Metadata

name: build-pixel-pet-sprites
description: Create a production-ready chibi pixel-art virtual desktop pet based on a character reference image, including character design sheets, multi-action animation sprite sheets, transparent RGBA frame assets, action strips, asset inventories, GIF previews, automatic character alignment using alpha edges and connected-component analysis, jitter measurement, asset validation, ZIP packaging, and web integration delivery. Use this for creating virtual desktop pets, pixel mascots, animated sprites, frame-by-frame animations, character animation alignment, or fixing position drift between animation frames.

Build Pixel Pet Sprites

Create a reusable, aligned sprite package from a character reference or repair an existing package whose subject drifts between frames.

Route the task

For a new character/reference, run the complete workflow.
For new actions on an existing pet, reuse the approved character master and the same dedicated image-generation subagent.
For an existing transparent package with visible drift, skip generation and start at alignment.
For web integration only, use the aligned atlas and sprite-manifest.json; do not request new images.

Complete workflow

1. Define the animation specification

Collect:

reference image paths and their roles;
character invariants that must never drift;
ordered action names;
exact frame count, duration, and loop behavior for each action;
target frame dimensions and final output directory;
transparent output, preview, and web-delivery requirements.

Choose one row per action and chronological frames from left to right. Prefer equal frame counts when the consuming application benefits from a rectangular atlas.

2. Generate through the imagegen skill

Read and follow the installed imagegen skill. Use its dedicated-subagent workflow so the main thread receives no image bytes or Base64.

Generate in this order:

a full-body character master that locks identity, costume, palette, proportions, and pixel density;
an animation atlas using the approved master as a strict reference.

Pass local references with referenced_image_paths. Keep later revisions with the same generating subagent. Use the prompt patterns in references/prompting.md.

For transparent assets, generate on uniform #FF00FF, then use the imagegen skill's installed remove_chroma_key.py helper. Do not modify scripts/image_gen.py.

3. Build the deterministic package

Create a package configuration using references/package-config.md, then run:

python scripts/build_sprite_package.py <transparent-atlas.png> <config.json> <output-dir> --character-master <master.png>

The script normalizes the atlas with nearest-neighbor sampling and produces the atlas, action strips, individual frames, previews, manifest, and ZIP.

4. Align the subject before delivery

Always align generated animation frames, even when visual inspection looks acceptable:

python scripts/align_sprite_frames.py <package-dir> <aligned-output-dir>

The aligner:

thresholds the Alpha channel;
applies morphological closing;
selects a central, body-like connected component with lower-frame presence;
excludes detached effects from anchor detection;
derives a body/support anchor and a per-action median target;
translates the complete RGBA frame with integer offsets only;
records offsets and before/after jitter without scaling or blurring pixels.

If the complete content cannot move without clipping, regenerate or package with more transparent padding. Do not silently crop the main subject.

5. Validate the aligned package

Run:

python scripts/validate_sprite_package.py <aligned-output-dir>

Require all checks to pass:

expected actions and exact frame counts;
consistent RGBA dimensions;
non-empty frames and correct strip/atlas sizes;
transparent corners and zero outer-edge contamination;
no clipped main subject;
materially reduced within-action X/Y anchor jitter.

Inspect generated visual content only in the generating subagent. Use script reports for dimensions, alpha, edges, anchors, and jitter.

6. Deliver

Return:

aligned output directory and ZIP;
aligned atlas and manifest;
preview GIF path;
final prompt set and generation mode for generated work;
brief QA with frame totals, dimensions, issues, and before/after jitter.

Keep the unaligned source package. Never overwrite existing assets; create a versioned sibling. Do not return Base64, discarded variants, or high-volume image tool output.

Web handoff

Recommend loading one atlas plus sprite-manifest.json rather than requesting every frame separately. Render the atlas with Canvas or CSS background positioning, disable image smoothing, and use the manifest's duration, loop, row, dimensions, and anchor data.

build-pixel-pet-sprites

安装技能