func light(x, y, r openvg.VGfloat, c openvg.RGB) {
stops := []openvg.Offcolor{
{0.0, c, 1},
{0.50, openvg.RGB{c.Red / 2, c.Green / 2, c.Blue / 2}, 1},
}
openvg.FillRadialGradient(x, y, (x+r)*.90, y, r, stops)
}
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() {
width, height := openvg.Init() // OpenGL, etc initialization
w2 := openvg.VGfloat(width / 2)
h2 := openvg.VGfloat(height / 2)
w := openvg.VGfloat(width)
stops := []openvg.Offcolor{
{0.0, openvg.RGB{44, 100, 232}, 1.0}, // blue-ish
{0.5, openvg.RGB{22, 50, 151}, 1.0}, // darker blue
{1.0, openvg.RGB{88, 200, 255}, 1.0}, // lighter blue
}
openvg.Start(width, height) // Start the picture
openvg.BackgroundColor("black") // Black background
openvg.FillRadialGradient(w2, 0, w2, w2, w*.5, stops) // 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.SaveEnd("hvg.raw") // End the picture
openvg.End()
bufio.NewReader(os.Stdin).ReadBytes('\n') // Pause until [RETURN]
openvg.Finish() // Graphics cleanup
}