Images that belong to their row

An avatar column that points at picsum.photos is a placeholder twice over: it needs the network, and it depicts nobody. Synth draws the picture instead, from the row's own text.

type User struct {
    ID     uuid.UUID `synth:"pk"`
    Name   string
    Avatar string `synth:"avatar,from=Name"`      // initials, colour, shape from the name
    Icon   string `synth:"identicon,from=ID"`     // the GitHub-style pixel mark
}

Four kinds: avatar (a person), productimage (a catalogue thumbnail), logo (a company monogram), identicon (a symmetric mark for any key).

The image is a pure function of the subject, so the same person keeps the same face across runs, across formats and across datasets — regenerate the fixture and the diff is empty. from= is what ties it to the row; without it the picture depicts an unrelated name.

Parameters

Param	Meaning
from=<field>	take the subject from a sibling column
format=	dataurl (default, base64 SVG), svg, png
size=	edge length in pixels (default 128, max 1024)
dir=	write files there, put the path in the column
seed=	a different but equally stable image
vary=true	let repeated subjects differ (off by default)

No network, no fonts

Nothing is fetched and no font is required: text is rasterized from a built-in 5×7 bitmap into plain rectangles, so the SVG renders identically everywhere and matches the PNG exactly. The renderer is usable on its own as imagegen, and the dataurl default drops straight into a browser with no file to ship alongside it.

Worked example: examples/images, examples/catalog.yaml.

The imageurl kind is unchanged — it still returns a placeholder-service URL for cases that want one.