nika: v1
workflow:
  id: image-fx-batch
  description: "Folder of PNG files → deterministic art (grayscale · dither · pixelate) · offline batch"

vars:
  photos: "./photos" # the input folder · every .png in it gets the treatment

permits:
  exec: false
  fs:
    # a RELATIVE glob walks from `.` (the engine gates the walk root), so
    # the read boundary is the cwd subtree — and `const.photos` is caller-
    # overridable, so no narrower literal glob can be proven to cover it.
    # Fixing the folder? Tighten this to `photos/**`. The write stays tight
    read: ["**"]
    write: ["out/**"]
  tools: ["nika:glob", "nika:image_fx"]

tasks:
  # The folder is the work list — no hand-maintained array to drift.
  shots:
    invoke:
      tool: "nika:glob"
      args: { pattern: "${{ vars.photos }}/*.png" }

  # One deterministic darkroom pass per photo · the ops run IN ORDER.
  stylize:
    with:
      shots: ${{ tasks.shots.output }}
    for_each: ${{ with.shots }}
    max_parallel: 4
    invoke:
      tool: "nika:image_fx"
      args:
        input: "${{ item }}"
        ops:
          - grayscale: {}
          - dither: { mode: bayer4 }
          - pixelate: { block: 4 }
        out: "out/${{ item }}"

outputs:
  rendered:
    # an empty ./photos skips the fan-out (its output is null) — the guard
    # keeps the typed contract honest on the very first exploratory run
    value: "${{ tasks.stylize.output != null ? tasks.stylize.output : [] }}"
    description: "The stylized artifact receipts · one per input photo"

{"a":{"graph_format":2,"workflow":"image-fx-batch","nodes":[{"id":"shots","verb":"invoke","tool":"nika:glob","permits":["tool: nika:glob"]},{"id":"stylize","verb":"invoke","tool":"nika:image_fx","fan_out":{"kind":"expression"},"permits":["tool: nika:image_fx"]}],"edges":[{"from":"shots","to":"stylize","kind":"value"}]},"engine":"0.105.0"}

showcase · tier 1 · content

Image FX batch

glob lists the folder, for_each styles every photo through the same deterministic ops chain: no model, pure pixels.

The preset lives in git. Re-run in a year: byte-identical art, zero clicks. · conformance-gated in nika-spec ↗ · re-proven at every push

The whole file

2 tasks · 2 waves · the plan falls out of the bindings, nothing is scheduled by hand.

t1-image-fx-batch.nika.yamlsource

1nika: v12workflow:3  id: image-fx-batch4  description: "Folder of PNG files → deterministic art (grayscale · dither · pixelate) · offline batch"56vars:7  photos: "./photos" # the input folder · every .png in it gets the treatment89permits:10  ▷exec: false11  fs:12    # a RELATIVE glob walks from `.` (the engine gates the walk root), so13    # the read boundary is the cwd subtree — and `const.photos` is caller-14    # overridable, so no narrower literal glob can be proven to cover it.15    # Fixing the folder? Tighten this to `photos/**`. The write stays tight16    read: ["**"]17    write: ["out/**"]18  tools: ["nika:glob", "nika:image_fx"]1920tasks:21  # The folder is the work list — no hand-maintained array to drift.22  shots:23    ◆invoke:24      tool: "nika:glob"25      args: { pattern: "${{ vars.photos }}/*.png" }2627  # One deterministic darkroom pass per photo · the ops run IN ORDER.28  stylize:29    with:30      shots: ${{ tasks.shots.output }}31    for_each: ${{ with.shots }}32    max_parallel: 433    ◆invoke:34      tool: "nika:image_fx"35      args:36        input: "${{ item }}"37        ops:38          - grayscale: {}39          - dither: { mode: bayer4 }40          - pixelate: { block: 4 }41        out: "out/${{ item }}"4243outputs:44  rendered:45    # an empty ./photos skips the fan-out (its output is null) — the guard46    # keeps the typed contract honest on the very first exploratory run47    value: "${{ tasks.stylize.output != null ? tasks.stylize.output : [] }}"48    description: "The stylized artifact receipts · one per input photo"49

nika inspect · engine 0.105.0 · vendored graph, never re-derived

1 declared edge · 2 waves · the plan falls out of the bindings

try itopen in the playground guidethe walkthrough · docs verbinvoke toolnika:glob toolnika:image_fx