0,1})"
+%
+% background = "bitmap", foreground = "none",
+% ] ;
+% \stopMPcode
+% \stopbuffer
+%
+% \startbuffer[9d]
+% \startMPcode{doublefun}
+% draw lmt_contour [
+% xmin = -10, xmax = 10, xstep = 1,
+% ymin = -10, ymax = 10, ystep = 1,
+% function = "math.random(1,3)", levels = 3,
+% linecolor = "white", linewidth = 1/10,
+% width = .3TextWidth, legend = "none",
+% color = "shade({1/2,1/2,0},{0,0,1})"
+%
+% background = "shape", foreground = "shape",
+% ] ;
+% \stopMPcode
+% \stopbuffer
+%
+% \startbuffer[9e]
+% \startMPcode{doublefun}
+% draw lmt_contour [
+% xmin = -10, xmax = 10, xstep = 1,
+% ymin = -10, ymax = 10, ystep = 1,
+% function = "math.random(1,3)", levels = 3,
+% linecolor = "white", linewidth = 1/10,
+% width = .3TextWidth, legend = "none",
+% color = "shade({1/2,1/2,0},{0,0,1})"
+%
+% background = "shape", foreground = "edge",
+% ] ;
+% \stopMPcode
+% \stopbuffer
+%
+% \startbuffer[9f]
+% \startMPcode{doublefun}
+% draw lmt_contour [
+% xmin = -10, xmax = 10, xstep = 1,
+% ymin = -10, ymax = 10, ystep = 1,
+% function = "math.random(1,3)", levels = 3,
+% linecolor = "white", linewidth = 1/10,
+% width = .3TextWidth, legend = "none",
+% color = "shade({1/2,1/2,0},{0,0,1})"
+%
+% background = "shape", foreground = "none",
+% ] ;
+% \stopMPcode
+% \stopbuffer
+%
+% \startbuffer[9g]
+% \startMPcode{doublefun}
+% draw lmt_contour [
+% xmin = -10, xmax = 10, xstep = 1,
+% ymin = -10, ymax = 10, ystep = 1,
+% function = "math.random(1,3)", levels = 3,
+% linecolor = "white", linewidth = 1/10,
+% width = .3TextWidth, legend = "none",
+% color = "shade({1/2,1/2,0},{0,0,1})"
+%
+% background = "band", foreground = "edge",
+% ] ;
+% \stopMPcode
+% \stopbuffer
+%
+% \startbuffer[9h]
+% \startMPcode{doublefun}
+% draw lmt_contour [
+% xmin = -10, xmax = 10, xstep = 1,
+% ymin = -10, ymax = 10, ystep = 1,
+% function = "math.random(1,3)", levels = 3,
+% linecolor = "white", linewidth = 1/10,
+% width = .3TextWidth, legend = "none",
+% color = "shade({1/2,1/2,0},{0,0,1})"
+%
+% background = "band", foreground = "cell",
+% ] ;
+% \stopMPcode
+% \stopbuffer
+%
+% \startbuffer[9i]
+% \startMPcode{doublefun}
+% draw lmt_contour [
+% xmin = -10, xmax = 10, xstep = 1,
+% ymin = -10, ymax = 10, ystep = 1,
+% function = "math.random(1,3)", levels = 3,
+% linecolor = "white", linewidth = 1/10,
+% width = .3TextWidth, legend = "none",
+% color = "shade({1/2,1/2,0},{0,0,1})"
+%
+% background = "band", foreground = "none",
+% ] ;
+% \stopMPcode
+% \stopbuffer
+%
+% In \in {figure} [contour:9] we see that using the shape option doesn't work out
+% too well here, which again demonstrates that using the bitmap method is not that
+% bad. In that example we use random numbers, just to show the erratic behavior. In
+% \in {figure} [contour:10] a more sane image is used. The band and bitmap examples
+% are generated quite fast so no caching is used there. We only show one definition:
+%
+% \typebuffer[9i][option=TEX]
+%
+% \startplacefigure[reference=contour:9]
+% \startcombination[3*3]
+% {\pushrandomseed\setrandomseed{1}\getbuffer[9a]\poprandomseed} {\bf bitmap edge}
+% {\pushrandomseed\setrandomseed{1}\getbuffer[9b]\poprandomseed} {\bf bitmap cell}
+% {\pushrandomseed\setrandomseed{1}\getbuffer[9c]\poprandomseed} {\bf bitmap none}
+% {\pushrandomseed\setrandomseed{1}\getbuffer[9d]\poprandomseed} {\bf shape shape}
+% {\pushrandomseed\setrandomseed{1}\getbuffer[9e]\poprandomseed} {\bf shape edge}
+% {\pushrandomseed\setrandomseed{1}\getbuffer[9f]\poprandomseed} {\bf shape none}
+% {\pushrandomseed\setrandomseed{1}\getbuffer[9g]\poprandomseed} {\bf band edge}
+% {\pushrandomseed\setrandomseed{1}\getbuffer[9h]\poprandomseed} {\bf band cell}
+% {\pushrandomseed\setrandomseed{1}\getbuffer[9i]\poprandomseed} {\bf band none}
+% \stopcombination
+% \stopplacefigure
+
+In \in {figure} [contour:10] we see different combinations of backgrounds (in color)
+and foregrounds (edges) in action.
+
+\startbuffer[10a]
+\startMPcode{doublefun}
+ draw lmt_contour [
+ xmin = 0, xmax = 4*pi, xstep = 0,
+ ymin = -6, ymax = 6, ystep = 0,
+
+ levels = 5, legend = false, linewidth = 1/2,
+
+ preamble = "local sin, cos = math.sin, math.cos",
+ function = "cos(x) - sin(y)",
+ color = "shade({1/2,0,0},{0,0,1/2})",
+
+ background = "bitmap", foreground = "edge",
+ ] xsized .3TextWidth ;
+\stopMPcode
+\stopbuffer
+
+\startbuffer[10b]
+\startMPcode{doublefun}
+ draw lmt_contour [
+ xmin = 0, xmax = 4*pi, xstep = 0,
+ ymin = -6, ymax = 6, ystep = 0,
+
+ levels = 5, legend = false, linewidth = 1/2,
+
+ preamble = "local sin, cos = math.sin, math.cos",
+ function = "cos(x) - sin(y)",
+ color = "shade({1/2,0,0},{0,0,1/2})",
+
+ background = "bitmap", foreground = "cell",
+ ] xsized .3TextWidth ;
+\stopMPcode
+\stopbuffer
+
+\startbuffer[10c]
+\startMPcode{doublefun}
+ draw lmt_contour [
+ xmin = 0, xmax = 4*pi, xstep = 0,
+ ymin = -6, ymax = 6, ystep = 0,
+
+ levels = 5, legend = false, linewidth = 1/2,
+
+ preamble = "local sin, cos = math.sin, math.cos",
+ function = "cos(x) - sin(y)",
+ color = "shade({1/2,0,0},{0,0,1/2})",
+
+ background = "bitmap", foreground = "none",
+ ] xsized .3TextWidth ;
+\stopMPcode
+\stopbuffer
+
+\startbuffer[10d]
+\startMPcode{doublefun}
+ draw lmt_contour [
+ xmin = 0, xmax = 4*pi, xstep = 0,
+ ymin = -6, ymax = 6, ystep = 0,
+
+ levels = 5, legend = false, linewidth = 1/2,
+
+ preamble = "local sin, cos = math.sin, math.cos",
+ function = "cos(x) - sin(y)",
+ color = "shade({1/2,0,0},{0,0,1/2})",
+
+ background = "shape", foreground = "shape", cache = true,
+ ] xsized .3TextWidth ;
+\stopMPcode
+\stopbuffer
+
+\startbuffer[10e]
+\startMPcode{doublefun}
+ draw lmt_contour [
+ xmin = 0, xmax = 4*pi, xstep = 0,
+ ymin = -6, ymax = 6, ystep = 0,
+
+ levels = 5, legend = false, linewidth = 1/2,
+
+ preamble = "local sin, cos = math.sin, math.cos",
+ function = "cos(x) - sin(y)",
+ color = "shade({1/2,0,0},{0,0,1/2})",
+
+ background = "shape", foreground = "edge", cache = true,
+ ] xsized .3TextWidth ;
+\stopMPcode
+\stopbuffer
+
+\startbuffer[10f]
+\startMPcode{doublefun}
+ draw lmt_contour [
+ xmin = 0, xmax = 4*pi, xstep = 0,
+ ymin = -6, ymax = 6, ystep = 0,
+
+ levels = 5, legend = false, linewidth = 1/2,
+
+ preamble = "local sin, cos = math.sin, math.cos",
+ function = "cos(x) - sin(y)",
+ color = "shade({1/2,0,0},{0,0,1/2})",
+
+ background = "shape", foreground = "none", cache = true,
+ ] xsized .3TextWidth ;
+\stopMPcode
+\stopbuffer
+
+\startbuffer[10g]
+\startMPcode{doublefun}
+ draw lmt_contour [
+ xmin = 0, xmax = 4*pi, xstep = 0,
+ ymin = -6, ymax = 6, ystep = 0,
+
+ levels = 5, legend = false, linewidth = 1/2,
+
+ preamble = "local sin, cos = math.sin, math.cos",
+ function = "cos(x) - sin(y)",
+ color = "shade({1/2,0,0},{0,0,1/2})",
+
+ background = "band", foreground = "edge",
+ ] xsized .3TextWidth ;
+\stopMPcode
+\stopbuffer
+
+\startbuffer[10h]
+\startMPcode{doublefun}
+ draw lmt_contour [
+ xmin = 0, xmax = 4*pi, xstep = 0,
+ ymin = -6, ymax = 6, ystep = 0,
+
+ levels = 5, legend = false, linewidth = 1/2,
+
+ preamble = "local sin, cos = math.sin, math.cos",
+ function = "cos(x) - sin(y)",
+ color = "shade({1/2,0,0},{0,0,1/2})",
+
+ background = "band", foreground = "cell",
+ ] xsized .3TextWidth ;
+\stopMPcode
+\stopbuffer
+
+\startbuffer[10i]
+\startMPcode{doublefun}
+ draw lmt_contour [
+ xmin = 0, xmax = 4*pi, xstep = 0,
+ ymin = -6, ymax = 6, ystep = 0,
+
+ levels = 5, legend = false, linewidth = 1/2,
+
+ preamble = "local sin, cos = math.sin, math.cos",
+ function = "cos(x) - sin(y)",
+ color = "shade({1/2,0,0},{0,0,1/2})",
+
+ background = "band", foreground = "none",
+ ] xsized .3TextWidth ;
+\stopMPcode
+\stopbuffer
+
+\typebuffer[10b][option=TEX]
+
+% \page
+
+There are quite some settings. Some deal with the background, some with the
+foreground and quite some deal with the legend.
+
+\starttabulate[|T|T|T|p|]
+\FL
+\BC name \BC type \BC default \BC comment \NC \NR
+\ML
+\NC xmin \NC numeric \NC 0 \NC needs to be set \NC \NR
+\NC xmax \NC numeric \NC 0 \NC needs to be set \NC \NR
+\NC ymin \NC numeric \NC 0 \NC needs to be set \NC \NR
+\NC ymax \NC numeric \NC 0 \NC needs to be set \NC \NR
+\NC xstep \NC numeric \NC 0 \NC auto 1/200 when zero \NC \NR
+\NC ystep \NC numeric \NC 0 \NC auto 1/200 when zero \NC \NR
+\NC checkresult \NC boolean \NC false \NC checks for overflow and NaN \NC \NR
+\NC defaultnan \NC numeric \NC 0 \NC the value to be used when NaN \NC \NR
+\NC defaultinf \NC numeric \NC 0 \NC the value to be used when overflow \NC \NR
+\ML
+\NC levels \NC numeric \NC 10 \NC number of different levels to show \NC \NR
+\NC level \NC numeric \NC \NC only show this level (foreground) \NC \NR
+\ML
+\NC preamble \NC string \NC \NC shortcuts \NC \NR
+\NC function \NC string \NC x + y \NC the result z value \NC \NR
+\NC functions \NC list \NC \NC multiple functions (overlapping levels) \NC \NR
+\NC color \NC string \NC lin(l) \NC the result color value for level l (1 or 3 values) \NC \NR
+\NC colors \NC numeric \NC \NC used when set \NC \NR
+\ML
+\NC background \NC string \NC bitmap \NC band, bitmap, shape \NC \NR
+\NC foreground \NC string \NC auto \NC cell, edge, shape auto \NC \NR
+\ML
+\NC linewidth \NC numeric \NC .25 \NC \NC \NR
+%NC backgroundcolor \NC string \NC black \NC \NC \NR
+\NC linecolor \NC string \NC gray \NC \NC \NR
+\ML
+\NC width \NC numeric \NC 0 \NC automatic when zero \NC \NR
+\NC height \NC numeric \NC 0 \NC automatic when zero \NC \NR
+\ML
+\NC trace \NC boolean \NC false \NC \NC \NR
+\ML
+\NC legend \NC string \NC all \NC x y z function range all \NC \NR
+\NC legendheight \NC numeric \NC LineHeight \NC \NC \NR
+\NC legendwidth \NC numeric \NC LineHeight \NC \NC \NR
+\NC legendgap \NC numeric \NC 0 \NC \NC \NR
+\NC legenddistance \NC numeric \NC EmWidth \NC \NC \NR
+\NC textdistance \NC numeric \NC 2EmWidth/3 \NC \NC \NR
+\NC functiondistance \NC numeric \NC ExHeight \NC \NC \NR
+\NC functionstyle \NC string \NC \NC \CONTEXT\ style name \NC \NR
+\NC xformat \NC string \NC @0.2N \NC number format template \NC \NR
+\NC yformat \NC string \NC @0.2N \NC number format template \NC \NR
+\NC zformat \NC string \NC @0.2N \NC number format template \NC \NR
+\NC xstyle \NC string \NC \NC \CONTEXT\ style name \NC \NR
+\NC ystyle \NC string \NC \NC \CONTEXT\ style name \NC \NR
+\NC zstyle \NC string \NC \NC \CONTEXT\ style name \NC \NR
+\ML
+\NC axisdistance \NC numeric \NC ExHeight \NC \NC \NR
+\NC axislinewidth \NC numeric \NC .25 \NC \NC \NR
+\NC axisoffset \NC numeric \NC ExHeight/4 \NC \NC \NR
+\NC axiscolor \NC string \NC black \NC \NC \NR
+\NC ticklength \NC numeric \NC ExHeight \NC \NC \NR
+\ML
+\NC xtick \NC numeric \NC 5 \NC \NC \NR
+\NC ytick \NC numeric \NC 5 \NC \NC \NR
+\NC xlabel \NC numeric \NC 5 \NC \NC \NR
+\NC ylabel \NC numeric \NC 5 \NC \NC \NR
+\LL
+\stoptabulate
+
+\startplacefigure[reference=contour:10]
+ \startcombination[3*3]
+ {\getbuffer[10a]} {\bf bitmap edge}
+ {\getbuffer[10b]} {\bf bitmap cell}
+ {\getbuffer[10c]} {\bf bitmap none}
+ {\getbuffer[10d]} {\bf shape shape}
+ {\getbuffer[10e]} {\bf shape edge}
+ {\getbuffer[10f]} {\bf shape none}
+ {\getbuffer[10g]} {\bf band edge}
+ {\getbuffer[10h]} {\bf band cell}
+ {\getbuffer[10i]} {\bf band none}
+ \stopcombination
+\stopplacefigure
+
+\stopchapter
+
+\stopcomponent
generated by cgit v1.2.3 (git 2.25.1) at 2024-05-05 14:37:43 +0000