missing pixels in truetype non antialiased fonts

[fanoush]

Hello, since Chrome moved to fontations in version 136 truetype fonts are broken when font antialiasing is turned off. Here is screenshot how it looks now

tab title font is Tahoma and monotype font is Courier New. This basically happens in all fonts installed by ttf-mscorefonts-installer package in ubuntu/debian (Courier New, TimesNew Roman, Arial, ...)

related chromium bug is tracked here https://issues.chromium.org/issues/404881585

the original gentoo topic is here https://forums.gentoo.org/viewtopic-p-8862929.html?sid=99f37ed89d19ea4e9b96c2fa90ddd461

[jenskutilek]

It seems like TrueType dropout control is not implemented?

[behdad]

It seems like TrueType dropout control is not implemented?

Fontations doesn't have a rasterizer itself. Dropout control is a technique implemented in a scanline mono rasterizer. A relic of the far past I would say... But that's just me.

[fanoush]

Fontations doesn't have a rasterizer itself. Dropout control is a technique implemented in a scanline mono rasterizer.

Sorry, I don't understand technical details but the readme https://github.com/googlefonts/fontations?tab=readme-ov-file#structure says

skrifa is a mid level library that provides access to various types of metadata contained in a font as well as support for loading glyph outlines.
It's primary purpose is to replace FreeType in Google applications.

So does it belong to skrifa? It worked with FreeType before it was replaced by it.

[fanoush]

I have checked freetype and something is described here
https://freetype.org/freetype2/docs/reference/ft2-outline_processing.html#ft_outline_xxx
"By default, the scan converter will try to detect drop-outs in an outline and correct the glyph bitmap to ensure consistent shape continuity."

So which " scan converter" component does this "Outline Processing" part with Fontations?

[apodtele]

Perhaps, one could come up with a clever technique for gray to mono conversion without the legacy dropout control, something a little more clever than just thresholding at an arbitrary coverage, something based on local extrema.