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< ol class = "chapter" > < li class = "chapter-item expanded affix " > < a href = "../index.html" > Go语言圣经< / a > < / li > < li class = "chapter-item expanded affix " > < a href = "../preface.html" > 前言< / a > < / li > < li class = "chapter-item expanded " > < a href = "../ch1/ch1.html" > < strong aria-hidden = "true" > 1.< / strong > 入门< / a > < / li > < li > < ol class = "section" > < li class = "chapter-item expanded " > < a href = "../ch1/ch1-01.html" > < strong aria-hidden = "true" > 1.1.< / strong > Hello, World< / a > < / li > < li class = "chapter-item expanded " > < a href = "../ch1/ch1-02.html" > < strong aria-hidden = "true" > 1.2.< / strong > 命令行参数< / a > < / li > < li class = "chapter-item expanded " > < a href = "../ch1/ch1-03.html" > < strong aria-hidden = "true" > 1.3.< / strong > 查找重复的行< / a > < / li > < li class = "chapter-item expanded " > < a href = "../ch1/ch1-04.html" class = "active" > < strong aria-hidden = "true" > 1.4.< / strong > GIF动画< / a > < / li > < li class = "chapter-item expanded " > < a href = "../ch1/ch1-05.html" > < strong aria-hidden = "true" > 1.5.< / strong > 获取URL< / a > < / li > < li class = "chapter-item expanded " > < a href = "../ch1/ch1-06.html" > < strong aria-hidden = "true" > 1.6.< / strong > 并发获取多个URL< / a > < / li > < li class = "chapter-item expanded " > < a href = "../ch1/ch1-07.html" > < strong aria-hidden = "true" > 1.7.< / strong > Web服务< / a > < / li > < li class = "chapter-item expanded " > < a href = "../ch1/ch1-08.html" > < strong aria-hidden = "true" > 1.8.< / strong > 本章要点< / a > < / li > < / ol > < / li > < li class = "chapter-item expanded " > < a href = "../ch2/ch2.html" > < strong aria-hidden = "true" > 2.< / strong > 程序结构< / a > < / li > < li > < ol class = "section" > < li class = "chapter-item expanded " > < a href = "../ch2/ch2-01.html" > < strong aria-hidden = "true" > 2.1.< / strong > 命名< / a > < / li > < li class = "chapter-item expanded " > < a href = "../ch2/ch2-02.html" > < strong aria-hidden = "true" > 2.2.< / strong > 声明< / a > < / li > < li class = "chapter-item expanded " > < a href = "../ch2/ch2-03.html" > < strong aria-hidden = "true" > 2.3.< / strong > 变量< / a > < / li > < li class = "chapter-item expanded " > < a href = "../ch2/ch2-04.html" > < strong aria-hidden = "true" > 2.4.< / strong > 赋值< / a > < / li > < li class = "chapter-item expanded " > < a href = "../ch2/ch2-05.html" > < strong aria-hidden = "true" > 2.5.< / strong > 类型< / a > < / li > < li class = "chapter-item expanded " > < a href = "../ch2/ch2-06.html" > < strong aria-hidden = "true" > 2.6.< / strong > 包和文件< / a > < / li > < li class = "chapter-item expanded " > < a href = "../ch2/ch2-07.html" > < strong aria-hidden = "true" > 2.7.< / strong > 作用域< / a > < / li > < / ol > < / li > < li class = "chapter-item expanded " > < a href = "../ch3/ch3.html" > < strong aria-hidden = "true" > 3.< / strong > 基础数据类型< / a > < / li > < li > < ol class = "section" > < li class = "chapter-item expanded " > < a href = "../ch3/ch3-01.html" > < strong aria-hidden = "true" > 3.1.< / strong > 整型< / a > < / li > < li class = "chapter-item expanded " > < a href = "../ch3/ch3-02.html" > < strong aria-hidden = "true" > 3.2.< / strong > 浮点数< / a > < / li > < li class = "chapter-item expanded " > < a href = "../ch3/ch3-03.html" > < strong aria-hidden = "true" > 3.3.< / strong > 复数< / a > < / li > < li class = "chapter-item expanded " > < a href = "../ch3/ch3-04.html" > < strong aria-hidden = "true" > 3.4.< / strong > 布尔型< / a > < / li > < li class = "chapter-item expanded " > < a href = "../ch3/ch3-05.html" > < strong aria-hidden = "true" > 3.5.< / strong > 字符串< / a > < / li > < li class = "chapter-item expanded " > < a href = "../ch3/ch3-06.html" > < strong aria-hidden = "true" > 3.6.< / strong > 常量< / a > < / li > < / ol > < / li > < li class = "chapter-item expanded " > < a href = "../ch4/ch4.html" > < strong aria-hidden = "true" > 4.< / strong > 复合数据类型< / a > < / li > < li > < ol class = "section" > < li class = "chapter-item expanded " > < a href = "../ch4/ch4-01.html" > < strong aria-hidden = "true" > 4.1.< / strong > 数组< / a > < / li > < li class = "chapter-item expanded " > < a href = "../ch4/ch4-02.html" > < strong aria-hidden = "true" > 4.2.< / strong > Slice< / a > < / li > < li class = "chapter-item expanded " > < a href = "../ch4/ch4-03.html" > < strong aria-hidden = "true" > 4.3.< / strong > Map< / a > < / li > < li class = "chapter-item expanded " > < a href = "../ch4/ch4-04.html" > < strong aria-hidden = "true" > 4.4.< / strong > 结构体< / a > < / li > < li class = "chapter-item expanded " > < a href = "../ch4/ch4-05.html" > < strong aria-hidden = "true" > 4.5.< / strong > JSON< / a > < / li > < li class = "chapter-item expanded " > < a href = "../ch4/ch4-06.html" > < s
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2022-08-24 10:48:15 +00:00
< li > < em > KusonStack一站式可编程配置技术栈(Go): < a href = "https://github.com/KusionStack/kusion" > https://github.com/KusionStack/kusion< / a > < / em > < / li >
< li > < em > KCL 配置编程语言(Rust): < a href = "https://github.com/KusionStack/KCLVM" > https://github.com/KusionStack/KCLVM< / a > < / em > < / li >
< li > < em > 凹语言™: < a href = "https://github.com/wa-lang/wa" > https://github.com/wa-lang/wa< / a > < / em > < / li >
2022-08-04 06:59:33 +00:00
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< hr >
< h2 id = "14-gif动画" > < a class = "header" href = "#14-gif动画" > 1.4. GIF动画< / a > < / h2 >
< p > 下面的程序会演示Go语言标准库里的image这个package的用法， ， （ ） ， ， < / p >
< p > < img src = "../images/ch1-01.png" alt = "" / > < / p >
< p > 译注： ， （ < code > ./lissajous > output.gif< / code > 命令） ： < / p >
< p > < img src = "../images/ch1-01.gif" alt = "" / > < / p >
< p > 这段代码里我们用了一些新的结构， ， ， ， ， < / p >
< p > < u > < i > gopl.io/ch1/lissajous< / i > < / u > < / p >
< pre > < code class = "language-go" > // Lissajous generates GIF animations of random Lissajous figures.
package main
import (
" image"
" image/color"
" image/gif"
" io"
" math"
" math/rand"
" os"
" time"
)
var palette = []color.Color{color.White, color.Black}
const (
whiteIndex = 0 // first color in palette
blackIndex = 1 // next color in palette
)
func main() {
// The sequence of images is deterministic unless we seed
// the pseudo-random number generator using the current time.
// Thanks to Randall McPherson for pointing out the omission.
rand.Seed(time.Now().UTC().UnixNano())
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 = 64 // 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 := 0; 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),
blackIndex)
}
phase += 0.1
anim.Delay = append(anim.Delay, delay)
anim.Image = append(anim.Image, img)
}
gif.EncodeAll(out, & anim) // NOTE: ignoring encoding errors
}
< / code > < / pre >
< p > 当我们import了一个包路径包含有多个单词的package时， （ ） ， ， ， < / p >
< p > 这个程序里的常量声明给出了一系列的常量值， ， ， ， ， < / p >
< p > []color.Color{...}和gif.GIF{...}这两个表达式就是我们说的复合声明（ ） ， < / p >
< p > gif.GIF是一个struct类型（ ） ， ， ； （ ） ， < / p >
< p > lissajous函数内部有两层嵌套的for循环。外层循环会循环64次， ， （ ） ， ， ， ， ， ， ， < / p >
< p > 内层循环设置两个偏振值。x轴偏振使用sin函数。y轴偏振也是正弦波， ， ， < / p >
< p > main函数调用lissajous函数， ， < / p >
< pre > < code > $ go build gopl.io/ch1/lissajous
$ ./lissajous > out.gif
< / code > < / pre >
< p > < strong > 练习 1.5： < / strong > 修改前面的Lissajous程序里的调色板， < code > color.RGBA{0xRR, 0xGG, 0xBB, 0xff}< / code > 来得到< code > #RRGGBB< / code > 这个色值，三个十六进制的字符串分别代表红、绿、蓝像素。< / p >
< p > < strong > 练习 1.6： < / strong > 修改Lissajous程序， ， ， < / p >
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