`chart://`¶

Producer-only chart renderer wrapping go-analyze/charts, a pure-Go ECharts-style chart library. Turns a structured payload into a PNG / SVG / JPG / base64 image. Supports line, bar, horizontal-bar, pie, doughnut, candlestick (OHLC), radar, funnel, heatmap, scatter, violin, and stacked variants. Also accepts raw ECharts JSON option objects for full-fidelity ECharts rendering.

Producer-only — CreateConsumer returns ErrConsumerNotSupported.

URI shape¶

chart://<name>?type=line&width=800&height=400&format=png&theme=light

Parameters¶

Param	Type	Default	Description
`type`	enum	`line`	`line`, `bar`, `horizontal-bar`, `pie`, `doughnut`, `candlestick`, `radar`, `funnel`, `heatmap`, `scatter`, `violin`, `echarts` (raw ECharts option JSON).
`width`	integer	`800`	Output width (px for PNG/JPG; user units for SVG).
`height`	integer	`400`	Output height.
`format`	enum	`png`	`png`, `svg`, `jpg`/`jpeg`, `base64-png`/`base64-svg`/`base64-jpg`, `data-uri-png`/`data-uri-svg`/`data-uri-jpg`.
`theme`	enum	`light`	`light`, `dark`, `ant`, `vintage`, `westeros`, `wonderland`, `walden`, `natural`, `grafana`.
`title`	string	—	Chart title (overrides body.title).
`subtitle`	string	—	Subtitle.
`xLabel`, `yLabel`	string	—	Axis labels (override body fields).
`fontFamily`	enum	`notosans`	`notosans`, `notosans-bold`, `roboto`.
`showLegend`	boolean	`true`	Series legend.
`showSymbols`	boolean	`true`	Data-point markers (line / scatter).
`smoothLine`	boolean	`false`	Bezier smoothing for line charts.
`fillArea`	boolean	`false`	Fill area under line series.
`stack`	boolean	`false`	Stack series.
`horizontal`	boolean	`false`	Alias for `type=horizontal-bar`.
`candleStyle`	enum	`filled`	`filled` or `hollow` (candlestick body).
`candleWidth`	number	`0.8`	Candle body width ratio (0.0–1.0).
`padding`	integer	`10`	Chart padding (px).

Body shape¶

Per chart type:

Chart types	Expected body
`line`, `bar`, `horizontal-bar`, `pie`, `doughnut`, `radar`, `funnel`, `scatter`, `violin`	`{"values": [[...], [...]], "labels": [...], "series": ["A","B"], "title": "...", "xLabel": "...", "yLabel": "..."}` or `[][]float64` (multi-series) or `[]float64` (single-series).
`candlestick`	`{"ohlc": [[open, high, low, close], ...], "labels": [...]}`.
`echarts` (or `format=echarts-png\|echarts-svg\|echarts-jpg`)	A JSON string containing the full ECharts option object — rendered via `RenderEChartsToPNG` / `...SVG` / `...JPG`.

Headers¶

Written¶

Header	Description
`Content-Type`	`image/png`, `image/svg+xml`, `image/jpeg`, or `text/plain` (base64 / data-uri variants).
`chart.type`	Chart type.
`chart.format`	Output format.
`chart.width`, `chart.height`	Configured dimensions.
`chart.bytes`	Raw image size in bytes.

The body becomes the rendered image bytes (for native PNG / SVG / JPG), the base64 string (for base64-*), or the full data:image/...;base64,... URI (for data-uri-*).

Examples¶

Simple line chart:

- set-body:
    starlang: |
      %sl 2.0
      output application/json
      input payload
      ---
      {
        "values":  [[10, 25, 15, 40, 30]],
        "labels":  ["Mon","Tue","Wed","Thu","Fri"],
        "series":  ["Visitors"],
        "xLabel":  "Day",
        "yLabel":  "Count"
      }
- target: chart://visitors?type=line&width=900&height=400&theme=ant

Embed in an HTML report (data URI):

- set-body:
    starlang: |
      %sl 2.0
      output application/json
      input payload
      ---
      { "values": [[42, 38, 27]], "labels": ["A","B","C"] }
- target: chart://share?type=pie&format=data-uri-png
- transform:
    starlang: |
      %sl 2.0
      output text/html
      input payload
      ---
      "<img src=\"" ++ payload ++ "\"/>"

Candlestick from OHLC rows:

- set-body:
    starlang: |
      %sl 2.0
      output application/json
      input payload
      ---
      { "ohlc": payload.bars, "labels": payload.dates }
- target: chart://ohlc?type=candlestick&theme=dark&candleStyle=hollow

Raw ECharts option for advanced configurations:

- set-body:
    starlang: 'echarts_option_json(payload)'
- target: chart://custom?type=echarts&format=png

Behavior notes¶

Two-rail surface — the type=<simple> rail uses go-analyze/charts's high-level API (uniform across chart types). The echarts type drops to RenderECharts* for full ECharts compatibility.
Format and output coupling — format=base64-* returns a string body with Content-Type: text/plain. format=data-uri-* returns data:image/...;base64,... ready for an <img src>. Native formats keep image/... content types and raw bytes.
Padding default is intentionally small (10 px) — many themes draw axes / titles right up to the edge otherwise.
Theme set — chart themes match go-analyze/charts's named palettes; see the library's docs for the exact look.
Both Out() and In() are written. The In() body is overwritten so the next pipeline step sees the rendered chart, not the input data.

Source¶

pkg/component/chart/chart.go, pkg/component/chart/render.go

chart://¶