What are fractional metrics? What are the consequences of setting the fractional metrics rendering hint on text performance, readability etc? When should I use it?
A. In short fractional metrics doesn’t affect performance. Principally it affects the spacing between glyphs (characters) which on low resolution (screen) devices can degrade the overall legibility of the text. Understanding this requires some explanation of the topic. “Fractional metrics” is sometimes called “Printer matching” on other platforms. It refers to the fact that characters in a font are optimized for particular font size and output device resolution to improve legibility of text. These optimizations involve rounding to the pixel grid and therefore may affect overall widths of individual glyphs as well as distances between them. The text display system can either choose to round these “advance widths” to an integer so that the text will have consistent spacing, or it can accumulate the positions of the characters using the unrounded, or fractional, values.
Related Questions
- What are fractional metrics? What are the consequences of setting the fractional metrics rendering hint on text performance, readability etc? When should I use it?
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