A Questoin about bearings.

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PJMiller
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A Questoin about bearings.

Post by PJMiller » Fri Feb 05, 2016 11:18 pm

If a glyph is multi mapped, i.e. a single glyph with more than one code point, are the bearings set more than once by the 'Optical Metrics' tool or is it just treated as a single glyph?

Is the glyph processed once for each codepoint or just once?

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Re: A Questoin about bearings.

Post by Erwin Denissen » Fri Feb 05, 2016 11:23 pm

It is set only once, but the algorithm that calculates it, does depend on the code points.
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Re: A Questoin about bearings.

Post by PJMiller » Fri Feb 05, 2016 11:33 pm

Optical Metrics does not set the bearings of the whole font, just a large number of them, others are left unchanged, at least that is how I understand it to work, please correct me if I am wrong.

But the algorithm must take the shape of the glyph into account, I can imagine the capital letter 'A' with various different shapes and the algorithm must be able to cope with this variation, so this leads on to the obvious question can this not be applied to any or all glyphs?

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Re: A Questoin about bearings.

Post by Bhikkhu Pesala » Fri Feb 05, 2016 11:54 pm

To process all glyphs would take too long. If you calculate metrics for the base glyphs, then complete composites, the composite glyphs will adopt the same metrics.

See my tip for processing other alphabets such as Small Caps.
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Re: A Questoin about bearings.

Post by PJMiller » Sat Feb 06, 2016 10:06 am

Optical Metrics processes a very large number of glyphs, but not all of them. I don't know how it decides which ones to do, if there is a preset list of glyphs it will process or what it does.

On Kelvinch it takes a long time, this is not a complaint, it has a lot to do, I understand why it takes a long time and just leave the computer to do it's thing and go to do something else.

I'm just curious as to how it decides which glyphs to process and which ones to leave alone.

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Re: A Questoin about bearings.

Post by Bhikkhu Pesala » Sat Feb 06, 2016 10:51 am

In this post:-
Erwin Denissen wrote:The list of characters that will be processed by the optical metrics feature is:

abc..xyz
ABC..XYZ
0123456789
!"#$%&'()*+,-./:;<=>?@©€
That's not very many (86), but since each one is combined with all of the others, that's a lot of pairs — 7,310 if my maths is correct.
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Re: A Questoin about bearings.

Post by PJMiller » Sat Feb 06, 2016 11:27 am

I followed the link and read the post but I don't understand the discrepancy between what is being said and my own experience.

If Optical Metrics only processes the characters :-

abc..xyz
ABC..XYZ
0123456789
!"#$%&'()*+,-./:;<=>?@©€

Then the runtime should be constant assuming all those characters are present in the font.

But that is not my experience.

When I run Optical Metrics I see a great many more characters being processed in the dialog box which appears and the runtime of the process has gradually increased as Kelvinch has got bigger.

Perhaps Erwin could enlighten me as to what is going on?

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Re: A Questoin about bearings.

Post by Bhikkhu Pesala » Sat Feb 06, 2016 12:40 pm

Yes, you're right, the Optical Metrics now also processes the composites used by those base characters.

If you watch you will see something like:-
  1. Analysing A-Z, Processing a-z
  2. Analysing a-z, Processing A-Z
  3. Analysing 0-€, Processing 0-
  4. Processing Á to Ẃ (or whatever composites exist in the font
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Re: A Questoin about bearings.

Post by Erwin Denissen » Sat Feb 06, 2016 1:02 pm

Since version 9, Optical Metrics processes the characters:

All Latin upper and lower case characters, including abc..xyz and ABC..XYZ as well as the digits 0123456789 and several other characters (mainly punctuation) !"#$%&'()*+,-./:;<=>?@©€
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