Placeholder Provider¶
Zero-cost solid-color PNG generation for testing, drafts, and CI pipelines.
Overview¶
The placeholder provider generates simple solid-color PNG images without any external dependencies or API keys. The color is selected from a palette of 6 predefined colors using a SHA-256 hash of the prompt as an index, so the same prompt always produces the same color.
When to use¶
- Testing -- verify your MCP client configuration without API costs
- Drafts and mock-ups -- create placeholder images during development
- CI pipelines -- test image generation workflows without external services
- Demos -- show the image generation flow without requiring API keys
Availability¶
The placeholder provider is always registered -- it requires no configuration, no API key, and no external service.
Aspect ratios¶
| Aspect ratio | Size |
|---|---|
1:1 |
256x256 |
16:9 |
640x360 |
9:16 |
360x640 |
3:2 |
480x320 |
2:3 |
320x480 |
Parameters¶
- prompt -- used to determine the output color (via SHA-256 hash index into a 6-color palette)
- negative_prompt -- ignored
- quality -- ignored
- aspect_ratio -- maps to pixel sizes above
- background --
"opaque"(default) produces RGB PNG;"transparent"produces RGBA PNG with alpha channel set to 0
Output¶
- Format: PNG (RGB for opaque, RGBA for transparent)
- Content: Solid color fill (fully transparent when
background="transparent") - Size: ~1-2 KB per image
- Generation time: Instant (< 1ms)