Generating portal images

core.generate_image is a utility on the core object that renders a branded PNG for a Cloudpath tenant-property portal or management portal. It runs a small image pipeline inside the Worker and hands the PNG bytes back to your code as base64, so you can upload them through core.call in the same code_mode invocation — the bytes never round-trip the MCP transport.

Four targets, two upload paths

Each target maps 1:1 to a Cloudpath upload endpoint. Logos are 4:1 banners; favicons are square monogram tiles.

Target	Size	Uploads to
tenant_logo	1024×256	POST /properties/{guid}/uiConfiguration/logoFile
tenant_favicon	128×128	POST /properties/{guid}/uiConfiguration/favicon
mgmt_logo	1024×256	POST /mgmtPortals/{guid}/uiConfiguration/logoFile
mgmt_favicon	128×128	POST /mgmtPortals/{guid}/uiConfiguration/favicon

Logos combine an AI-generated background (Workers AI, @cf/black-forest-labs/flux-1-schnell) with a typography overlay. Favicons skip the AI step entirely and render a pure monogram tile.

Parameters

Parameter	Required for	Notes
target	all	One of the four targets above
primaryText	logo targets	The main line of text
backgroundPrompt	logo targets	Subject and mood for the AI background
monogram	favicon targets	1–2 characters
primaryColor	all	Hex, e.g. #0D2B45
accentColor	all	Hex
secondaryText	optional	Second line on logos
textColor	optional	Hex, default #FFFFFF
font	optional	inter (default), playfair, montserrat, dm-serif
layout	optional	left-gradient, center-vignette, bottom-bar (defaults: left-gradient for logos, center-vignette for favicons)

Tip

For logo targets, a banner-composition aspect hint is auto-prepended to your backgroundPrompt so the AI output survives the 4:1 cover-crop. Focus your prompt on subject and mood — the aspect guidance is handled for you.

Return shape

{ imageBase64, mimeType, width, height, suggestedFilename, model, aiGenerationMs, overlayMs }

model is the Workers AI model used, or null for favicons (which make no AI call). suggestedFilename is the value to use in the multipart upload’s text field — see below.

Uploading the image

The four uiConfiguration upload endpoints expect multipart/form-data, and uploading them has two gotchas that will silently corrupt the result if missed:

Danger

The text field that names the stored file is filename for logoFile endpoints and iconFilename for favicon endpoints. Cloudpath reads that form field — not the Content-Disposition: filename= attribute. A wrong or missing field name returns 200 OK and silently clears the stored image.

Second, because the isolate marshals tool arguments through JSON.stringify, you cannot pass a Uint8Array, FormData, or Blob as body — assemble the multipart body yourself, base64-encode it, and pass it as bodyBase64 with the Content-Type (including the boundary) set in headers. See Calling conventions.

// Generate + upload a property portal logo in a single code_mode call.
async () => {
  const img = await core.generate_image({
    target: 'tenant_logo',
    primaryText: 'HARBORVIEW RESIDENCES',
    backgroundPrompt: 'aerial view of a luxury waterfront community at golden hour',
    primaryColor: '#0D2B45',
    accentColor: '#C8960C',
    font: 'playfair',
  });

  // Decode the returned PNG bytes.
  const bin = atob(img.imageBase64);
  const png = new Uint8Array(bin.length);
  for (let i = 0; i < bin.length; i++) png[i] = bin.charCodeAt(i);

  // Build the multipart body: a `filename` text part + the `file` image part.
  const boundary = '----cp-mcp-' + Math.random().toString(36).slice(2);
  const enc = new TextEncoder();
  const head = enc.encode(
    `--${boundary}\r\nContent-Disposition: form-data; name="filename"\r\n\r\n${img.suggestedFilename}\r\n` +
    `--${boundary}\r\nContent-Disposition: form-data; name="file"; filename="${img.suggestedFilename}"\r\nContent-Type: image/png\r\n\r\n`
  );
  const tail = enc.encode(`\r\n--${boundary}--\r\n`);
  const body = new Uint8Array(head.length + png.length + tail.length);
  body.set(head, 0);
  body.set(png, head.length);
  body.set(tail, head.length + png.length);

  // Base64-encode in chunks (spread would overflow the call stack), one btoa at the end.
  let s = '';
  for (let i = 0; i < body.length; i += 0x8000) {
    const sub = body.subarray(i, i + 0x8000);
    for (let j = 0; j < sub.length; j++) s += String.fromCharCode(sub[j]);
  }

  const r = await core.call({
    method: 'POST',
    path: '/properties/{guid}/uiConfiguration/logoFile',
    pathParams: { guid: 'your-property-guid' },
    headers: { 'Content-Type': `multipart/form-data; boundary=${boundary}` },
    bodyBase64: btoa(s),
  });
  return { uploaded: r.ok, status: r.status, model: img.model };
}

Note

Image generation uses paid Workers AI compute for logo targets (favicons do not). If you only need a favicon, its target makes no AI call.