Paste Special... font to font if Units per em values differ

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Location: Worcestershire, England

Paste Special... font to font if Units per em values differ

Post by William » Fri Aug 31, 2012 11:01 am

I was experimenting, musing on future possibilities for my research on Communication through the Language Barrier.

So, I made a copy of an open source font, the licence of the particular font allows the making of derivative fonts, with the copy having derivative_test.ttf as the file name. I used FontCreator to make the copy using the File Save As.. feature of FontCreator.

The font has accented characters for many European languages.

I noted that the font has a Units per em value of 1000.

My idea was to add to the font, at U+E001, which is in the plane 0 Private Use Area of the character map, a copy of the glyph that is mapped to U+E001 in my Localizable Sentences 027 font. This being a test for the future possibility of adding the whole collection of mapped glyphs from plane 0 of the Localizable Sentences 027 font.

The Localizable Sentences 027 font has a Units per em value of 2048.

I realized that the glyph at U+E001 would need some scaling down in size once it was pasted into the derivative_test.ttf font.

So I decided to open Localizable Sentences 027, copy the whole glyph that is mapped to U+E001 onto the clipboard from the FontCreator overview window, then add an empty cell at the end of derivative_test.ttf and use Edit Paste Special... with all four checkboxes ticked, with the option set to the default of Keep same mappings, to paste the glyph from the clipboard into the new cell.

A test of a mixed sentences as follows was tried, within the FontCreator Font Test... facility.

How does this look?

It seemed to look much better than I had expected it would look without some scaling down of the size of the U+E001 glyph.

Upon investigation, I found that the pasted glyph had been scaled by a factor of 1000/2048 in the course of the Paste Special... operation, including changing the Advance Width from 6144 font units to 3000 font units.

In the event, as a design decision I used the Glyph Transformer to then scale the glyph by 75% both horizontally and vertically and the Advance Width ended up as at 2250 font units as a result of that scaling process. This was so that the height of the symbol would be a little less than the capitals height of the letters of the font. Checking back, the symbols are much larger than the capital height in the Localizable Sentences 027 font, so the 75% scaling is really just because of the way that I had designed the symbols in the first place when I started designing them some years ago.

What I find interesting, and helpful, is that the Paste Special.. automatically scaled the glyph as it was copied from one font to another font.

William Overington

31 August 2012

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