FontData: blob() method
Experimental: This is an experimental technology
Check the Browser compatibility table carefully before using this in production.
The blob()
method of the FontData
interface returns a Promise
that fulfills with a Blob
containing the raw bytes of the underlying font file.
Syntax
js
blob()
Parameters
None.
Return value
Examples
The blob()
method provides access to low-level SFNT data — this is a font file format that can contain other font formats, such as PostScript, TrueType, OpenType, or Web Open Font Format (WOFF).
js
async function computeOutlineFormat() {
try {
const availableFonts = await window.queryLocalFonts({
postscriptNames: ["ComicSansMS"],
});
for (const fontData of availableFonts) {
// `blob()` returns a Blob containing valid and complete
// SFNT-wrapped font data.
const sfnt = await fontData.blob();
// Slice out only the bytes we need: the first 4 bytes are the SFNT
// version info.
// Spec: https://docs.microsoft.com/en-us/typography/opentype/spec/otff#organization-of-an-opentype-font
const sfntVersion = await sfnt.slice(0, 4).text();
let outlineFormat = "UNKNOWN";
switch (sfntVersion) {
case "\x00\x01\x00\x00":
case "true":
case "typ1":
outlineFormat = "truetype";
break;
case "OTTO":
outlineFormat = "cff";
break;
}
console.log("Outline format:", outlineFormat);
}
} catch (err) {
console.error(err.name, err.message);
}
}
Specifications
Specification |
---|
Local Font Access # ref-for-dom-fontdata-blob① |
Browser compatibility
BCD tables only load in the browser