File size increased hugely after embeded font through fontkit

[Pomelool]

I have a pdf that is 600KB, after embeded a font (ttf file of 20MB), and drawed one line with this font, my generated pdf becomes 9mb. Is this a normal behavior? Or am I doing something wrong?

Is there a way to subsetting a font instead of embedding the whole font?

[Hopding]

Hello @Pomelool! This is normal. pdf-lib does not subset embedded fonts by default. Instead, it embeds the entire font into the document. However, there is an option to use subsetting when you embed the font. It is an option you must pass to PDFDocument.embedFont. For example:

const ubuntuBytes = ...
const ubuntuFont = await pdfDoc.embedFont(ubuntuBytes, { subset: true })

And here are some other examples:

pdf-lib/apps/node/tests/test1.ts

Lines 168 to 228 in 7e06c40

	const ubuntuFont = await pdfDoc.embedFont(fonts.ttf.ubuntu_r_base64, {
	subset: true,
	});
	page2.drawText(ipsumLines.join('\n'), {
	y: size - 20,
	size: 20,
	font: ubuntuFont,
	lineHeight: 20,
	});
	const fantasqueFont = await pdfDoc.embedFont(
	fonts.otf.fantasque_sans_mono_bi,
	);
	page2.drawText(ipsumLines.join('\n'), {
	y: size - 105,
	size: 25,
	font: fantasqueFont,
	lineHeight: 25,
	});
	const indieFlowerFont = await pdfDoc.embedFont(fonts.ttf.indie_flower_r, {
	subset: true,
	});
	page2.drawText(ipsumLines.join('\n'), {
	y: size - 200,
	size: 25,
	font: indieFlowerFont,
	lineHeight: 25,
	});
	const greatVibesFont = await pdfDoc.embedFont(fonts.ttf.great_vibes_r, {
	subset: true,
	});
	page2.drawText(ipsumLines.join('\n'), {
	y: size - 300,
	size: 30,
	font: greatVibesFont,
	lineHeight: 30,
	});
	const appleStormFont = await pdfDoc.embedFont(fonts.otf.apple_storm_r);
	page2.drawText(ipsumLines.join('\n'), {
	y: size - 425,
	size: 25,
	font: appleStormFont,
	lineHeight: 25,
	});
	const bioRhymeFont = await pdfDoc.embedFont(fonts.ttf.bio_rhyme_r, {
	subset: true,
	});
	page2.drawText(ipsumLines.join('\n'), {
	y: size - 500,
	size: 15,
	font: bioRhymeFont,
	lineHeight: 15,
	});
	const pressStart2PFont = await pdfDoc.embedFont(fonts.ttf.press_start_2p_r, {
	subset: true,
	});

It's important to note that subsetting does not work for all fonts. This is why the feature is not enabled by default. The subsetting logic resides in the @pdf-lib/fontkit module, which is a fork of https://github.com/foliojs/fontkit. If the subsetting bug in fontkit is ever fixed, then I can pull it into pdf-lib and perhaps enable subsetting by default.

I hope this helps. Please let me know if you have any additional questions!

[vlio20]

Thanks @Hopding . I suggest that you will add this to your documentation in the README.md file

[Hopding]

That's a good idea. It would make a nice addition to the https://github.com/Hopding/pdf-lib#fonts-and-unicode section. Happy to accept PRs for this!

[vlio20]

Sure I will happy to that!

[vlio20]

@Hopding , another question if I may. Is it possible to embed multiple fonts (to increase the chance of successful conversion)?