pxart put

put FILE[:frame] [-o OUT] < grid.txt

usage: pxart put [-h] [-o O] [--dry-run] target

  put FILE[:frame] [-o OUT] < grid.txt
      Replace one frame's grid with rows from stdin (palette lines first, optionally).

positional arguments:
  target

options:
  -h, --help  show this help message and exit
  -o O
  --dry-run   print what the edit says and a diff of the file it would change; write nothing

      Replace one frame's grid with the rows on stdin. Stdin is rows, or palette lines then
      rows; the keys the rows use join FILE's palette the way compose's layers do (a key
      FILE has in another color is E_KEY_CONFLICT), and other keys must be FILE's. Rows are
      checked like a file's (widths, keys), errors point at stdin's lines, and
      nothing is written on an error. Only that frame's lines change.
      A frame that doesn't exist yet is added, placed like new; a new FILE is started.
      Stdin has no variants: a key in FILE's color is FILE's key, variant colors and all, and
      a new key stays at its base color in FILE's variants.

See also, in pxart help all: compose (OUT's palette, frame placement, E_KEY_CONFLICT,
  --rekey); EDITING (-o OUT gets the whole file, only changed lines are rewritten, 'no
  change'); FORMAT: selecting frames (FILE:SEL, an unnamed grid's name, zsh's "${F}:sel").

pxart help all has the whole reference, pxart help TOPIC one part of it.

This is the output of pxart help put. The other editing commands and their shared notes are in pxart help EDITING.