mfpic-doc.pdf.

4.12 FOR ADVANCED USERS. 70
... }. Tiling an open curve is technically an error, but the METAFONT code responds by drawing
the path and not doing any tiling. The METAFONT code places shifted copies of the tile picture in a
rectangular grid sufficient to cover the region, then clips it to the closed path before drawing it.
Tiling large regions with complicated tiles can exceed the capacity of some versions of META-
POST. There is less of a problem with METAFONT. This is not because METAFONT has greater
capacity, but because of the natural difference between bitmaps and vector graphics.
In METAPOST, the tiles are copied with whatever color they are given when they are defined.
They can be multicolored.
Before version 0.8, \tile was the only way to create a picture variable, and the only way to
draw this picture was with the \tess command. Now we have the following command to place
multiple copies of a picture:
\putmfpimage{〈name〉}{〈list〉}
This take the name of a picture variable and copies the picture at each location in the 〈list〉, which
should be a comma-separated list of coordinate pairs in graph coordinates. The picture is copied so
that its reference point is placed at each of the locations. The reference point of a picture created
with \tile is its lower left corner.
\mfpimage[〈refpt〉]{〈picname〉}
〈MFPIC drawing commands〉
\endmfpimage
This is another way to create a picture variable. The drawing commands within the mfpimage
environment contribute not to the current MFPIC picture, but rather to the picture variable named in
〈picname〉. Otherwise, they operate exactly as they would outside this environment, using the same
coordinate system and the same default values of all parameters, etc. (unlike the tile environment,
which defines its own coordinate system). The picture is created with its reference point at the point
〈refpt〉 given in the optional argument. The default is (0,0). For example:
\mfpimage[(1,1)]{Jan}
\fill\rect{(0,0),(1,1)}
\fill\rect{(1,1),(2,2)}
\rect{(0,0),(2,2)}
\endmfpimage
produces a simple 2-by-2 chessboard with its reference point at the center point (1,1). One can then
write something like
\putmfpimage{Jan}{(1,1),(3,1),(1,3),(3,3)}
to get a 4-by-4 chessboard: the picture Jan copied with its center at each of the listed points.
The behavior of \tlabel in an mfpimage environment depends on the setting. If mplabels is
turned off, then labels are added by TEX and are not included as part of the named METAFONT or
METAPOST picture variable. They are placed on the current picture as if the mfpimage environment
were not there at all. If mplabels is turned on and overlaylabels is also turned on, or if the mfpimage
environment is between \startbacktext and \stopbacktext, then the labels will be saved and
placed when the mfpic environment ends and not added to the named picture variable. Thus, to
include text labels in the named picture variable, you must have mplabels on, overlaylabels off, and
mfpimage outside any \startbacktext/\stopbacktext.
The picture created by \mfpimage is locally defined. That is, it becomes undefined at the end of
the current mfpic environment. If one needs it to be global, one can use \globalsetmfvariable
(see subsection 4.12.4) to copy it to another variable. For example. the command