Golang Font.Bounds方法代碼示例

func generateAtlas(font *truetype.Font, scale int32, dpi float64, width, height float32) ([]Vector4, *image.RGBA, []float32) {
	var low rune = 32
	var high rune = 127
	glyphCount := int32(high - low + 1)
	offsets := make([]float32, glyphCount)

	bounds := font.Bounds(scale)
	gw := float32(bounds.XMax - bounds.XMin)
	gh := float32(bounds.YMax - bounds.YMin)
	imageWidth := glh.Pow2(uint32(gw * float32(glyphCount)))
	imageHeight := glh.Pow2(uint32(gh))
	imageBounds := image.Rect(0, 0, int(imageWidth), int(imageHeight))
	sx := float32(2) / width
	sy := float32(2) / height
	w := gw * sx
	h := gh * sy
	img := image.NewRGBA(imageBounds)
	c := freetype.NewContext()
	c.SetDst(img)
	c.SetClip(img.Bounds())
	c.SetSrc(image.White)
	c.SetDPI(dpi)
	c.SetFontSize(float64(scale))
	c.SetFont(font)

	var gi int32
	var gx, gy float32
	verts := make([]Vector4, 0)
	texWidth := float32(img.Bounds().Dx())
	texHeight := float32(img.Bounds().Dy())

	for ch := low; ch <= high; ch++ {
		index := font.Index(ch)
		metric := font.HMetric(scale, index)

		//the offset is used when drawing a string of glyphs - we will advance a glyph's quad by the width of all previous glyphs in the string
		offsets[gi] = float32(metric.AdvanceWidth) * sx

		//draw the glyph into the atlas at the correct location
		pt := freetype.Pt(int(gx), int(gy)+int(c.PointToFix32(float64(scale))>>8))
		c.DrawString(string(ch), pt)

		tx1 := gx / texWidth
		ty1 := gy / texHeight
		tx2 := (gx + gw) / texWidth
		ty2 := (gy + gh) / texHeight

		//the x,y coordinates are the same for each quad; only the texture coordinates (stored in z,w) change.
		//an optimization would be to only store texture coords, but I haven't figured that out yet
		verts = append(verts, Vector4{-1, 1, tx1, ty1},
			Vector4{-1 + (w), 1, tx2, ty1},
			Vector4{-1, 1 - (h), tx1, ty2},
			Vector4{-1 + (w), 1 - (h), tx2, ty2})

		gx += gw
		gi++
	}
	return verts, img, offsets
}

// Extents returns the FontExtents for a font.
// TODO needs to read this https://developer.apple.com/fonts/TrueType-Reference-Manual/RM02/Chap2.html#intro
func Extents(font *truetype.Font, size float64) FontExtents {
	bounds := font.Bounds(font.FUnitsPerEm())
	scale := size / float64(font.FUnitsPerEm())
	return FontExtents{
		Ascent:  float64(bounds.YMax) * scale,
		Descent: float64(bounds.YMin) * scale,
		Height:  float64(bounds.YMax-bounds.YMin) * scale,
	}
}

func ExpectedSize(font *truetype.Font, s string) (int32, int32, error) {

	c := freetype.NewContext()
	c.SetDPI(dpi)
	c.SetFont(font)
	c.SetFontSize(size)

	scale := size / float64(font.FUnitsPerEm())

	prev := font.Index(rune(s[0]))
	width := int32(font.HMetric(font.FUnitsPerEm(), prev).AdvanceWidth)
	for _, char := range s[1:] {
		index := font.Index(char)
		width += int32(font.Kerning(font.FUnitsPerEm(), prev, index) +
			font.HMetric(font.FUnitsPerEm(), index).AdvanceWidth)
		prev = index
	}
	width = int32(float64(width) * scale)

	bounds := font.Bounds(font.FUnitsPerEm())
	height := int32(float64(bounds.YMax-bounds.YMin) * scale)

	return width, height, nil
}

func genGlyphs(font *truetype.Font, size int, text string) (glyphs []*glyph) {

	scale := int32(float64(size) * dpi * (64.0 / 72.0))
	clip := image.Rect(0, 0, width, height)

	// Calculate the rasterizer's bounds to handle the largest glyph.
	b := font.Bounds(scale)
	xmin := int(b.XMin) >> 6
	ymin := -int(b.YMax) >> 6
	xmax := int(b.XMax+63) >> 6
	ymax := -int(b.YMin-63) >> 6

	r := raster.NewRasterizer(xmax-xmin, ymax-ymin)
	buf := truetype.NewGlyphBuf()

	for _, variant := range []string{strings.ToUpper(text), strings.ToLower(text)} {

		pt := Pt(30, 10+int(pointToFix32(float64(size))>>8))

		for _, char := range variant {

			idx := font.Index(char)
			buf.Load(font, scale, idx, truetype.FullHinting)

			// Calculate the integer-pixel bounds for the glyph.
			xmin := int(raster.Fix32(buf.B.XMin<<2)) >> 8
			ymin := int(-raster.Fix32(buf.B.YMax<<2)) >> 8
			xmax := int(raster.Fix32(buf.B.XMax<<2)+0xff) >> 8
			ymax := int(-raster.Fix32(buf.B.YMin<<2)+0xff) >> 8
			fx := raster.Fix32(-xmin << 8)
			fy := raster.Fix32(-ymin << 8)

			ix := int(pt.X >> 8)
			iy := int(pt.Y >> 8)

			// Rasterize the glyph's vectors.
			r.Clear()
			e0 := 0
			for _, e1 := range buf.End {
				drawContour(r, buf.Point[e0:e1], fx, fy)
				e0 = e1
			}

			mask := image.NewAlpha(image.Rect(0, 0, xmax-xmin, ymax-ymin))
			r.Rasterize(raster.NewAlphaSrcPainter(mask))
			pt.X += raster.Fix32(buf.AdvanceWidth << 2)
			offset := image.Point{xmin + ix, ymin + iy}

			glyphRect := mask.Bounds().Add(offset)
			dr := clip.Intersect(glyphRect)
			mp := image.Point{0, dr.Min.Y - glyphRect.Min.Y}
			glyphs = append(glyphs, &glyph{
				mask: mask,
				mp:   mp,
				dr:   dr,
			})

		}
	}

	return

}