Font rasterization
In Microsoft's terminology, this is called bi-level (and more popularly "black and white") rendering because no intermediate shades (of gray) are used to draw the glyphs.
Most computer displays have pixels made up of multiple subpixels (typically one each for red, green, and blue, which are combined to produce the full range of colours).
[3] Mac OS X's Quartz is distinguished by the use of subpixel positioning; it does not force glyphs into exact pixel locations, instead using various antialiasing techniques,[4] including subpixel rendering, to position characters and lines to appear further from the type designer's intent of hinting and closer to the original outline.
The result is that the on-screen display looks extremely similar to printed output, but can occasionally be difficult to read at smaller point sizes.
This change is acceptable to HiDPI "retina" screens, but makes text on external monitors harder to read.
[5] Most other systems use the FreeType library, which depending on the settings, can fall anywhere between Microsoft's and Apple's implementations; it supports hinting and anti-aliasing, and optionally performs subpixel rendering and positioning.
FreeType also offers some features not present in either implementation such as color-balanced subpixel rendering and gamma correction.
upright=
multiplier from
1.70
to
1.75
results in significant and mutually distinct rendering anomalies, possibly due to rounding errors resulting from use of integer font sizes.
[
original research?
]
