Sideloaded fonts best practices/rules

[sherman]

Before we start, I'm no font designer. I don't know a lot about fonts. All the information in this post I've gathered from this forum, and/or my own observations.

So I wanted to consolidate as much of the font rules and best practices for the Kobo as I could into one post. Currently this information is scattered about multiple posts over many threads. Here goes:

Font Naming:
The Kobo is very strict about how fonts should be named. The filename of the font files should be as follows

FontName-Regular.xxx OR FontName.xxx
FontName-Italic.xxx
FontName-Bold.xxx
FontName-BoldItalic.xxx

Where FontName matches that of the internal font name EXACTLY, and xxx is otf OR ttf

There may be other font naming conventions that are allowed, but this seems to be the most common, and guaranteed to work.


OpenType or TrueType?

This is not actually quite the correct question...
It should be PostScript Outlines or TrueType Outlines?, with OpenType Layout.
By convention it seems that PS outline fonts have an extension of .otf whereas TT outline fonts have an extension of .ttf

So which to use? If you wish to use the Advanced Font Control on the Kobo, then fonts with TrueType outlines should be used. Otherwise it doesn't seem to matter too much.

Kerning:
Adobe RMSDK (epub) seems to make use of the more advanced GPOS for kerning, however, the ACCESS (kepub) only recognizes the "Legacy" kerning features.

If you only read epub, there is no need to add legacy kerning support to the font. Otherwise, for kerning support in kepub, the legacy kerning table is required to be added to the font.

PANOSE:

PANOSE information can be used by applications to identify the characteristics of a font. However in kobo devices.....

Lets just say, that Kobo Nickel gets very confused very easily when it comes to PANOSE. I don't know what parts are problematic, and what is not. I personally completely remove the information (set all fields to 0, or Any), which Nickel seems quite happy about.

Indications of PANOSE problems in Nickel are the font selection list displaying the font in bold and/or italic, rather than the regular variant that it should. This also shows in the page numbers at the bottom of the screen.

Hinting:

Hinting will generally have no noticeable effects. There are some cases it can have a detrimental effect however. This seems to be the case with hand-hinted fonts for the most part. If a font looks ugly/uneven, chances are it could be a hinting, and you should try stripping hints from the font to see if that improves matters.


Hopefully I have covered the main points in this post, and that people find it useful. If anybody has any additions or corrections, please let me know, and I will update the post.

[Anak]

Originally Posted by sherman

Hinting:

Hinting will generally have no noticeable effects. There are some cases it can have a detrimental effect however. This seems to be the case with hand-hinted fonts for the most part. If a font looks ugly/uneven, chances are it could be a hinting, and you should try stripping hints from the font to see if that improves matters.

True, if a font doesn't look smooth it is most likely a hinting problem and it can affect any type of font. However, you do not have to remove the hinting info from the font. Just update it.

I had this issue with some Adobe fonts which I had slightly thickened to improve the visibility of the regular and italics sub family font types. I used FontLab Studio to do this and experimenting with the (auto) hinting settings/parameters of FontLab Studio didn't make the font more smooth.

My advice: the best way to fix hinting issues is to use the freeware tool Type Lite (http://www.cr8software.net/typelight.html). Open the problematic font and choose the menu entry Global > Convert to TT curves or Convert to PS curves. Then save (or overwrite) the font as .ttf (TT curves) or .otf (PS curves). After that your font will look much smoother.
You can use this tool to convert fonts from TTF to OTF and vice versa by using the procedure above.
You can also use the same tool to fix other font issues (internal naming, etc.).

[sherman]

Originally Posted by Anak

True, if a font doesn't look smooth it is most likely a hinting problem and it can affect any type of font. However, you do not have to remove the hinting info from the font. Just update it.

I had this issue with some Adobe fonts which I had slightly thickened to improve the visibility of the regular and italics sub family font types. I used FontLab Studio to do this and experimenting with the (auto) hinting settings/parameters of FontLab Studio didn't make the font more smooth.

My advice: the best way to fix hinting issues is to use the freeware tool Type Lite (http://www.cr8software.net/typelight.html). Open the problematic font and choose the menu entry Global > Convert to TT curves or Convert to PS curves. Then save (or overwrite) the font as .ttf (TT curves) or .otf (PS curves). After that your font will look much smoother.
You can use this tool to convert fonts from TTF to OTF and vice versa by using the procedure above.
You can also use the same tool to fix other font issues (internal naming, etc.).

That's basically what I meant by removing hinting, converting or regenerating the font file without hinting, or with autohinting.

EDIT: That program looks interesting. I had a very quick look, and as a free tool, it has one major issue that affects modifying fonts for kobo devices. It does not allow modifications of the PANOSE information.