# Poster Tiler (Big Picture on Many Pages)

> Print a big poster on ordinary paper: tiles with overlap, crop marks and an assembly map. Enlarge a JPEG or PNG to a poster of any width and split it over A4, Letter or other sheets with overlap, trim lines, crop marks, alignment crosses and tile names, plus a cover page with the assembly map, the effective resolution and a test square. Without an image you get the tiling plan.

Part of usefulweb.app (https://usefulweb.app/). Part of [Printshop](https://printshop.usefulweb.app/) (ownerApp: printshop). Results are deterministic calculations from the inputs and the listed assumptions; the API returns exactly what the web page shows.

## Use it
- Human interface: https://printshoppostertiler.usefulweb.app/ (interactive tool at https://printshoppostertiler.usefulweb.app/tool)
- JSON API: POST https://printshoppostertiler.usefulweb.app/api/v1/calculate with a JSON object of inputs (schema: https://printshoppostertiler.usefulweb.app/api/v1/tool)
- OpenAPI: https://printshoppostertiler.usefulweb.app/openapi.json
- MCP (Streamable HTTP): https://printshoppostertiler.usefulweb.app/mcp - tool `printshop_poster_tiler`

## Inputs
- image (file): Image (JPEG or PNG, optional)
- imageWidth (integer): Image width in pixels (when no file)
- imageHeight (integer): Image height in pixels (when no file)
- width (number): Poster width (mm)
- paper (select): Paper size
- orientation (select): Sheet orientation
- margin (number): Printer margin (mm) - Most printers cannot print the outer 3–6 mm.
- overlap (number): Overlap (mm)
- cropMarks (boolean): Crop marks and alignment crosses
- title (text): Title on the cover page

## Method
- Printable area = paper − 2 × margin; each next sheet starts one step = printable − overlap further, so neighbouring sheets share the overlap strip. Sheets across = ceil((poster − overlap) / step); with “fewest sheets” both orientations are tried.
- The image is embedded once (JPEG unchanged, PNG losslessly compressed) and every sheet shows its part through a clipping rectangle, so the PDF stays small and keeps the full resolution.
- Effective resolution = image pixels ÷ poster inches (Lumina’s print planner gives the matching print size table). Below about 100 pixels per inch prints look soft up close.

## Limits
- Printers differ slightly in scale and margins: print the cover page first and measure the 50 mm test square. Interlaced PNG and CMYK JPEG files are not supported.