Hinting

Hinting adjusts the outline of a glyph so that its stems and edges fall on whole pixels. At small sizes on a screen, hinted text is sharper. At large sizes, in print, and in vector output such as PDF and SVG, hinting has little benefit and changes the shapes from the design.

Turn hinting on

TextOptions options = new(font)
{
    HintingMode = HintingMode.Standard,
    Dpi = 96,
};

HintingMode	Effect
None (default)	Use the outlines as designed.
Standard	Run the TrueType hinting instructions in the font.

Set Dpi to the real resolution of the target. Hinting fits the outline to the pixel grid at that resolution, so the wrong DPI gives the wrong result.

What hinting applies to

• Only fonts with TrueType outlines (glyf table) are hinted. The library does not hint CFF and CFF2 outlines (.otf fonts with PostScript outlines). For those fonts Standard has no effect.
• Hinting changes the outlines that your glyph renderer gets. When hinting is on, the library also rounds the positions of attached marks (accents) to whole pixels. The advances of the glyphs, and so the measurements of the text, do not change.

Faulty hint programs

Some fonts have hinting instructions with errors. When the instructions of a glyph fail, the library uses the glyph's outline without hinting, and continues. One bad glyph does not stop the text from rendering.

Threads

Hinting is safe to use from more than one thread with the same Font. The library runs the hinting instructions of one font on one thread at a time, so heavy parallel rendering of the same hinted font can wait on that lock.