sheetjs/js-wmf

Windows MetaFile (wmf) processor

js-wmf

Processor for Windows MetaFile (WMF) files in JS (for the browser and nodejs).

Installation

With npm:

$ npm install wmf

In the browser:

<script src="wmf.js"></script>

The browser exposes a variable WMF.

Usage

The data argument is expected to be an ArrayBuffer, Uint8Array or Buffer

• WMF.image_size(data) extracts the image offset and extents, returns an Array [width, height] where both metrics are measured in pixels.

• WMF.draw_canvas(data, canvas) parses the WMF and draws to a Canvas.

Notes

• The library assumes the global ImageData is available. For nodejs-powered canvas implementations, a shim must be exposed as a global. Using the canvas npm package:

const { createImageData } = require("canvas");
global.ImageData = createImageData;

• OffscreenCanvas in Chrome and some other Canvas implementations require the dimensions in the constructor:

const size = WMF.image_size(data);
const canvas = new OffscreenCanvas(size[0], size[1]);

Examples

Browser Fetch into canvas (click to show)

// assume `canvas` is a DOM element
(async() => {
  const res = await fetch("url/for/image.wmf");
  const ab = await res.arrayBuffer();
  WMF.draw_canvas(ab, document.getElementById("canvas"));
})();

NodeJS (using `canvas` npm module) (click to show)

const { createCanvas, createImageData } = require("canvas");
global.ImageData = createImageData;

const size = WMF.image_size(data);
const canvas = createCanvas(size[0], size[1]);
WMF.draw_canvas(data, canvas);

License

Please consult the attached LICENSE file for details. All rights not explicitly granted by the Apache 2.0 License are reserved by the Original Author.

References

• MS-WMF: Windows Metafile Format

js-wmf's Issues

Support WMF files that start with META_PLACEABLE record

Hi there, according to MS-WMF 2.3.2.3, it seems that WMF files may start with a META_PLACEABLE record before the META_HEADER record. These files currently give a "Header: Type 52695 must be 1 or 2" error with js-wmf.

I think these files could be supported by updating image_size_prepped_bytes() to check for files that start with the META_PLACEABLE signature of 0x9AC6CDD7, and then skipping ahead 22 bytes to get to the actual META_HEADER record.

As for sample files, it looks like most of the "iPres Systems Showcase" WMF files are of this "placeable" variant.

I'm happy to work on a PR if you would like.

Error: the string "Header: Type 52695 must be 1 or 2" was thrown, throw an Error :)

The sample file: BIRD.WMF.zip

The sample code:

var jsEnv = require("browser-or-node");
var canvas = require("canvas");
// eslint-disable-next-line no-undef
global.ImageData = canvas.createImageData;

var data = fs.readFileSync(path.join(__dirname, 'test-data', 'BIRD.WMF'));
var WMF;
if (jsEnv.isNode) {
    WMF = require('wmf/dist/wmf.node');
} else {
    WMF = require('wmf/dist/wmf');
}
console.log(typeof data);
var size = WMF.image_size(data);
console.log(size);