Golang openvg.Start函數代碼示例

// imgtest draws images at the corners and center
func imagetest(w, h int) {
	openvg.Start(w, h)
	imgw := 422
	imgh := 238
	fiw := openvg.VGfloat(imgw)
	fih := openvg.VGfloat(imgh)
	fw := openvg.VGfloat(w)
	fh := openvg.VGfloat(h)
	vgzero := openvg.VGfloat(0.0)
	cx := (fw / 2) - (fiw / 2)
	cy := (fh / 2) - (fih / 2)
	ulx := vgzero
	uly := fh - fih
	urx := fw - fiw
	ury := uly
	llx := vgzero
	lly := vgzero
	lrx := urx
	lry := lly
	openvg.Start(w, h)
	openvg.Background(0, 0, 0)
	openvg.Image(cx, cy, imgw, imgh, "desert1.jpg")
	openvg.Image(ulx, uly, imgw, imgh, "desert2.jpg")
	openvg.Image(urx, ury, imgw, imgh, "desert3.jpg")
	openvg.Image(llx, lly, imgw, imgh, "desert4.jpg")
	openvg.Image(lrx, lry, imgw, imgh, "desert5.jpg")
	openvg.End()
}

func main() {
	var color string
	openvg.Start(width, height)
	openvg.Background(200, 200, 200)
	for i := 0; i < niter; i++ {
		x := random(0, width)
		y := random(height/3, (height*2)/3)
		r := random(0, 10000)
		switch {
		case r >= 0 && r <= 2500:
			color = "white"
		case r > 2500 && r <= 5000:
			color = "maroon"
		case r > 5000 && r <= 7500:
			color = "gray"
		case r > 7500 && r <= 10000:
			color = "black"
		}
		openvg.FillColor(color, openvg.VGfloat(opacity))
		openvg.Circle(openvg.VGfloat(x), openvg.VGfloat(y), openvg.VGfloat(size))
	}
	openvg.End()
	bufio.NewReader(os.Stdin).ReadByte()
	openvg.Finish()
}

// tb draws a block of text
func tb(w, h int) {
	para := []string{
		"For lo,",
		"the winter is past,",
		"the rain is over and gone",
		"the flowers appear on the earth;",
		"the time for the singing of birds is come,",
		"and the voice of the turtle is heard in our land",
	}

	tmargin := openvg.VGfloat(w) * 0.50
	lmargin := openvg.VGfloat(w) * 0.10
	top := openvg.VGfloat(h) * .9
	mid := openvg.VGfloat(h) * .6
	bot := openvg.VGfloat(h) * .3

	fontsize := 24
	leading := openvg.VGfloat(40.0)
	lfontsize := fontsize * 2
	midb := ((leading * 2) + (leading / 2)) - openvg.VGfloat(lfontsize/2)

	openvg.Start(w, h)
	openvg.FillRGB(49, 79, 79, 1)
	textlines(tmargin, top, para, "serif", fontsize, leading)
	textlines(tmargin, mid, para, "sans", fontsize, leading)
	textlines(tmargin, bot, para, "mono", fontsize, leading)
	openvg.Text(lmargin, top-midb, "Serif", "sans", lfontsize)
	openvg.Text(lmargin, mid-midb, "Sans", "sans", lfontsize)
	openvg.Text(lmargin, bot-midb, "Mono", "sans", lfontsize)
	openvg.End()
}

// rshapes draws shapes with random colors, openvg.Strokes, and sizes.
func rshapes(width, height, n int) {

	var sx, sy, cx, cy, px, py, ex, ey, pox, poy openvg.VGfloat

	np := 10
	polyx := make([]openvg.VGfloat, np)
	polyy := make([]openvg.VGfloat, np)
	openvg.Start(width, height)
	for i := 0; i < n; i++ {
		openvg.FillRGB(randcolor(), randcolor(), randcolor(), openvg.VGfloat(rand.Float32()))
		openvg.Ellipse(randf(width), randf(height), randf(200), randf(100))
		openvg.Circle(randf(width), randf(height), randf(100))
		openvg.Rect(randf(width), randf(height), randf(200), randf(100))
		openvg.Arc(randf(width), randf(height), randf(200), randf(200), randf(360), randf(360))

		sx = randf(width)
		sy = randf(height)
		openvg.StrokeRGB(randcolor(), randcolor(), randcolor(), 1)
		openvg.StrokeWidth(randf(5))
		openvg.Line(sx, sy, sx+randf(200), sy+randf(100))
		openvg.StrokeWidth(0)

		sx = randf(width)
		sy = randf(height)
		ex = sx + randf(200)
		ey = sy
		cx = sx + ((ex - sx) / 2.0)
		cy = sy + randf(100)
		openvg.Qbezier(sx, sy, cx, cy, ex, ey)

		sx = randf(width)
		sy = randf(height)
		ex = sx + randf(200)
		ey = sy
		cx = sx + ((ex - sx) / 2.0)
		cy = sy + randf(100)
		px = cx
		py = sy - randf(100)
		openvg.Cbezier(sx, sy, cx, cy, px, py, ex, ey)

		pox = randf(width)
		poy = randf(height)
		for j := 0; j < np; j++ {
			polyx[j] = pox + randf(200)
			polyy[j] = poy + randf(100)
		}
		openvg.Polygon(polyx, polyy) // , np)

		pox = randf(width)
		poy = randf(height)
		for j := 0; j < np; j++ {
			polyx[j] = pox + randf(200)
			polyy[j] = poy + randf(100)
		}
		openvg.Polyline(polyx, polyy) // , np)
	}
	openvg.FillRGB(128, 0, 0, 1)
	openvg.Text(20, 20, "OpenVG on the Raspberry Pi", "sans", 32)
	openvg.End()
}

func main() {
	var cx, cy, cw, ch, midy int
	message := "Now is the time for all good men to come to the aid of the party"

	w, h := openvg.Init()
	var speed openvg.VGfloat = 0.5
	var x openvg.VGfloat = 0
	midy = (h / 2)
	fontsize := w / 50
	cx = 0
	ch = fontsize * 2
	cw = w
	cy = midy - (ch / 2)

	rx, ry, rw, rh := openvg.VGfloat(cx), openvg.VGfloat(cy), openvg.VGfloat(cw), openvg.VGfloat(ch)
	// scroll the text, only in the clipping rectangle
	for x = 0; x < rw+speed; x += speed {
		openvg.Start(w, h)
		openvg.Background(255, 255, 255)
		openvg.FillRGB(0, 0, 0, .2)
		openvg.Rect(rx, ry, rw, rh)
		openvg.ClipRect(cx, cy, cw, ch)
		openvg.Translate(x, ry+openvg.VGfloat(fontsize/2))
		openvg.FillRGB(0, 0, 0, 1)
		openvg.Text(0, 0, message, "sans", fontsize)
		openvg.ClipEnd()
		openvg.End()
	}
	bufio.NewReader(os.Stdin).ReadBytes('\n')
	openvg.Finish()
	os.Exit(0)
}

// loadimage loads all the images of the deck into a map for later display
func loadimage(d deck.Deck, m map[string]image.Image) {
	firstrun++
	w, h := d.Canvas.Width, d.Canvas.Height
	cw := openvg.VGfloat(w)
	ch := openvg.VGfloat(h)
	msize := int(cw * .01)
	mx := cw / 2
	my := ch * 0.05
	mbg := "white"
	mfg := "black"
	for ns, s := range d.Slide {
		for ni, i := range s.Image {
			if !modfile(i.Name, StartTime) {
				continue
			}
			openvg.Start(w, h)
			if i.Link != "" {
				fmt.Fprintf(os.Stderr, "Found altimg %s\n", i.Link)
			}
			f, err := os.Open(i.Name)
			if err != nil {
				fmt.Fprintf(os.Stderr, "%v\n", err)
				continue
			}
			img, _, err := image.Decode(f)
			if err != nil {
				fmt.Fprintf(os.Stderr, "%v\n", err)
				continue
			}
			openvg.FillColor(mbg)
			openvg.Rect(0, 0, cw, ch)
			openvg.FillColor(mfg)
			openvg.TextMid(mx, my, fmt.Sprintf("Loading image %s %d from slide %d", i.Name, ni, ns), "sans", msize)
			bounds := img.Bounds()
			iw := i.Width
			ih := i.Height
			if i.Scale > 0 {
				iw = int(float64(iw) * (i.Scale / 100))
				ih = int(float64(ih) * (i.Scale / 100))
			}
			// if the specified dimensions are native use those, otherwise resize
			if iw == (bounds.Max.X-bounds.Min.X) && ih == (bounds.Max.Y-bounds.Min.Y) {
				m[i.Name] = img
			} else {
				g := gift.New(gift.Resize(iw, ih, gift.BoxResampling))
				resized := image.NewRGBA(g.Bounds(img.Bounds()))
				g.Draw(resized, img)
				m[i.Name] = resized
			}
			f.Close()
			openvg.End()
		}
	}
}

// raspberry pi, scaled to the screen dimensions
func raspi(w, h int, s string) {
	midx := openvg.VGfloat(w) / 2
	midy := openvg.VGfloat(h) / 2
	rw := midx
	rh := (rw * 2) / 3
	fontsize := w / 25
	openvg.Start(w, h)
	openvg.Background(255, 255, 255)
	makepi(midx-(rw/2), midy-(rh/2), rw, rh)
	openvg.FillRGB(128, 0, 0, 1)
	openvg.TextMid(midx, midy-(rh/2)-openvg.VGfloat(fontsize*2), s, "sans", fontsize)
	openvg.End()
}

//planets is an exploration of scale
func planets(width, height int, message string) {

	w := openvg.VGfloat(width)
	h := openvg.VGfloat(height)
	y := h / 2

	margin := openvg.VGfloat(100.0)
	minsize := openvg.VGfloat(7.0)
	labeloc := openvg.VGfloat(100.0)
	bgcolor := "black"
	labelcolor := "white"
	maxsize := (h / 2) * 0.05

	origin := sun.distance
	mostDistant := neptune.distance
	firstSize := mercury.radius
	lastSize := neptune.radius

	openvg.Start(width, height)
	openvg.BackgroundColor(bgcolor)

	for _, p := range solarSystem {
		x := vmap(p.distance, origin, mostDistant, margin, w-margin)
		r := vmap(p.radius, firstSize, lastSize, minsize, maxsize)

		if p.name == "Sun" {
			openvg.FillRGB(p.color.Red, p.color.Green, p.color.Blue, 1)
			openvg.Circle(margin-(r/2), y, r)
		} else {
			light(x, y, r, p.color)
			openvg.Circle(x, y, r)
			if p.name == "Saturn" {
				ringwidth := r * 2.35 // Saturn's rings are over 2x the planet radius
				openvg.StrokeWidth(3)
				openvg.StrokeRGB(p.color.Red, p.color.Green, p.color.Blue, 1)
				openvg.Line((x - ringwidth/2), y, (x + ringwidth/2), y)
				openvg.StrokeWidth(0)
			}
		}
		if p.name == "Earth" && len(message) > 1 {
			openvg.StrokeColor(labelcolor)
			openvg.StrokeWidth(1)
			openvg.Line(x, y+(r/2), x, y+labeloc)
			openvg.StrokeWidth(0)
			openvg.FillColor(labelcolor)
			openvg.TextMid(x, y+labeloc+10, message, "sans", 12)
		}
	}
	openvg.End()
}

// raspberry pi, scaled to the screen dimensions
func main() {
	w, h := openvg.Init()
	midx := openvg.VGfloat(w) / 2
	midy := openvg.VGfloat(h) / 2
	rw := midx
	rh := (rw * 2) / 3
	fontsize := w / 25
	openvg.Start(w, h)
	openvg.Background(255, 255, 255)
	makepi(midx-(rw/2), midy-(rh/2), rw, rh)
	makepi(200, 100, 75, 50)
	openvg.FillRGB(128, 0, 0, 1)
	openvg.TextMid(midx, midy-(rh/2)-openvg.VGfloat(fontsize*2), "The Raspberry Pi", "sans", fontsize)
	WaitEnd()
}

func main() {

	width, height := openvg.Init()

	w := openvg.VGfloat(width)
	h := openvg.VGfloat(height)
	y := h / 2
	var (
		margin  openvg.VGfloat = 100.0
		minsize openvg.VGfloat = 7.0
		labeloc openvg.VGfloat = 100.0
	)
	bgcolor := "black"
	labelcolor := "white"
	maxsize := (h / 2) * 0.05

	origin := sun.distance
	mostDistant := neptune.distance
	firstSize := mercury.radius
	lastSize := neptune.radius

	openvg.Start(width, height)
	openvg.BackgroundColor(bgcolor)

	for _, p := range solarSystem {
		x := vmap(p.distance, origin, mostDistant, margin, w-margin)
		r := vmap(p.radius, firstSize, lastSize, minsize, maxsize)

		if p.name == "Sun" {
			openvg.FillRGB(p.color.Red, p.color.Green, p.color.Blue, 1)
			openvg.Circle(margin-(r/2), y, r)
		} else {
			light(x, y, r, p.color)
			openvg.Circle(x, y, r)
		}
		if p.name == "Earth" && len(os.Args) > 1 {
			openvg.StrokeColor(labelcolor)
			openvg.StrokeWidth(1)
			openvg.Line(x, y+(r/2), x, y+labeloc)
			openvg.StrokeWidth(0)
			openvg.FillColor(labelcolor)
			openvg.TextMid(x, y+labeloc+10, os.Args[1], "sans", 12)
		}
	}
	openvg.End()
	bufio.NewReader(os.Stdin).ReadByte()
	openvg.Finish()
}

func main() {
	width, height := openvg.Init() // OpenGL, etc initialization

	w2 := openvg.VGfloat(width / 2)
	h2 := openvg.VGfloat(height / 2)
	w := openvg.VGfloat(width)

	openvg.Start(width, height)                               // Start the picture
	openvg.BackgroundColor("black")                           // Black background
	openvg.FillRGB(44, 100, 232, 1)                           // Big blue marble
	openvg.Circle(w2, 0, w)                                   // The "world"
	openvg.FillColor("white")                                 // White text
	openvg.TextMid(w2, h2, "hello, world", "serif", width/10) // Greetings
	openvg.End()                                              // End the picture
	bufio.NewReader(os.Stdin).ReadBytes('\n')                 // Pause until [RETURN]
	openvg.Finish()                                           // Graphics cleanup
}

func gradient(width, height int) {
	w := openvg.VGfloat(width)
	h := openvg.VGfloat(height)
	stops := []openvg.Offcolor{
		{0.0, openvg.RGB{255, 255, 255}, 1.0},
		{0.5, openvg.RGB{128, 128, 128}, 1.0},
		{1.0, openvg.RGB{0, 0, 0}, 1.0},
	}

	x1 := w / 8
	x2 := (w * 3) / 8
	y1 := h / 3
	y2 := (h * 2) / 3
	cx := (w * 3) / 4
	cy := (h / 2)
	r := (x2 - x1)
	fx := cx + (r / 4)
	fy := cy + (r / 4)
	openvg.Start(width, height)
	openvg.BackgroundRGB(128, 128, 128, 1)
	openvg.FillLinearGradient(x1, y1, x2, y2, stops)
	openvg.Rect(x1, y1, x2-x1, y2-y1)
	openvg.FillRadialGradient(cx, cy, fx, fy, r, stops)
	openvg.Circle(cx, cy, r)

	openvg.FillRGB(0, 0, 0, 0.3)
	openvg.Circle(x1, y1, 10)
	openvg.Circle(x2, y2, 10)
	openvg.Circle(cx, cy, 10)
	openvg.Circle(cx+r/2, cy, 10)
	openvg.Circle(fx, fy, 10)

	openvg.FillColor("black")
	SansTypeface := "sans"
	openvg.TextMid(x1, y1-20, "(x1, y1)", SansTypeface, 18)
	openvg.TextMid(x2, y2+10, "(x2, y2)", SansTypeface, 18)
	openvg.TextMid(cx, cy, "(cx, cy)", SansTypeface, 18)
	openvg.TextMid(fx, fy, "(fx, fy)", SansTypeface, 18)
	openvg.TextEnd(cx+(r/2)+20, cy, "r", SansTypeface, 18)

	openvg.TextMid(x1+((x2-x1)/2), h/6, "Linear Gradient", SansTypeface, 36)
	openvg.TextMid(cx, h/6, "Radial Gradient", SansTypeface, 36)
	openvg.End()
}

func main() {
	setOptions()
	rand.Seed(time.Now().Unix())
	w, h := openvg.Init()
	width, height := openvg.VGfloat(w), openvg.VGfloat(h)
	initParticles(width, height)
	openvg.Start(w, h)
	i := 0
	for {
		draw(width, height)
		time.Sleep(2 * time.Millisecond)
		//fmt.Printf(".")
		i++
		if alternate && i == nswitch { // switch launch direction every nswitch draws
			directionRTL = !directionRTL
			i = 0
		}
	}
}

// textplay exercises text functions
func textplay(w, h int) {
	forlo := `For lo, the winter is past, the rain is over and gone. The flowers appear on the earth, the time for the singing of birds is come, and the voice of the turtle is heard in our land.`

	// forsince := `For since by man came death, by man came also the resurrection of the dead, for as in Adam all die, even so in Christ shall all be made alive.`

	openvg.Start(w, h)
	var (
		tw     openvg.VGfloat = 300
		begin  openvg.VGfloat = 50
		xincr  openvg.VGfloat = 400
		offset openvg.VGfloat = 100
	)
	for x, y := begin, openvg.VGfloat(h)-offset; x < openvg.VGfloat(w/2); x += xincr {
		textwrap(x, y, tw, forlo, "sans", 12, 24, 0.25, "black")
		textwrap(x, y-400, tw, forlo, "sans", 12, 24, 0.5, "black")
		tw -= offset
	}
	openvg.End()
}

func main() {
	var loop = flag.Bool("loop", false, "Loop the show")
	var resize = flag.Bool("resize", false, `Resize image to fit the screen.`)
	var bgcolor = flag.String("bg", "black", `Background color (named color or rgb(r,g,b)).`)
	var delay = flag.Duration("delay", 2*time.Second, "Delay between pictures")
	flag.Usage = func() {
		fmt.Fprintf(os.Stderr, "usage: %s [ flags ] images...\n", os.Args[0])
		flag.PrintDefaults()
		os.Exit(1)
	}

	flag.Parse()
	w, h := openvg.Init()
	images := []image.Image{}
	imgcount := 0
	for _, imgfile := range flag.Args() {
		fmt.Fprintf(os.Stderr, "loading %q ", imgfile)
		img, err := getimage(imgfile, w, h, *resize)
		if err != nil {
			fmt.Fprintln(os.Stderr, err)
			continue
		}
		images = append(images, img)
		imgcount++
		fmt.Fprintln(os.Stderr, "ok")
	}
	for {
		for _, img := range images {
			ib := img.Bounds()
			imw, imh := ib.Max.X-ib.Min.X, ib.Max.Y-ib.Min.Y
			openvg.Start(w, h)
			openvg.BackgroundColor(*bgcolor)
			x, y := openvg.VGfloat(w)/2-openvg.VGfloat(imw)/2, openvg.VGfloat(h)/2-openvg.VGfloat(imh)/2
			openvg.Img(x, y, img)
			openvg.End()
			time.Sleep(*delay)
		}
		if !*loop {
			break
		}
	}
}