Exemplo n.º 1
0
// DrawString draws s at p and returns p advanced by the text extent. The text
// is placed so that the left edge of the em square of the first character of s
// and the baseline intersect at p. The majority of the affected pixels will be
// above and to the right of the point, but some may be below or to the left.
// For example, drawing a string that starts with a 'J' in an italic font may
// affect pixels below and left of the point.
// p is a raster.Point and can therefore represent sub-pixel positions.
func (c *Context) DrawString(s string, p raster.Point) (raster.Point, error) {
	if c.font == nil {
		return raster.Point{}, errors.New("freetype: DrawText called with a nil font")
	}
	prev, hasPrev := truetype.Index(0), false
	for _, rune := range s {
		index := c.font.Index(rune)
		if hasPrev {
			p.X += c.FUnitToFix32(int(c.font.Kerning(prev, index)))
		}
		mask, offset, err := c.glyph(index, p)
		if err != nil {
			return raster.Point{}, err
		}
		p.X += c.FUnitToFix32(int(c.font.HMetric(index).AdvanceWidth))
		glyphRect := mask.Bounds().Add(offset)
		dr := c.clip.Intersect(glyphRect)
		if !dr.Empty() {
			mp := image.Point{0, dr.Min.Y - glyphRect.Min.Y}
			draw.DrawMask(c.dst, dr, c.src, image.ZP, mask, mp, draw.Over)
		}
		prev, hasPrev = index, true
	}
	return p, nil
}
Exemplo n.º 2
0
func main() {
	const (
		n = 17
		r = 256 * 80
	)
	s := raster.Fix32(r * math.Sqrt(2) / 2)
	t := raster.Fix32(r * math.Tan(math.Pi/8))

	m := image.NewRGBA(image.Rect(0, 0, 800, 600))
	draw.Draw(m, m.Bounds(), &image.Uniform{color.RGBA{63, 63, 63, 255}}, image.ZP, draw.Src)
	mp := raster.NewRGBAPainter(m)
	mp.SetColor(image.Black)
	z := raster.NewRasterizer(800, 600)

	for i := 0; i < n; i++ {
		cx := raster.Fix32(25600 + 51200*(i%4))
		cy := raster.Fix32(2560 + 32000*(i/4))
		c := raster.Point{cx, cy}
		theta := math.Pi * (0.5 + 0.5*float64(i)/(n-1))
		dx := raster.Fix32(r * math.Cos(theta))
		dy := raster.Fix32(r * math.Sin(theta))
		d := raster.Point{dx, dy}
		// Draw a quarter-circle approximated by two quadratic segments,
		// with each segment spanning 45 degrees.
		z.Start(c)
		z.Add1(c.Add(raster.Point{r, 0}))
		z.Add2(c.Add(raster.Point{r, t}), c.Add(raster.Point{s, s}))
		z.Add2(c.Add(raster.Point{t, r}), c.Add(raster.Point{0, r}))
		// Add another quadratic segment whose angle ranges between 0 and 90 degrees.
		// For an explanation of the magic constants 22, 150, 181 and 256, read the
		// comments in the freetype/raster package.
		dot := 256 * d.Dot(raster.Point{0, r}) / (r * r)
		multiple := raster.Fix32(150 - 22*(dot-181)/(256-181))
		z.Add2(c.Add(raster.Point{dx, r + dy}.Mul(multiple)), c.Add(d))
		// Close the curve.
		z.Add1(c)
	}
	z.Rasterize(mp)

	for i := 0; i < n; i++ {
		cx := raster.Fix32(25600 + 51200*(i%4))
		cy := raster.Fix32(2560 + 32000*(i/4))
		for j := 0; j < n; j++ {
			theta := math.Pi * float64(j) / (n - 1)
			dx := raster.Fix32(r * math.Cos(theta))
			dy := raster.Fix32(r * math.Sin(theta))
			m.Set(int((cx+dx)/256), int((cy+dy)/256), color.RGBA{255, 255, 0, 255})
		}
	}

	// Save that RGBA image to disk.
	f, err := os.Create("out.png")
	if err != nil {
		log.Println(err)
		os.Exit(1)
	}
	defer f.Close()
	b := bufio.NewWriter(f)
	err = png.Encode(b, m)
	if err != nil {
		log.Println(err)
		os.Exit(1)
	}
	err = b.Flush()
	if err != nil {
		log.Println(err)
		os.Exit(1)
	}
	fmt.Println("Wrote out.png OK.")
}