// rasterize returns the advance width, glyph mask and integer-pixel offset // to render the given glyph at the given sub-pixel offsets. // The 24.8 fixed point arguments fx and fy must be in the range [0, 1). func (c *Context) rasterize(glyph truetype.Index, fx, fy raster.Fix32) ( raster.Fix32, *image.Alpha, image.Point, error) { if err := c.glyphBuf.Load(c.font, c.scale, glyph, truetype.Hinting(c.hinting)); err != nil { return 0, nil, image.Point{}, err } // Calculate the integer-pixel bounds for the glyph. xmin := int(fx+raster.Fix32(c.glyphBuf.B.XMin<<2)) >> 8 ymin := int(fy-raster.Fix32(c.glyphBuf.B.YMax<<2)) >> 8 xmax := int(fx+raster.Fix32(c.glyphBuf.B.XMax<<2)+0xff) >> 8 ymax := int(fy-raster.Fix32(c.glyphBuf.B.YMin<<2)+0xff) >> 8 if xmin > xmax || ymin > ymax { return 0, nil, image.Point{}, errors.New("freetype: negative sized glyph") } // A TrueType's glyph's nodes can have negative co-ordinates, but the // rasterizer clips anything left of x=0 or above y=0. xmin and ymin // are the pixel offsets, based on the font's FUnit metrics, that let // a negative co-ordinate in TrueType space be non-negative in // rasterizer space. xmin and ymin are typically <= 0. fx += raster.Fix32(-xmin << 8) fy += raster.Fix32(-ymin << 8) // Rasterize the glyph's vectors. c.r.Clear() e0 := 0 for _, e1 := range c.glyphBuf.End { c.drawContour(c.glyphBuf.Point[e0:e1], fx, fy) e0 = e1 } a := image.NewAlpha(image.Rect(0, 0, xmax-xmin, ymax-ymin)) c.r.Rasterize(raster.NewAlphaSrcPainter(a)) return raster.Fix32(c.glyphBuf.AdvanceWidth << 2), a, image.Point{xmin, ymin}, nil }
func (f *font) glyph(r rune) *glyph { if g, found := f.glyphs[r]; found { return g } idx := f.ttf.Index(r) gb := truetype.NewGlyphBuf() err := gb.Load(f.ttf, f.scale, idx, truetype.Hinting(truetype.FullHinting)) if err != nil { panic(err) } g := glyph(*gb) f.glyphs[r] = &g return &g }