关于FreeType的ppem含义

Posted 2023-03-05 柳鲲鹏

　　继上文吾做了一系列粗体研究之后，负责FreeType的老外看了觉得ppem更靠谱。可是ppem离WORD效果相差较大。吾表示不知道ppem的意思，建议使用72，即point转pixel的单位。老外怒了！

Ouch. Please educate yourself! This is the most important unit for FreeType; it means 'pixels per em', where 'em' refers to the width of the 'm' character (or the 'em' dash). Contrary to point values, which depend on the DPI value and can thus be non-integer, the ppem value is always an integer. For example, all hinting instructions in TrueType fonts are firmly based on ppem values. The conversion formula is
ppem = pt * DPI / 72

See https://freetype.org/freetype2/docs/glyphs/glyphs-2.html for more.

第一句话的意思，用中文说，大约是你看看你一天天的……这部分我也确实没有仔细研究就是，不丢脸，哈哈。

我继续研究一下。