关于emf的单位问题

CreateEnhMetaFile(
HDC hdcRef, // handle to reference DC
LPCTSTR lpFilename, // file name
CONST RECT* lpRect, // bounding rectangle
LPCTSTR lpDescription // description string
);
PlayEnhMetaFile(
HDC hdc, // handle to DC
HENHMETAFILE hemf, // handle to an enhanced metafile
CONST RECT *lpRect // bounding rectangle
);
这两个函数中lpRect 的单位应该如何理解