Text quality on the Inky Impression 13.3" - Improvements to text rendering

[hpk60]

Hi Arne,
just got my Inky Impression, and it works fine with the Pi Zero 2W.
However, I see that the text is not as sharp as it could be.
Is there a reason, that 1600x1200 is not offered as resolution in the settings? This is the native resolution of the Inky Impression 13.3".
I could imagine, that the text would be sharper, if fugleramme could use to native resolution as an option. Am I wrong?

[arnegiacomo]

@hpk60 Fugleramme should automatically identify the screen resolution and render correctly using the official inky library. Could you upload an image of how it looks?

I've chosen fonts that should render well on an e-ink display, you could try different font sizes and styles to see if that helps. This also might be related to the specific hardware combo that I've not tested.

Running journalctl -u fugleramme-frame -n 100 --no-pager it should say something like:

Sep 12 00:47:04 fugleramme systemd[1]: Started fugleramme-frame.service - Fugleramme frame service (render loop + kiosk).
Sep 12 00:47:05 fugleramme uv[613250]: 2026-09-12 00:47:05,170 INFO Fugleramme v0.21.1
Sep 12 00:47:05 fugleramme uv[613250]: 2026-09-12 00:47:05,194 INFO Inky panel initialised: inky.inky_el133uf1 1600x1200

Heres an example I took some days ago with about 30 birds and 2 languages and the text reads cleanly (color of image became gray when I converted from heic to jpeg).

[hpk60]

Hi Arne,
thanks for the fast reply. You're right, it shows
Sep 12 12:49:11 PimoDisplay uv[919]: 2026-09-12 12:49:11,536 INFO Rendered collage page at 1200x1600

And it looks like this (just the text):

I think, it's okay and only visible with pixel peeping :-)
As you suggested, I will test with different fonts an sizes to see, if there's a setting, where's a bit better.

Thank you!

[arnegiacomo]

Theres room here for adding better fonts or other ways to display/render text. The text is not dithered, so its sharper, but maybe too sharp. I didn't spend much time on this when originally implementing it and I'm no expert in the field, so I'll take any inspiration or feedback for how we can make this better.

I haven't looked at what other e-ink programs do for rendering nice text, but this project can't be the only one with this challenge. I'll have a look around and keep this thread open so that others may come with ideas, feedback or inspiration too.

Thanks for the submission ❤️
(I'll rename the thread so others will more easily understand the topic)

[hpk60]

Okay, thanks. It's not a big issue, from a 'normal' distance, the text looks good, just when going close one could see, that there's some room for improvement ... Actually, I thought this could be a simple resaolution issue, therefore I opened this thread.

[arnegiacomo]

Hi again, I took a closer look again with fresh eyes.

The text on the e-ink panel is pure black with no grey edges, since grey would get dithered into coloured specks and the panel only has six colours and doesn't support individual pixel brightness. At this resolution it means some small stair-steps or pixels on curves when you look up close.

I tried some other ways of rendering the text on my own 13,3 panel. It either looked the same or worse. So I think this is about as good as we can get it with the current technologies.

If you want clearer text a larger label size or a heavier font will be the best solution. Otherwise we just have to wait for e-ink to become better.

I'll continue to keep this thread open in case people find some cool solution or something I missed and so that others that wonder the same might read the conclusions here.

[erendrake]

I dug into this on my own 13.3" and found one change in how the text is rasterized that helps.

The photo is a test page pushed straight to the panel. Each block is the same label at the same font, size and weight; only the rasterizing differs. "Before" is what the frame does today: draw the text antialiased, then cut the gray to black at a threshold. "After" draws into a Pillow mode "1" image instead (https://pillow.readthedocs.io/en/stable/handbook/concepts.html#modes), the 1-bit mode, which makes FreeType use its monochrome hinting: stems come out a whole number of pixels wide and baselines land on pixel rows. The layout is before|after over after|before, so every pair sits beside and above each other.

It shows most on the hairline faces at small sizes: Cormorant and EB Garamond lose strokes to gray dots on the before cells and hold together on the after cells. Gentium, the default, barely changes because its stems are already even. The sizes here are the 7.3" panel's medium and large (15 and 20 px), photographed on a 13.3". The stair-steps on curves that started this thread do not go away; that is the 150 ppi grid.

[arnegiacomo]

Thanks @erendrake, this is really useful - I'm not gonna pretend I understand everything here, but I didn't find this when first looking. Do you think this is easily applicable? If so feel free to submit a PR and I'll test it on both my 13,3 and 7,3 frames 👌

[arnegiacomo]

See 44bc109 - will be included in next release. Thanks for taking this up again!