Problem with font subsetting

[grumbles]

The subsetting feature is very useful. It will frequently reduce the space used for fonts by almost 90%. But on occasion it would appear to lose characters from the font. The examples below are with the small cap characters from LinBiolinum_RB. The first image is how the text appears in ADE without subsetting.

If I subset the font the heading looks like this:


With Calibre the result is similar except that the fallback font makes the error more obvious:


Is this a problem with Calibre? Is it an user error? Or what?

[grumbles]

Hmm. It would appear that the images in my post have gone AWOL. Is there a way to post images that are located on my machine, the insert image insists on a URL (which then disappeared).

[BetterRed]

Originally Posted by grumbles

Hmm. It would appear that the images in my post have gone AWOL. Is there a way to post images that are located on my machine, the insert image insists on a URL (which then disappeared).

@grumbles - Easiest way is to load them as attachments - click the paper clip in Advanced Mode

See also ==>> https://www.mobileread.com/forums/faq...b3_attachments

BR

[kovidgoyal]

Font subsetting currently does not support font-variant: small-caps or text-transform: capitalize

Adding support for both of those is certainly possible, but it's a lot of work for relatively rare use case.

[grumbles]

Thank you Red!

So here is the first, ADE with no subsetting:

and then with subsetting:

and the with Calibre and subsetted:

[grumbles]

and again, I'll eventually get it right.

[kovidgoyal]

Actually, I take it back, I had a look at the font subsetting code and it does automatically preserve small caps substitution rules and the target glyphs, open the subset font in fontforge and check the smcp tables under Element->Font Info->Lookups

[kovidgoyal]

And here is what the subset font looks like on my system in the calibre viewer:

[grumbles]

Well I've spent a fair bit of time looking at the fonts in FontForge and the their decomilation with ttx and I must admit that I'm in way over my head and I'm far outside my area of competence.

The font in question is LinBiolinum_RB. My first attempt was to copy the small cap glyphs from 0xE091 to replace the lowercase glyphs at 0x0061. This worked in that when I embedded the font, it would appear correctly, or at least it did after I removed the lower case ligatures that looked really funny with the surrounding small caps. When I subsetted the fonts, characters (and glyphs) went missing.

I then exported all the glyphs as svg images and created a new font by importing just the basic alphanumeric characters and punctuation. Again they display correctly and again when I subset them, characters are lost.

To check, I used a set of fonts that included small caps (Charis in this case) and everything was fine when I subsetted them. So there is something wrong with what or how I doing this. This is an area that I know nothing about. Any pointers to more information (other that the FontForge documentation, it is good but doesn't tell me the things I need to know) would be appreciated.

[kovidgoyal]

As I said, your example with Linolium RB works for me, see screenshot I posted. If you can provide a complete epub example file with embedded font that breaks on subsetting, that would help.

[JSWolf]

What is the code used to get ADE to display small caps from a font that also includes small caps?

[jackie_w]

Originally Posted by JSWolf

What is the code used to get ADE to display small caps from a font that also includes small caps?

I don't think any current Adobe reader software supports small-caps, does it? In theory, I think the @font-face is supposed to support the font-variant attribute just like it supports font-family, font-weight and font-style.

The only way I know to get true small-caps to work in epubs is to use a separate set of @font-faces for the small-caps-only font files. But you're probably doing that already.

If anyone knows different I'd also be interested to hear about it.

[JSWolf]

Originally Posted by jackie_w

I don't think any current Adobe reader software supports small-caps, does it? In theory, I think the @font-face is supposed to support the font-variant attribute just like it supports font-family, font-weight and font-style.

The only way I know to get true small-caps to work in epubs is to use a separate set of @font-faces for the small-caps-only font files. But you're probably doing that already.

If anyone knows different I'd also be interested to hear about it.

Yes, I am using a specific version of Charis SIL for smallcaps. On the SIL site is a font tuner that allows you to make a separate font for use as a smallcap font. It works very well. But, if it wasn't for Calibre's subsetting, embedding it along with the full other versions would make for a very large eBook.

[jackie_w]

Originally Posted by JSWolf

Yes, I am using a specific version of Charis SIL for smallcaps. On the SIL site is a font tuner that allows you to make a separate font for use as a smallcap font. It works very well. But, if it wasn't for Calibre's subsetting, embedding it along with the full other versions would make for a very large eBook.

I'm also using your Charis small-caps font files, but I've never bothered embedding them. I just use @font-faces to reference them as font files sideloaded once per device (Sony, Kobo, Pocketbook, android).

[JSWolf]

Originally Posted by jackie_w

I'm also using your Charis small-caps font files, but I've never bothered embedding them. I just use @font-faces to reference them as font files sideloaded once per device (Sony, Kobo, Pocketbook, android).

Give my new version a try. I've found a very good program that was able to add kerning and they look even better on eInk now. I would be very interested in your opinion. Thanks.

https://www.mobileread.com/forums/sho...d.php?t=184056