Golang从URL读取变量

描述

修改 Lissajour 服务，从 URL 读取 变量（Go 语言圣经书后习题 1.12）

题目

修改 Lissajour 服务，从 URL 读取变量，比如你可以访问 http://localhost:8000/?cycles=20 这个URL，这样访问可以将程序里的 cycles 默认的 5 修改为 20。字符串 转换为 数字 可以调用 strconv.Atoi 函数。你可以在 godoc 里查看 strconv.Atoi 的详细说明。

题目解决思路

解析 URL 即可。

代码具体实现

package main
import (
	"fmt"
	"image"
	"image/color"
	"image/gif"
	"io"
	"math"
	"math/rand"
	"strconv"
)
import (
	"log"
	"net/http"
	"time"
)
var palette = []color.Color{color.White, color.Black}
const (
	whiteIndex = 0
	blackIndex = 1
)
type lconfig struct {
	cycles float64
	res    float64
	freq   float64
	size   int
	frames int
	delay  int
}
func main() {
	fmt.Println("嗨客网(www.haicoder.net)")
	rand.Seed(time.Now().UnixNano())
	lconf := lconfig {
		cycles  : 5,
		res     : 0.001,
		freq    : rand.Float64() * 3.0,
		size    : 100,
		frames  : 64,
		delay   : 8,
	}
	http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
		confs := r.URL.Query()
		for i, c := range confs {
			switch i {
			case "cycles" : lconf.cycles, _ = strconv.ParseFloat( c[0], 64 )
			case "freq"   : lconf.freq  , _ = strconv.ParseFloat( c[0], 64 )
			case "res"    : lconf.res   , _ = strconv.ParseFloat( c[0], 64 )
			case "size"   : lconf.size  , _ = strconv.Atoi( c[0] )
			case "frames" : lconf.frames, _ = strconv.Atoi( c[0] )
			case "delay"  : lconf.delay , _ = strconv.Atoi( c[0] )
			}
		}
		lissajous(w, lconf)
	})
	log.Fatal(http.ListenAndServe("localhost:8000", nil))
	return
}
func lissajous(out io.Writer, set lconfig) {
	anim := gif.GIF{LoopCount: set.frames}
	phase := 0.0 // phase difference
	for i := 0; i < set.frames; i++ {
		rect := image.Rect(0, 0, 2*set.size+1, 2*set.size+1)
		img := image.NewPaletted(rect, palette)
		for t := 0.0; t < set.cycles*2*math.Pi; t += set.res {
			x := math.Sin(t)
			y := math.Sin(t*set.freq + phase)
			img.SetColorIndex(set.size+int(x*float64(set.size)+0.5), set.size+int(y*float64(set.size)+0.5), blackIndex)
		}
		phase += 0.1
		anim.Delay = append(anim.Delay, set.delay)
		anim.Image = append(anim.Image, img)
	}
	gif.EncodeAll(out, &anim)
}

我们直接运行如上程序即可。