trace output of a run of npiet with the -tpic option set: input was hi.png (in pixelsize resolution: ).

(bigger pic)

some words about the stuff you see (please refer to the piet page about details of the language and the execution):

the execution starts always in the uppler left codel (the execution path starts at the dot there).

the direction pointer (dp) and the codel chooser (cc) are printed with the step tried; eg: try=0, with dp=right, cc=left as 0 r l (in higher resolution this is printed formatted and more verbose with the trace step; eg. step 12, try 3, dp=up and cc=right as 12.3 u/r).

the first try (go dp=right from cc=left - the arrow painted there indicates that) is successful, we enter the dark blue codel from the normal blue (this is zero change in cue color and 1 in lightness: the command to execute is a push of the value 9.

now i think you get the picture:

next step is step 1 and the first try 0 to continue is r/l.

ok, but this way is blocked by a black codel. so cc is toggled and the next try is 1 with dp and cc both right: r/r.

this is successful and we execute again a push, this time with the value 8 and continuing from the light blue codel.

but now you have to go on yourself, until...

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Thu Jun 10 22:31:52 CEST 2004