// Render draws rune r front the specified font at the specified dpi and scale. It returns a
// grayscale image that is just large enough to contain the rune.
func Render(font *truetype.Font, r rune, dpi, scale float64) (*image.Gray, error) {
glyph := truetype.NewGlyphBuf()
index := font.Index(r)
glyph.Load(font, font.FUnitsPerEm(), index, truetype.FullHinting)
ctx := freetype.NewContext()
boxer := makeBoundingBoxer()
ctx.SetSrc(image.NewUniform(color.White))
ctx.SetDst(boxer)
ctx.SetClip(boxer.largeBounds)
ctx.SetFontSize(250)
ctx.SetDPI(dpi)
ctx.SetFont(font)
if err := glyph.Load(font, font.FUnitsPerEm(), font.Index(r), truetype.FullHinting); err != nil {
return nil, fmt.Errorf("Unable to load glyph: %v\n", err)
}
var rp raster.Point
rp.X = ctx.PointToFix32(0)
rp.Y = ctx.PointToFix32(100)
ctx.DrawString(string(r), rp)
boxer.complete()
g := gift.New(
gift.Resize(int(float64(boxer.Bounds().Dx())*scale+0.5), int(float64(boxer.Bounds().Dy())*scale+0.5), gift.CubicResampling),
)
dst := image.NewGray(g.Bounds(boxer.Bounds()))
g.Draw(dst, boxer)
return dst, nil
}
