: Kerning on the fly Do anyone know any algorithm which would calculate automatically kerning of characters based on glyph shapes when user types text? I don't mean trivial calculation of advance

@Fox8063795

I know this is old. I'm working on this right now in a WebGL implementation of wobbly text (whatever). The solution I'm working on goes like this:


Get a bitmapped version of the glyph pair (or do it with vectors if you want)
For each row of pixels (or arbitrary vertical unit if you go with vectors), check that both glyphs have at least one pixel present
For each row that passes step 2, calculate the distance between the rightmost pixel of the first glyph and leftmost pixel of the second glyph
Move the second glyph as far left as it can go while still meeting these criteria:

the gap in that row of pixels is greater than some minimum gap you specified
the total area (ignoring rows with no pixel in one of the glyphs) is greater than some minimum area you specified



That way, the empty 'area' between letters should get squeezed to a pretty common average. Specify the minimum gap and the minimum area using trial and error and your own taste, and maybe allow those parameters to be adjusted by some other agent as well... like a manual kerning value.

yay :)

Edit: I've implimented this successfully now and it works really well :)

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@Kristi927

Algorithms for auto-kerning exist already. None are fool-proof and they tend to need a bit of hand-holding and manual correction of certain aspects, especially if your tracking is relatively tight.

But those algorithms are for applying the kerning to the font file, not to the letters as they are generated from the font file.

Have you considered applying auto-kerning to the font file?

Fontforge (open source) and Fontlab (commercial) contain auto-kerning algorithms. They would have a relatively steep learning curve - you have to be familiar with technical aspects of how fonts work.

There is also iKern which is a guy that offers a commercial font-kerning service whereby he kerns your font for you and does a rather excellent job. I don't know how much it would cost.

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@Sims5801359

I haven't got time to think this through fully, or draw illustrations, but I had a half- idea based around first bisecting each glyph vertically.

Then for each half, determine two vertical axes:
- the bisector - exactly half between left and right extremes
- the "weight" axis - exactly half the ink on each side

Then move the adjacent neighbour glyph toward or away from the test half-glyph based on the relative positions of the two axes.

So, for example, in the pair "AV", the right half of the A is left-heavy and "attracts" the V; the left half of the V is right-heavy "attracts" the A, thus they are kerned together significantly.

However, I'm sure there's a flaw in that "AA" would be kerned together just as much as "AV".

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@Mendez620

This is a fairly simple algorithm I tried once, and may be good enough.

Render the characters in low resolution - say six or seven pixels tall (height of typical capital) about the same horizontally. You want a simple binary map of where there is empty space vs parts of the letter, on a simple low-res grid.

"Fatten" these letter maps. That is, fill each empty cell that's adjacent to a filled cell. This is to claim empty territory closest to the letter edges, so the neighboring letter doesn't get too close.

Play "horizontal Tetris" with the resulting letter maps. Let gravity act to the left. The bulging left-hand "belly" of the "a" will "fall" into the cavity under the overbar of the "T". How many cells did the "a" move? Scale that up in proportion to the actual size of the letters and that's how far to kern the actual high-res "a" leftward.

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