练习 1.5： 修改前面的Lissajous程序里的调色板，由黑色改为绿色。我们可以用color.RGBA{0xRR, 0xGG, 0xBB, 0xff}来得到#RRGGBB这个色值，三个十六进制的字符串分别代表红、绿、蓝像素。

练习 1.6： 修改Lissajous程序，修改其调色板来生成更丰富的颜色，然后修改SetColorIndex的第三个参数，看看显示结果吧。

 

package mainimport (        "image"        "image/color"        "image/gif"        "io"        "math"        "math/rand"        "os") //定义调色板var palette = []color.Color{ color.RGBA{255,255,255,math.MaxUint8}, color.Black, color.RGBA{0,0,128,math.MaxUint8},color.RGBA{30,144,255,math.MaxUint8},color.RGBA{72,61,139,math.MaxUint8},color.RGBA{255,0,255,math.MaxUint8},color.RGBA{124,252,0,math.MaxUint8}}const (        whiteIndex = 0 // first color in palette        blackIndex = 1 // next color in palette        greenIndex = 2 // next color in palette 定义新的颜色)func main() {        lissajous(os.Stdout)}func lissajous(out io.Writer) {        const (                cycles  = 5     // number of complete x oscillator revolutions                res     = 0.001 // angular resolution                size    = 100   // image canvas covers [-size..+size]                nframes = 128    // number of animation frames                delay   = 8     // delay between frames in 10ms units        )        freq := rand.Float64() * 3.0 // relative frequency of y oscillator        anim := gif.GIF{LoopCount: nframes}        phase := 0.0 // phase difference        for i,c := 0,1; i < nframes; i++ {                rect := image.Rect(0, 0, 2*size+1, 2*size+1)                img := image.NewPaletted(rect, palette)                for t := 0.0; t < cycles*2*math.Pi; t += res {                        x := math.Sin(t)                        y := math.Sin(t*freq + phase)                        img.SetColorIndex(size+int(x*size+0.5), size+int(y*size+0.5),uint8(c)) //使用新的颜色                }                c ++ //修改颜色选择                if c >= len(palette) {    　　　　　　　　　　  c = 1                }                phase += 0.1                anim.Delay = append(anim.Delay, delay)                anim.Image = append(anim.Image, img)        }        gif.EncodeAll(out, &anim) // NOTE: ignoring encoding errors}