Retrieving Character Outlines

You can use the GetGlyphOutline function to retrieve the outline of a glyph from a TrueType font. The glyph outline returned by the GetGlyphOutline function is for a grid-fitted glyph. (A grid-fitted glyph has been modified so that its bitmap image conforms as closely as possible to the original design of the glyph.) If your application requires an unmodified glyph outline, request the glyph outline for a character in a font whose size is equal to the font's em units. (To create a font with this size, set the lfHeight member of the LOGFONT structure to the negative of the value of the ntmSizeEM member of the NEWTEXTMETRIC structure.)

GetGlyphOutline returns the outline as a bitmap or as a series of polylines and splines. When an application retrieves a glyph outline as a series of polylines and splines, the information is returned in a TTPOLYGONHEADER structure followed by as many TTPOLYCURVE structures as required to describe the glyph. All points are returned as POINTFX structures and represent absolute positions, not relative moves. The starting point given by the pfxStart member of the TTPOLYGONHEADER structure is the point where the outline for a contour begins. The TTPOLYCURVE structures that follow can be either polyline records or spline records.

To render a TrueType character outline in Windows, you must use both the polyline and the spline records. Windows can render both polylines and splines easily. Each polyline and spline record contains as many sequential points as possible, to minimize the number of records returned.

The starting point given in the TTPOLYGONHEADER structure is always on the outline of the glyph. The specified point serves as both the starting and ending points for the contour.

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