Kobo's font rendering problem... have they fixed it?

[Elswyth]

I have a Kobo Aura HD and I'm currently running 2.5.1 (or possibly 2.8.1) Firmware on it because I hated the 3.0 update so much. The font rendering changed dramatically and it appeared that the anti-aliasing for all text across the entire interface had been changed for some reason.

I've upgraded again a couple of times since then but each time I saw that the same problem was there. From various posts on the web with screenshots of the latest devices it seems as though the issue still exists.

For comparison, here's an image showing what I mean. Nobody else seems to be able to tell the difference, but to my eye the rendering of Georgia across these two examples could not be more different. The newer version, on the right, appears to have completely different anti-aliasing, and the letterforms appear squished and deformed.

I'm hoping and praying that one day it goes back to how it used to be. Has anyone else noticed this problem, or has it been fixed since I've been banished back to downgraded Firmware, never to sync over WiFi again?

[davidfor]

I can see a difference between the two screens, but I can't really tell if the font rendering is different. The are so many differences between them that my eye is distracted to much to be able to see if it a font rendering issue, a configuration issue or just a difference in the photos (the colour is distracting and the left is slightly blurred to my eye). To be able to tell, you need to use the same page of the same book, the same font settings, the same lighting and camera. You could also use the screenshot function of the device to eliminate the external variables.

[GeoffR]

I noticed that the base sharpness setting did seem to change in some firmware versions, there were a couple of versions around 3.11.0 (can't remember exactly) where the sharpness was lower, then later it was increased again. The base weight might have changed a bit in some versions too.

If you wanted to get it exactly the same as it was in a particular older firmware version then you'd need to adjust the weight/sharpness settings to match by eye, as they changed the base sharpness not the default setting. I.e. setting readingFontSharpness\Georgia=0.10 won't necessarily give the same actual sharpness in all firmware versions. 0.10 in one version might be equal to 0.15 in another version.

Unfortunately the separate sharpness slider disappeared after version 3.1.1 so for later versions you'll need to adjust the sharpness by editing the configuration file.

Edit: You could use the weight/sharpness demonstration kepub in this post to help make the adjustments. If you take a screenshot with it set how you like it on your old firmware, then another screenshot in the new firmware, you should be able to work out by comparing the screenshots side by side how much you need to adjust the sharpness to get it to match.

[GeoffR]

I thought of another thing: Way back in firmware 2.8.1 the font hinting might not have been enabled by default, which in later firmware it is. In current firmware the built-in stylesheet has an item body { -kobo-font-hintstyle: 1; } to turn on hinting which doesn't seem to be present in firmware 2.8.1

There have been a number of observations that hinting doesn't seem to help on an e-ink screen, and there are some cases where it makes the font look much worse. You could try turning off the hinting in later firmware and see if that makes it look more like what you see in 2.8.1, either by modifying the kepub book's stylesheet to set body { -kobo-font-hinstyle: 0 !important; } (I haven't tested that) or by stripping the hinting from the font itself.

Edit: This post has screenshots showing a (fairly extreme) example of how much a font can be improved by removing the hinting.

Edit2: Firmware version 3.1.0 was the first that had -kobo-font-hintstyle: 1; in the stylesheet.

[Elswyth]

Thank you so much GeoffR! That is all so interesting and I'm so grateful to you for sharing your knowledge on the subject (and making me feel less like I'm the only one seeing things and am therefore going mad). To me it seems like the hinting is the most likely culprit, especially if it was introduced in 3.1.0 which is quite possibly the update I am referring to and I'm just remembering it incorrectly as being 3.0.

I will definitely start investigating a few of things and see what happens! I'll try modifying a kepub stylesheet first as that seems the easiest thing to try initially.. I'm not well-versed on how you would remove hinting from a font file.

[GeoffR]

Originally Posted by Elswyth

I will definitely start investigating a few of things and see what happens! I'll try modifying a kepub stylesheet first as that seems the easiest thing to try initially.. I'm not well-versed on how you would remove hinting from a font file.

I tried setting -kobo-font-hintstyle: 0; in a kepub stylesheet, but it didn't make the slightest bit of difference to the rendering of the built-in fonts on my Glo with firmware 3.16.0, so it might be that the only way is to strip the hinting from the fonts. That is easy to do with fontforge for sldeloaded fonts, but I don't know any way to change the built-in fonts.

BTW I can't see any problems with the rendering of the built-in fonts at all, although I don't use them much anymore, they look fine to me apart from the fact that some such as Georgia lack kerning, and that the KEPUB reader doesn't support ligatures (one on the reasons I prefer the EPUB reader.)

Edit: The only difference I can see in your example photos is that the one on the right looks a bit sharper and a bit lighter, but it is hard to tell if that is the sharpness/weight settings or just because of the difference in font size and a better photo. Having actual screenshots to compare could make a difference.

[GeoffR]

I think we can forget about the -kobo-font-hintstyle idea. I patched the firmware to change the setting from 1 to 0 in the built-in stylesheet but it didn't make any difference at all to the rendering. I took a screenshot in the KEPUB reader with Georgia selected, and the PNG screenshots before and after patching were byte-for-byte identical. So either -kobo-font-hintstyle does nothing or Georgia had no hinting to start with.

[GeoffR]

I found these screenshots I had posted here when firmware 3.1.0 was released, comparing the same book on a

• Mini with firmware 2.6.2

• Glo with firmware 3.1.0

The screen resolution and font size is different, and there is a fault with the KEPUB formatting in 3.1.0 to do with the spacing between the chapter header and the text. But apart from the layout differences I can't see any obvious difference in the font rendering regards anti-aliasing, hinting, or anything. Having a screenshot from the save device would be better of course.

[s4nder]

I just wish Georgia had kerning and ligatures. I can no longer use it, knowing it's the only half-assed font on the device.

[GERGE]

Can you share hinting patch for 3.15? I can try with some hinted types. If it works, it would save a great amount of time while testing typefaces.

And I don't think included typefaces has hints.

[Elswyth]

Originally Posted by GeoffR

I found these screenshots I had posted here when firmware 3.1.0 was released, comparing the same book on a

• Mini with firmware 2.6.2

• Glo with firmware 3.1.0

The screen resolution and font size is different, and there is a fault with the KEPUB formatting in 3.1.0 to do with the spacing between the chapter header and the text. But apart from the layout differences I can't see any obvious difference in the font rendering regards anti-aliasing, hinting, or anything. Having a screenshot from the save device would be better of course.

That's hilarious because to me those two images are like chalk and cheese! The shapes of the letters look so incredibly different.

I'll take a screenshot on my device and then upgrade the firmware and take another of the exact same page with the same weight/sharpness settings so that we can compare.. maybe I can show some of the letters side by side.

Thanks so much for trying the -kobo-font-hintstyle! What a shame that there is no apparent change. I wonder what it *is* that's causing this difference!

[GeoffR]

Originally Posted by Elswyth

That's hilarious because to me those two images are like chalk and cheese! The shapes of the letters look so incredibly different.

I'll take a screenshot on my device and then upgrade the firmware and take another of the exact same page with the same weight/sharpness settings so that we can compare.. maybe I can show some of the letters side by side.

Thanks so much for trying the -kobo-font-hintstyle! What a shame that there is no apparent change. I wonder what it *is* that's causing this difference!

It'll be interesting to see the screenshots. If possible could you get shots from an epub as well as a kepub? They use completely different rendering code, but the epub code didn't change at all between firmware 2.1.5 and 3.4.1 until a major update in firmware 3.5.0 (although it would still have been affected by the many changes to things like font sizes, line spacing, weight and sharpness etc.)

[Elswyth]

Ok! I've finally got some screenshots to share.. I forgot to do the epubs unfortunately! I can do that soon, but for now here are some kepub shots.

So, just to reiterate, I realise that these changes are slight. But to me, they affect the entire reading experience; it just looks so different to me. More than that, though, I just don't even understand what the difference is, or what's causing it, and why the change occurred or was necessary.

I've shown comparable screenshots of the same page with Georgia and Malabar as two main examples, and I've also included a couple of GIFs that I hope illustrate the differences.

I'm fully aware that some people will say 'they look exactly the same' but I vehemently disagree It looks worse on the actual Aura HD to me as well.

[davidfor]

I can see the differences, but I don't know how to describe them. And I don't know which I prefer.

I suspect the differences are in the font rendering engine. Kobo probably has changed that somewhere along the way, but I'm not sure. What I do know has changed is the advanced settings for the included fonts. With 2.8.1, there where two sliders for sharpness and weight. With 3.15.0, there is only one. If you have played with these at any time, you might want to reset them.

There have been other changes. For example, with 2.8.1, all the devices had the same list of font sizes. With 3.15.0, different devices get a different set of sizes. I don't think this is what you are seeing, but if you are relying on putting the font size slider in the same place with the different firmware, you might get a different size. There have been other changes such as how the line height gets interpreted, but again, that shouldn't affect this. Though that might be why there are a different number of lines per screen. Though why Georgia has one extra and Malabar has one less with 3.15.0, I'm not sure. Actually, I think Kobo has said something about reading the information from the fonts files differently or better or something.

Because of the above, it might be useful to check what is in the config file. These settings are in the "Reading" section. Removing all the lines in the section will reset them to defaults when a new book is opened. Or the individual settings can be removed or changed. The only catch with doing this is that when you change the settings, they are also stored in the database against that book. That means that reopening the book will use the settings from the database, but opening a new book will use the settings from the config file. The sharpness and weight settings always come from the config file.

Have you tried a sideloaded font? As there is some special handling for the included fonts, at least for the sharpness/weight settings, there might be other special handling. If a sideloaded font looks different between the two firmware, it suggests the rendering engine has changed. If they are the same, it is probably something about how the included fonts are handled.

[howyoudoin]

Elswyth, the strange thing is that when I first saw the comparison in your initial post, my first thought was that the 2.8.1 Georgia was narrower than the 3.15.1 version. I left with the impression that they'd reduced the x-height in 3.15.1. I'm not very proficient with typography except from whatever knowledge I've gleaned from wikipedia, so I might be explaining it wrong technically. Personally I preferred the 2.8.1 version.

But now that I see your latest screenshots, I have the exact opposite impression. The animation makes it apparent to me that I prefer the newer font that seems bolder and slightly taller.