Golang freetype.NewContext函數代碼示例

func renderMeme(ctx appengine.Context, w io.Writer, id, topText, botText string) error {
	// Read template.
	templateName := templateFile(id)
	reader, err := file.Open(ctx, gcsFilesApiPath(bucket, templateName))
	if err != nil {
		return err
	}
	defer reader.Close()

	bgImg, err := jpeg.Decode(reader)
	if err != nil {
		return err
	}

	img := image.NewRGBA(bgImg.Bounds())
	draw.Draw(img, bgImg.Bounds(), bgImg, image.ZP, draw.Src)

	c := freetype.NewContext()
	c.SetDPI(72)
	c.SetFont(font)
	c.SetClip(img.Bounds())
	c.SetDst(img)
	c.SetHinting(freetype.FullHinting)

	drawFitCentered(c, topText, img, false)
	drawFitCentered(c, botText, img, true)

	err = jpeg.Encode(w, img, &jpeg.Options{Quality: 75})
	if err != nil {
		return err
	}

	return nil
}

func (a *Annotator) init() error {

	// load the font
	fontBytes, err := resources.Asset(fontfile)
	if err != nil {
		return err
	}

	font, err := freetype.ParseFont(fontBytes)
	if err != nil {
		return err
	}

	// Initialize the context.
	fg := image.White

	a.context = freetype.NewContext()
	a.context.SetDPI(dpi)
	a.context.SetFont(font)
	a.context.SetFontSize(size)

	a.context.SetClip(a.image.Bounds())
	a.context.SetDst(a.image)
	a.context.SetSrc(fg)

	switch hinting {
	default:
		a.context.SetHinting(freetype.NoHinting)
	case "full":
		a.context.SetHinting(freetype.FullHinting)
	}

	return nil
}

// textBox renders t into a tight fitting image
func (ig *ImageGraphics) textBox(t string, size int) image.Image {
	// Initialize the context.
	fg := image.NewUniform(color.Alpha{0xff})
	bg := image.NewUniform(color.Alpha{0x00})
	canvas := image.NewAlpha(image.Rect(0, 0, 400, 2*size))
	draw.Draw(canvas, canvas.Bounds(), bg, image.ZP, draw.Src)

	c := freetype.NewContext()
	c.SetDPI(dpi)
	c.SetFont(ig.font)
	c.SetFontSize(float64(size))
	c.SetClip(canvas.Bounds())
	c.SetDst(canvas)
	c.SetSrc(fg)

	// Draw the text.
	h := c.FUnitToPixelRU(ig.font.UnitsPerEm())
	pt := freetype.Pt(0, h)
	extent, err := c.DrawString(t, pt)
	if err != nil {
		log.Println(err)
		return nil
	}
	// log.Printf("text %q, extent: %v", t, extent)
	return canvas.SubImage(image.Rect(0, 0, int(extent.X/256), h*5/4))
}

/**
 * Create a new Graphic context from an image
 */
func NewGraphicContext(img draw.Image) *ImageGraphicContext {
	var painter Painter
	switch selectImage := img.(type) {
	case *image.RGBA:
		painter = raster.NewRGBAPainter(selectImage)
	//case *image.NRGBA:
	//	painter = NewNRGBAPainter(selectImage)
	default:
		panic("Image type not supported")
	}
	width, height := img.Bounds().Dx(), img.Bounds().Dy()
	dpi := 92
	ftContext := freetype.NewContext()
	ftContext.SetDPI(dpi)
	ftContext.SetClip(img.Bounds())
	ftContext.SetDst(img)
	gc := &ImageGraphicContext{
		NewStackGraphicContext(),
		img,
		painter,
		raster.NewRasterizer(width, height),
		raster.NewRasterizer(width, height),
		ftContext,
		dpi,
	}
	return gc
}

// textBox renders t into a tight fitting image
func (ig *ImageGraphics) textBox(t string, font chart.Font) image.Image {
	// Initialize the context.
	fg := image.NewUniform(color.Alpha{0xff})
	bg := image.NewUniform(color.Alpha{0x00})
	width := ig.TextLen(t, font)
	size := ig.relFontsizeToPixel(font.Size)
	canvas := image.NewAlpha(image.Rect(0, 0, width, int(1.5*size+0.5)))
	draw.Draw(canvas, canvas.Bounds(), bg, image.ZP, draw.Src)

	c := freetype.NewContext()
	c.SetDPI(dpi)
	c.SetFont(ig.font)
	c.SetFontSize(size)
	c.SetClip(canvas.Bounds())
	c.SetDst(canvas)
	c.SetSrc(fg)

	// Draw the text.
	h := c.FUnitToPixelRU(ig.font.UnitsPerEm())
	pt := freetype.Pt(0, h)
	extent, err := c.DrawString(t, pt)
	if err != nil {
		log.Println(err)
		return nil
	}
	// log.Printf("text %q, extent: %v", t, extent)
	return canvas.SubImage(image.Rect(0, 0, int((extent.X+127)/256), h*5/4))
}

func (q *Quote) TextToImage() *image.RGBA {
	spacing := 1.5
	var fontsize float64 = 8

	// read font
	fontBytes, err := ioutil.ReadFile(os.Getenv("FONT_FILE"))
	checkErr(err)
	font, err := freetype.ParseFont(fontBytes)
	checkErr(err)

	// Initialize the context.
	fg, bg := image.White, image.Transparent

	// 755px by 378px is the size Vox uses
	rgba := image.NewRGBA(image.Rect(0, 0, 755, 378))
	draw.Draw(rgba, rgba.Bounds(), bg, image.ZP, draw.Src)
	c := freetype.NewContext()
	c.SetDPI(300)
	c.SetFont(font)
	c.SetFontSize(fontsize)
	c.SetClip(rgba.Bounds())
	c.SetDst(rgba)
	c.SetSrc(fg)

	// Draw the text
	pt := freetype.Pt(50, 50+int(c.PointToFix32(fontsize)>>8))
	lines := strings.Split(q.Text, "\n")
	for _, s := range lines {
		_, err = c.DrawString(s, pt)
		checkErr(err)
		pt.Y += c.PointToFix32(fontsize * spacing)
	}

	return rgba
}

// NewText creates a new Text object. The x and y positions represent the left
// and bottom of text without tails.
func NewText(x, y float64, font *Font, fontSize float64, message string) (*Text, error) {

	text := &Text{}

	text.x = x
	text.y = y - fontSize

	text.fontColor = image.NewUniform(color.RGBA{0, 0, 0, 255})

	text.context = freetype.NewContext()
	text.context.SetDPI(dpi)
	text.context.SetFont(font.font)
	text.context.SetFontSize(fontSize)
	text.context.SetSrc(text.fontColor)
	text.context.SetHinting(freetype.FullHinting)

	text.fontSize = fontSize

	err := text.SetMessage(message)
	if err != nil {
		return text, err
	}

	return text, nil
}

// 畫一個帶有text的圖片
func (this *Signer) drawStringImage(text string) (image.Image, error) {
	fg, bg := image.Black, image.Transparent
	rgba := image.NewRGBA(image.Rect(0, 0, this.signPoint.X, this.signPoint.Y))
	draw.Draw(rgba, rgba.Bounds(), bg, image.ZP, draw.Src)

	c := freetype.NewContext()
	c.SetDPI(this.Dpi)
	c.SetFont(this.font)
	c.SetFontSize(this.FontSize)
	c.SetClip(rgba.Bounds())
	c.SetDst(rgba)
	c.SetSrc(fg)

	// Draw the text.
	pt := freetype.Pt(10, 10+int(c.PointToFix32(12)>>8))
	for _, s := range strings.Split(text, "\r\n") {
		_, err := c.DrawString(s, pt)
		if err != nil {
			glog.Errorf("c.DrawString(%s) error(%v)", s, err)
			return nil, err
		}
		pt.Y += c.PointToFix32(12 * 1.5)
	}

	// fff, _ := os.Create("aaa.png")
	// defer fff.Close()
	// png.Encode(fff, rgba)

	return rgba, nil
}

func getFont(path string, sizePts int) font {
	sizePx := int(float64(sizePts)/ptInch*pxInch + 0.5)

	if f, ok := fonts[path]; ok {
		f.size = sizePx
		return f
	}

	in, err := os.Open(path)
	if err != nil {
		panic(err)
	}
	defer in.Close()

	fdata, err := ioutil.ReadAll(in)
	if err != nil {
		panic(err)
	}

	f := font{
		path:    path,
		Context: freetype.NewContext(),
	}
	if f.Font, err = truetype.Parse(fdata); err != nil {
		panic(err)
	}
	f.SetFont(f.Font)
	f.SetDPI(pxInch)
	fonts[path] = f

	f.size = sizePx
	return f
}

func nosuchtile(v ...interface{}) []byte {
	im := image.NewRGBA(image.Rect(0, 0, tilesize, tilesize))
	col := color.RGBA{255, 0, 0, 255}
	for i := 0; i < tilesize; i++ {
		im.Set(i, 0, col)
		im.Set(i, tilesize-1, col)
		im.Set(0, i, col)
		im.Set(tilesize-1, i, col)
	}
	ctx := freetype.NewContext()
	ctx.SetDPI(72)
	ctx.SetFont(nstfont)
	ctx.SetFontSize(16)
	ctx.SetClip(im.Bounds())
	ctx.SetDst(im)
	ctx.SetSrc(image.Black)
	for i, n := range v {
		_, err := ctx.DrawString(fmt.Sprint(n), freetype.Pt(30, 30+i*20))
		if err != nil {
			fmt.Println(err)
		}
	}
	var buf bytes.Buffer
	err := png.Encode(&buf, im)
	if err != nil {
		fmt.Println(err)
	}
	return buf.Bytes()
}

// 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
}

// 畫一個帶有text的圖片
func drawStringImage(text string, fontFile string) image.Image {
	fontBytes, err := ioutil.ReadFile(fontFile)
	if err != nil {
		log.Fatalln(err)
	}

	font, err := freetype.ParseFont(fontBytes)
	if err != nil {
		log.Fatalln(err)
	}

	fg, bg := image.Black, image.White
	rgba := image.NewRGBA(image.Rect(0, 0, 640, 480))
	draw.Draw(rgba, rgba.Bounds(), bg, image.ZP, draw.Src)

	c := freetype.NewContext()
	c.SetDPI(72)
	c.SetFont(font)
	c.SetFontSize(12)
	c.SetClip(rgba.Bounds())
	c.SetDst(rgba)
	c.SetSrc(fg)

	// Draw the text.
	pt := freetype.Pt(10, 10+int(c.PointToFix32(12)>>8))
	for _, s := range strings.Split(text, "\r\n") {
		_, err = c.DrawString(s, pt)
		pt.Y += c.PointToFix32(12 * 1.5)
	}

	return rgba
}

/*
生成驗證碼
bg:背景色
fg:前景色
length:字符長度
width:寬度
height:高度
size:字體大小
fontPath:字體文件路徑
*/
func GenerateCaptcha(bg, fg *image.Uniform, length int, width int, height int, size float64, fontPath string) *Captcha {
	fontBytes, err := ioutil.ReadFile(fontPath)
	if err != nil {
		panic(err)
	}
	font, err := truetype.Parse(fontBytes)

	if err != nil {
		panic(err)
	}
	cap := &Captcha{}
	cap.Text = randString(length)
	cap.Image = image.NewRGBA(image.Rect(0, 0, width, height))
	draw.Draw(cap.Image, cap.Image.Bounds(), bg, image.ZP, draw.Src)
	c := freetype.NewContext()
	c.SetFont(font)
	c.SetFontSize(size)
	c.SetClip(cap.Image.Bounds())
	c.SetDst(cap.Image)
	c.SetSrc(fg)
	pt := freetype.Pt(0, int(c.PointToFix32(size)>>8))
	for _, s := range cap.Text {
		_, err = c.DrawString(string(s), pt)
		if err != nil {
			panic(err)
			return nil
		}
		pt.X += c.PointToFix32(size * 0.5)
	}
	return cap
}

// Color in HEX format: FAFAFA
func (g *Gummy) DrawText(text, textColor string, fontSize, xPosition, yPosition int) error {

	// Get black or white depending on the background
	if textColor == "" {
		c := (*g.Color).(color.RGBA)
		if blackWithBackground(float64(c.R), float64(c.G), float64(c.B)) {
			textColor = "000000"
		} else {
			textColor = "FFFFFF"
		}
	}

	fc := freetype.NewContext()
	fc.SetDst(g.Img)
	fc.SetFont(g.Font)
	fc.SetClip(g.Img.Bounds())

	// Color parsing
	cr, _ := strconv.ParseUint(string(textColor[:2]), 16, 64)
	cg, _ := strconv.ParseUint(string(textColor[2:4]), 16, 64)
	cb, _ := strconv.ParseUint(string(textColor[4:]), 16, 64)
	c := image.NewUniform(color.RGBA{R: uint8(cr), G: uint8(cg), B: uint8(cb), A: 255})

	fc.SetSrc(c)
	fc.SetFontSize(float64(fontSize))

	_, err := fc.DrawString(text, freetype.Pt(xPosition, yPosition))

	return err
}

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
}