Image production

Hydracept returns assets ready for your workflow.

Search terms teams actually use: sprite sheet AI, transparent PNG generation, pixel art animation frames, inventory icon packs, contact sheet slice, chroma key matte for games.

For image.generate.v1, that means transparent PNGs, cohesive multi-asset sheets, variant sets, and centered frames you can use in Unity, Godot, Unreal, or a web pipeline.

Three production modes

Best for sprite sheets, pixel art animation, character poses, inventory icons, item families, VFX frames, prop packs, and UI glyphs — small-format assets where intra-set cohesion matters more than hero-resolution detail.

Sheet & Slice

Describe a cohesive set once. Hydracept generates a single composition, mattes the chroma plate, grid-slices (with blob fallback if the layout is skewed), centers each cell, and returns individual artifacts.

sheet.labels are metadata only — they identify cells in the API response and never appear in the provider prompt or on the generated image.

Example: SNES knight sword-swing sheet (gpt-image-2), matte-processed — hover the homepage demo to compare chroma vs transparency.

Aligned GIF preview built from sliced transparent frames of the same job.

Request

{
  "context": {
    "productId": "my-game",
    "projectId": "cpr_...",
    "environment": "development"
  },
  "input": {
    "prompt": "SNES-era pixel art knight sword swing animation",
    "requestTransparentOutput": true,
    "sheet": {
      "rows": 4,
      "columns": 4,
      "slice": true,
      "animation": { "facing": "right" },
      "labels": [
        "frame-01", "frame-02", "frame-03", "frame-04",
        "frame-05", "frame-06", "frame-07", "frame-08",
        "frame-09", "frame-10", "frame-11", "frame-12",
        "frame-13", "frame-14", "frame-15", "frame-16"
      ],
      "normalize": {
        "width": 256,
        "height": 256,
        "center": true
      }
    }
  },
  "execution": { "executionPreference": "automatic" },
  "idempotencyKey": "sword-swing-sheet-1"
}

Submit as a durable job:

POST /v1/capabilities/image.generate.v1/jobs
Authorization: Bearer <HYDRACEPT_API_KEY>
Content-Type: application/json

Behavior

• sheet.labels optionally name each cell in the API response (frame-01, slash-b, etc.). They are not sent to the provider and must not be drawn on the image. Succeeded jobs expose every cell on GET /v1/jobs/{jobId} as its own artifact with label, filename, and sliceCellId.
• sheet.animation requests subtle frame-to-frame motion with a locked facing direction.
• sheet.slice must be true to activate slicing.
• sheet.normalize sets the output canvas per cell (width, height, center). center trims and centers each grid cell; it does not switch the slicer to blob detection.
• variantCount must be 1 when sheet slicing is enabled.
• Hydracept uses provider-native transparency when available and matte normalization when needed.

Output

A succeeded job returns multiple artifacts — one per sliced cell — on the job resource. Download each with:

GET /v1/jobs/{jobId}/artifacts/{artifactId}

Transparent output

For a single asset:

{
  "input": {
    "prompt": "pixel art healing potion icon, isolated",
    "requestTransparentOutput": true
  }
}

Hydracept treats transparency as an output contract. The catalog model record decides the default path:

• Native alpha when nativeTransparentBackground is true (gpt-image-2, gpt-image-1, and later gpt-image-2.x models). Hydracept sends background: "transparent" and does not chroma-key or run matte v9. A client transparencyMethod of matte-v9 is ignored on these models.
• Chroma-key matte only when the model has no native alpha.

Optional keyColor and transparentRegions apply only to the matte path.

Optional transparentRegions selects which pixels go to alpha when requestTransparentOutput is true:

{
  "input": {
    "prompt": "full-bleed interior, window openings punched",
    "requestTransparentOutput": true,
    "transparentRegions": "borderConnectedAndEnclosed",
    "keyColor": "#00ffff"
  }
}

Opaque jobs (requestTransparentOutput: false) fill the canvas. Clients should not re-key the returned PNG.

Verify transparency from bytes, not previews

Image viewers, chat clients, IDE previews, and vision tools may composite a transparent PNG onto a black or white matte. That matte is a viewer choice; it is not background color stored in the PNG. Do not judge Hydracept PNG transparency from a thumbnail, generic image Read, or vision description.

Smoke validation now returns both transparencyOk and a structured transparencyReport. A passing report includes decoded alpha and isolation evidence such as hasAlphaChannel, transparentPixelRatio, opaqueCornerCount, and chromaPlateRatio, plus verdict: "valid_transparent_sprite".

For a downloaded artifact, inspect the file bytes directly:

python -m hydracept verify .hydracept/demo/first-asset.png --json

Example shape:

{
  "schemaVersion": "hydracept.cli.png-transparency.v1",
  "kind": "png_transparency",
  "passed": true,
  "transparencyOk": true,
  "transparencyReport": {
    "schemaVersion": "hydracept.png-transparency.v1",
    "verdict": "valid_transparent_sprite",
    "hasAlphaChannel": true,
    "transparentPixelRatio": 0.7883,
    "opaqueCornerCount": 0,
    "chromaPlateRatio": 0.0
  }
}

The inspector verdict is authoritative. Do not substitute a shortcut based only on transparent-pixel ratio or corner count: Hydracept also checks for connected leftover chroma plate and other invalid alpha states. A passing report should not be overridden merely because a host preview appears black or white.

When MCP Apps are available, prefer hydracept_interaction_surface with artifact.review for human visual review. The Hydracept review surface presents transparent assets appropriately; use it to judge composition and aesthetics. Use transparencyReport / local byte verification to judge alpha correctness.

Variants

Ask for multiple creative takes in one job:

{
  "input": {
    "prompt": "rusted plasma wrench inventory icon",
    "variantCount": 4,
    "requestTransparentOutput": true
  }
}

Poll the job, compare artifacts, and keep the exact artifactId you want. Provenance stays on the job receipt.

When to use sheets vs variants

Sheets share one canvas, so they are ideal for sprites, icons, and other related asset sets.

Contract sources

• Capability input schema: GET /v1/capabilities/image.generate.v1 and agent context
• Job lifecycle: Durable Jobs & Receipts
• Public OpenAPI: https://hydracept.com/openapi/hydracept-v1.json