Sam Howard Sam is a developer at IDRsolutions who specialises in font rendering and conversion. He's also enjoyed working with SVG, Java 3D, Java FX and Swing.

Why the TrueType hinting patent expiration matters

1 min read

A while back we put a lot of effort into implementing some of the hinting technology in the TrueType specification. This system effectively uses small programs in a stack based environment to manipulate the set of points which define the contours of a glyph.

Up until recently, some of the instructions available in the language were covered by a set of patents belonging to Apple, meaning anyone wishing to actually execute those particular instructions would need a licence from Apple. Unfortunately the patented instructions were the most frequently used instructions for moving points, meaning that simply executing the rest of the instructions does more harm than good. Now that those patents have expired, this is no longer an issue.

So what does this actually mean? These patents have stood for 20 years and the world hasn’t fallen apart.

Well, that’s true. New font technologies have been developed with different hinting mechanisms, tools for rendering TrueType have created their own automatic hinting algorithms and antialiasing technologies have vastly improved. All of this is true, and to some extent has reduced the need for the original hinting instructions, but the fact remains that a font hand hinted by an expert will always look clearer than any automatically hinted rendering.

However, what really clinches it for me is the fact that numerous Chinese fonts actually construct their glyphs by defining a range of glyphs as simple strokes, then using them in composite glyphs which are heavily manipulated by hinting instructions in order to form the final characters. It is impossible to work around as performing the relevant shifts and alignments uses the methods described by the patents. Now that the patents have expired there will be no need to buy a license from Apple, meaning many products can now add (or enable) the functionality used to display these fonts, including open source packages like FreeType which is used for font rendering in many Linux distributions.

Individual stroke component glyphs

Unhinted composite glyph outline

Final hinted glyph

There’s a lot of discussion on this topic over at Slashdot, and some more details about what was patented can be found at the home of FreeType.

This post is part of our “Understanding the PDF File Format” series. In each article, we discuss a PDF feature, bug, gotcha or tip. If you wish to learn more about PDF, we have 13 years worth of PDF knowledge and tips, so click here to visit our series index!

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Sam Howard Sam is a developer at IDRsolutions who specialises in font rendering and conversion. He's also enjoyed working with SVG, Java 3D, Java FX and Swing.

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