EPUB to PDF odd letter spacing

Books987 · 01-26-2015, 08:11 PM

Does anyone know why the letters are spaced out oddly? Especially in the bold-faced print.

Example:

Here's an example of what the spacing should look like:

Is this something that can be fixed in Calibre or is this a flaw in the PDF converison process? Thanks.

kovidgoyal · 01-26-2015, 08:20 PM

It depends on the font used, some fonts work much better than other, you will have to experiment.

Books987 · 01-26-2015, 08:22 PM

Quote:

Originally Posted by kovidgoyal

It depends on the font used, some fonts work much better than other, you will have to experiment.

Ok, thanks. So what causes it? That's not what the font is supposed to look like.

kovidgoyal · 01-26-2015, 08:25 PM

I've never looked into it in detail, but I suspect the underlying cause is that the Qt text rendering library (that the PDF output uses) does not support some form of kerning data, either in the KERN or GPOS font tables.

Books987 · 01-26-2015, 08:28 PM

That makes sense. So I guess the fonts that will look good are the ones that have more regular spacing and aren't screwed up by that.

It's weird that bold fonts are so affected by it though.

kovidgoyal · 01-27-2015, 05:21 AM

That can happen if the font family does not have an actual bold face, so that the text rendering engine uses simulated bold, which means basically drawing the characters twice with a slight offset. This looks pretty bad in PDF.

01-26-2015, 08:11 PM	#1
Books987 Member Posts: 11 Karma: 10 Join Date: Jan 2015 Device: none	EPUB to PDF odd letter spacing Does anyone know why the letters are spaced out oddly? Especially in the bold-faced print. Example: Here's an example of what the spacing should look like: Is this something that can be fixed in Calibre or is this a flaw in the PDF converison process? Thanks.

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01-26-2015, 08:20 PM	#2
kovidgoyal creator of calibre Posts: 43,835 Karma: 22666666 Join Date: Oct 2006 Location: Mumbai, India Device: Various	It depends on the font used, some fonts work much better than other, you will have to experiment.

01-26-2015, 08:25 PM	#4
kovidgoyal creator of calibre Posts: 43,835 Karma: 22666666 Join Date: Oct 2006 Location: Mumbai, India Device: Various	I've never looked into it in detail, but I suspect the underlying cause is that the Qt text rendering library (that the PDF output uses) does not support some form of kerning data, either in the KERN or GPOS font tables.

01-26-2015, 08:28 PM	#5
Books987 Member Posts: 11 Karma: 10 Join Date: Jan 2015 Device: none	That makes sense. So I guess the fonts that will look good are the ones that have more regular spacing and aren't screwed up by that. It's weird that bold fonts are so affected by it though.

01-27-2015, 05:21 AM	#6
kovidgoyal creator of calibre Posts: 43,835 Karma: 22666666 Join Date: Oct 2006 Location: Mumbai, India Device: Various	That can happen if the font family does not have an actual bold face, so that the text rendering engine uses simulated bold, which means basically drawing the characters twice with a slight offset. This looks pretty bad in PDF.