assetgen

Assetgenfile Format Documentation

File Structure

• Global Directives All global settings (everything except ASSET) must appear before any ASSET entries.
• Order Sensitivity
  • You may include multiple PROMPT lines; each line will be concatenated in order to form the full prompt.
  • All other global directives (MODEL, SIZE, etc.) may appear only once.
• Asset Directives All ASSET lines must come after every global directive. Each one defines a filename and its specific prompt.

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Default Behaviors & Requirements

• Required Directives
  • At least one ASSET line is mandatory.
  • PROMPT lines are optional but strongly recommended—they establish shared context for all assets and help ensure reproducible results.
• Syntax Validation
  • Any directive not listed in this documentation will trigger a syntax error and abort processing.

• Global Directive Defaults If a global directive is omitted, it is simply not sent to the OpenAI API, and the API’s own default behavior applies. CLI defaults (when you do set them) are:

  Directive	Default Value	Notes
  MODEL	dall-e-2
  SIZE	(API default)	DALL·E-2: 256x256 gpt-image-1: auto
  BACKGROUND	auto	(gpt-image-1 only)
  MODERATION	auto	(gpt-image-1 only)
  OUTPUT_COMPRESSION	100	(gpt-image-1 only; applies to JPEG/WEBP)
  QUALITY	(API default)	gpt-image-1: auto dall-e-3: hd dall-e-2: standard
  STYLE	vivid	(dall-e-3 only)

• Reproducibility Best Practice Where possible, explicitly specify each directive in your spec file so that future API-default changes won’t alter your generated assets.

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Asset-Specific Overrides

• ASSET Directives Each asset is declared with an ASSET line in the form:

  ASSET <filename> <asset-specific prompt>
  

• Prompt Composition
  • The effective prompt sent to the API is the concatenation of all global PROMPT lines (in order) followed by the asset-specific prompt text.
• Filename Guidelines
  • Filenames must not contain any whitespace characters.
  • The file extension (e.g. .png, .jpeg, .webp) is used to auto-detect the output format.
• Error Handling
  • Any ASSET line without a valid filename or prompt will trigger a syntax error.
  • Any filename containing whitespace or an unsupported extension will trigger a validation error.

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Directive Details

MODEL

Choose which OpenAI image-generation model to use.

• Valid Values: dall-e-2, dall-e-3, gpt-image-1
• Recommendations:
  • gpt-image-1 for highest quality (most expensive)
  • dall-e-3 for strong balance of quality & cost
  • dall-e-2 for basic assets or cost-sensitive needs
• Model-Specific Constraints:
  • Size
    • DALL·E-2: 256x256, 512x512, 1024x1024
    • DALL·E-3: 1024x1024, 1792x1024, 1024x1792
    • GPT-Image-1: 1024x1024, 1536x1024, 1024x1536, auto
  • Quality
    • DALL·E-2: standard
    • DALL·E-3: hd, standard
    • GPT-Image-1: auto, high, medium, low
  • Style: only for DALL·E-3 (vivid, natural)
  • Background/Moderation/Compression: only for GPT-Image-1

SIZE

Specifies image dimensions (maps to the API’s size parameter).

• Valid Values (by model):
  • DALL·E-2: 256x256, 512x512, 1024x1024
  • DALL·E-3: 1024x1024, 1792x1024, 1024x1792
  • GPT-Image-1: 1024x1024, 1536x1024, 1024x1536, auto
• Notes:
  • Omitted → API default (256x256 for DALL·E-2)
  • auto (GPT-Image-1) lets the API choose

BACKGROUND

Controls transparency (GPT-Image-1 only).

• Valid Values: transparent, opaque, auto
• Notes:
  • Omitted → auto
  • Use transparent for compositing, opaque for full scenes

MODERATION

Sets content moderation level (GPT-Image-1 only).

• Valid Values: low, auto
• Notes:
  • Omitted → auto
  • low for benign game assets, auto for general safety

OUTPUT_COMPRESSION

JPEG/WEBP compression level (GPT-Image-1 only).

• Valid Values: 0–100
• Notes:
  • Omitted → 100
  • Lower → smaller size, lower fidelity

QUALITY

Rendering fidelity.

• Valid Values:
  • DALL·E-2: standard
  • DALL·E-3: hd, standard
  • GPT-Image-1: auto, high, medium, low
• Notes:
  • Omitted → API default
  • Higher → better detail, higher cost

STYLE

Stylistic bias (DALL·E-3 only).

• Valid Values: vivid, natural
• Notes:
  • Omitted → vivid
  • vivid for cartoons, natural for realism

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Example Spec

PROMPT A clean top-down 2-D sprite on a transparent background.
PROMPT Include subtle shadows for depth.
MODEL gpt-image-1
SIZE 1024x1024
BACKGROUND transparent
MODERATION low
OUTPUT_COMPRESSION 80
QUALITY high

ASSET road_straight_ns.png A seamless 256×256 asphalt road segment running north–south.
ASSET tree.png A stylized pine tree with dark green needles.
ASSET icon.webp A glowing energy orb with electric sparks.

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