PNG export

Export from the command line

heze notes.md --export notes.png --width 1200 --height 800 --theme light

--export writes a PNG instead of opening a preview. Export works without a graphical desktop and does not require --backend headless.

Use positive integer dimensions. The output is a fixed viewport, not a paginated or automatically fitted document; content below its height is outside the image. Increase the height or shorten the document when necessary.

An existing output file is overwritten. Create the destination directory before exporting there. When the input is a directory, Heze exports its first sorted Markdown file without the browser sidebar; pass a specific file to choose another document.

The renderer produces repeatable bytes for the same input, dimensions, theme, and rendering environment. Fonts and installed dependency versions can affect results across machines.

Refresh an export on save

heze notes.md --export notes.png --width 1200 --height 800 --watch

Heze creates the initial PNG, then overwrites it when the Markdown file changes. It prints heze: updated notes.md after a successful refresh. Press Ctrl+C to stop. Watching a directory tracks only its first sorted Markdown file.

Use a one-time export for SVG files; the current reload path parses changes as Markdown.

Render from Ruby

Save this as export.rb and run ruby export.rb:

require "heze"

document = Heze::Markdown.parse("# Hello\n\nRendered by Heze.")
renderer = Heze::Renderer.new(
  theme: Heze::Theme.resolve(:light),
  width: 1200,
  height: 630
)
File.binwrite("preview.png", renderer.render(document))

render returns PNG bytes. Without options, Heze::Renderer.new uses the dark theme and a 900 × 1000 viewport, matching the CLI defaults.

To read a source file through Heze’s encoding detection and supply its directory for local image paths:

path = File.expand_path("notes.md")
document = Heze::Markdown.parse(Heze::Source.read(path))
png = renderer.render(document, base_path: File.dirname(path))
File.binwrite("notes.png", png)

The same Markdown rendering limits apply to the Ruby API. Continue with SVG files, or return to previewing documents.