> ## Documentation Index > Fetch the complete documentation index at: https://docs.nika.sh/llms.txt > Use this file to discover all available pages before exploring further. # Image effects > Deterministic artistic styling — dither, palettes, halftone, retro, glitch, ascii. Same input, same args, same bytes forever: the styled image becomes a receipt in the run's proof chain. `nika:image_fx` is the deterministic sibling of [`nika:image_generate`](/guides/image-generation): a pure pixel transform — no provider, no network, no clock. Style a PNG through an ordered pipeline of effects and get an artifact that is **byte-identical forever** for identical `(input, args)`. That determinism is the point, not a detail. The artifact's sha256 joins the run's hash-chained trace, re-rendering the recipe is the tamper check, and the full recipe (contract tag `image_fx/v1` · input sha256 · seed · ops) travels *inside* the PNG as a `nika` tEXt chunk — no timestamp, ever. Your workflow draws its own receipts. ## The 30-second pipeline ```yaml theme={"system"} nika: v1 workflow: styled-hero permits: tools: ["nika:image_generate", "nika:image_fx"] fs: read: ["out/**"] write: ["out/**"] tasks: - id: generate invoke: tool: "nika:image_generate" args: provider: mock # offline dry-run · flip to local/openai/gemini/xai prompt: "a monarch butterfly over a nebula" output_dir: out format: png - id: style depends_on: [generate] invoke: tool: "nika:image_fx" args: input: "${{ tasks.generate.output.images[0].path }}" out: out/hero-gameboy.png seed: 42 # the seed IS the style — same seed, same bytes ops: - resize: { width: 320 } - dither: { mode: floyd_steinberg, palette: gameboy } - grain: { intensity: 32 } - scanlines: { strength: 110, period: 4 } - vignette: { strength: 140 } ``` Run it twice: the second run reports `skipped_existing: true` and the artifact hash never moves. Mutate one byte of the PNG and a re-render no longer matches — that mismatch *is* the tamper detection. ## The op vocabulary (closed · v1) `ops:` is an **ordered list of single-key maps** — a linear pipeline by design. Branching and fan-out belong to the workflow (`depends_on` · `for_each`), never inside the builtin. | Op | What it does | Key knobs | | ---------------------- | ----------------------------------------------- | ------------------------------------------------------------------------------------------- | | `resize` | Linear-light resample | `width`/`height` (one may be omitted) · `filter: auto\|nearest\|bilinear` | | `crop` | Exact rectangle | `x` · `y` · `width` · `height` | | `levels` | Brightness / contrast | `brightness` −255..255 · `contrast` −128..128 | | `grayscale` | Linear-light luma | — | | `palette_map` | Nearest palette color (Oklab distance) | `palette` | | `dither` | Quantize through a dither | `mode: bayer2\|bayer4\|bayer8\|blue_noise\|ign\|floyd_steinberg\|atkinson\|jjn` · `palette` | | `duotone` | Two-stop gradient map (Oklab ramp) | `dark` · `light` (`#rrggbb` or `[r,g,b]`) | | `pixelate` | Block mosaic | `block` 2..256 | | `halftone` | Rotated clustered-dot screen (print look) | `cell` 3..64 · `angle: 0\|15\|45\|75` | | `grain` | Luminance-shaped film grain (seeded) | `intensity` 0..128 | | `vignette` | Natural cos⁴ falloff | `strength` 0..255 | | `chromatic_aberration` | Per-channel radial split | `shift` 1..16 | | `scanlines` | CRT row darkening | `strength` 0..255 · `period` 2..64 | | `glitch` | Seeded databending | `line_shift` ≤64 · `channel_shift` ≤16 · `blocks` ≤64 | | `ascii` | Character-grid render — **must be the last op** | `cols` 2..1024 · `emit: png\|text\|ansi` | Palettes: presets `bw · gray4 · gameboy · cga · okabe_ito`, or an inline list of 2–256 colors. Unknown op parameters are **rejected loudly** (`NIKA-BUILTIN-IMAGE_FX-001`) — a typo'd knob never silently lies about the style. Input is **PNG in v1** (depth 8 · no interlace). Non-PNG fails with a typed hint: produce PNG upstream (`image_generate` with `format: png`) or convert once via `exec:`. Decode is budget-gated from the header **before** any decompression — hostile dimension claims are rejected, never allocated. ## Why deterministic styling matters Every incumbent styling path is nondeterministic by default — image tools timestamp their outputs, and generative models can't reproduce bytes across hardware at all. That makes styled assets un-verifiable: you can sign them, but you can't *re-derive* them. `image_fx` inverts that: integer/fixed-point pixel math, a seeded noise stream, zero wall-clock. So the artifact can be: * **chained** — its sha256 lands in the trace (`nika trace verify` covers it); * **re-rendered** — the same input + the recipe reproduces the exact bytes; * **carried** — the recipe rides the artifact itself, so any holder of the input can verify the styling. One recipe, one hash, forever. Batch-style a hundred campaign images with `for_each` and every one of them is a receipt. ```yaml theme={"system"} - id: variants depends_on: [generate] for_each: ["bw", "gameboy", "cga"] invoke: tool: "nika:image_fx" args: input: "${{ tasks.generate.output.images[0].path }}" out: "out/variant-${{ item }}.png" ops: - dither: { mode: bayer4, palette: "${{ item }}" } ``` ## Output contract ```json theme={"system"} { "input": "out/hero.png", "input_sha256": "…", "path": "out/hero-gameboy.png", "sha256": "…", "size_bytes": 323953, "width": 320, "height": 200, "format": "png", "ops_applied": 5, "seed": 42, "skipped_existing": false } ``` Artifact bytes never ride outputs (the disk law). Text artifacts (`ascii` with `emit: text|ansi`) land as `.txt`/`.ans`, report `width`/`height` `0`, and are sha256'd like any other artifact. Errors are typed `NIKA-BUILTIN-IMAGE_FX-001..006` — invalid args · input read · unsupported format · decode · pixel budget · save — plus the boundary `NIKA-SEC-004` when a path resolves outside `permits.fs`.