# `Etcher.Raster`
[🔗](https://github.com/alexdont/etcher/blob/v0.9.0/lib/etcher/raster.ex#L1)
Server-side, dependency-free rendering of Etcher annotations to static output.
Etcher renders shapes live (SVG) on the Fresco canvas in the browser. This
module is the *server* counterpart: it turns the same annotation geometry into
either **ImageMagick `convert -draw` arguments** (to bake shapes into a raster
— e.g. an annotated thumbnail) or a standalone **SVG string** (to overlay
shapes on an image without JS).
It is the single source of truth for "Etcher geometry → drawn shape" on the
server, mirroring the wire format documented in the README. Pure functions, no
system dependencies — the caller owns rasterization (running `convert`,
embedding the SVG, …).
## Input
A list of annotation maps as they travel in `etcher:annotations-changed` /
the `extensions.etcher` blob — `%{"kind" => ..., "geometry" => ..., "style" =>
...}` (string keys; atom keys are also accepted). Unknown or malformed shapes
are skipped, so one bad row never breaks a render.
## Examples
iex> rect = [%{"kind" => "rectangle", "geometry" => %{"x" => 10, "y" => 20, "w" => 30, "h" => 40}}]
iex> Etcher.Raster.to_draw_args(rect, stroke_width: 4)
["-fill", "none", "-stroke", "#ef4444", "-strokewidth", "4", "-draw", "rectangle 10,20 40,60"]
iex> rect = [%{"kind" => "rectangle", "geometry" => %{"x" => 10, "y" => 20, "w" => 30, "h" => 40}}]
iex> Etcher.Raster.to_svg(rect, width: 100, height: 100)
~s()
# `annotation`
```elixir
@type annotation() :: map()
```
# `opts`
```elixir
@type opts() :: keyword()
```
# `primitives`
```elixir
@spec primitives([annotation()]) :: [{tuple(), String.t() | nil}]
```
Normalises annotations into drawing primitives + colour.
Each entry is `{primitive, color}` where `primitive` is one of:
`{:rect, x, y, w, h}`, `{:circle, cx, cy, r}`, `{:polygon, points}`,
`{:polyline, points}`, `{:line, x1, y1, x2, y2}` (coords are numbers, `points`
is a list of `{x, y}`). Exposed so callers can add their own backend.
# `to_draw_args`
```elixir
@spec to_draw_args([annotation()], opts()) :: [String.t()]
```
Builds ImageMagick `convert` arguments that draw the annotations' outlines.
Returns a flat arg list to splice into a `convert` invocation *before* any
resize/crop, so shapes are drawn in the source image's pixel space (Etcher
geometry is in canvas/image pixels) and scale with the image.
Returns `[]` when there is nothing drawable.
## Options
* `:stroke_width` — outline width in source pixels (default `2`)
* `:default_color` — colour for shapes without a `style` colour (default `#ef4444`)
# `to_svg`
```elixir
@spec to_svg([annotation()], opts()) :: String.t()
```
Renders the annotations as a standalone `