Dear Hans,

I read the “luametafun.pdf” and run the codes one by one.
It is a really nice to have those figures easily.

During the reading, I found that there is a difference between the figure in the manual and the output of my run.
I run the following code at page 24-25 in “luametafun.pdf”.

\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) + cos(y)"
background = "bitmap",
foreground = "edge", 
linewidth = 1/2, 
cache = true,
]; 
\stopMPcode


In the output, the background of text is gray while the background of text in the manual is white.
Here are versions of LuaMetaTeX and ConTeXt which I use.

%%%%%%%
This is LuaMetaTeX, Version 2.03.4 
open source     > level 1, order 1, name 'cont-yes.mkiv'
system          > 
system          > ConTeXt  ver: 2019.12.16 18:54 MKIV beta  fmt: 2019.12.17  int: english/english
system          > 
%%%%%%%%%

Is there anything that I miss?
Would you please to check it?

Thank you.

Best regards,

Dalyoung