ch1/ch1-04

[giscus[bot]]

ch1/ch1-04

中文版

https://gopl-zh.github.io/ch1/ch1-04.html

[stpJing]

这里直接复制代码输出

$ go build gopl.io/ch1/lissajous
$ ./lissajous >out.gif

生成的gif是无法打开的
但是如果这样调用是可以的

	create, _ := os.Create("out.gif")
	lissajous(create)

64位win10，go1.19rc2亲测，为什么会这样?

[chai2010]

diff看看，应该是windows搞的鬼，把stdout特化了

[stpJing]

不能说很像，只能说完全不一样了
正常输出文件头部是GIF89a
stdout搞出来的是G I F 8 9 A，每一个都多了一个00，后面更是插入了无数个空格，最后正常生成的gif只有213kB，stdout生成的是314kB

[stpJing]

我之前是用的IDEA的命令行有这个问题，现在用CMD没有这个问题了，但是CMD出来的只有76kB，然后出来的图像是竖着的-。-

[Steve-Lee-CST]

Windows下powershell的问题
关于这个情况，比较明确的解释：
https://stackoverflow.com/questions/56323293/go-generated-animated-gifs-didnt-work-in-windows
golang/go#13746

reference:
golang/go#42337
https://www.cnblogs.com/linxiaoxu/p/16187331.html

[fool-yf]

mac m3 pro 也必须在build之后，运行./lissajous >out.gif命令才能正常展示

[Zengyinjun]

package main

import (
	"image"
	"image/color"
	"image/gif"
	"io"
	"math"
	"math/rand"
	"os"
	"time"
)

var palette = []color.Color{color.White, color.RGBA{0, 0xff, 0, 0xff},
	color.RGBA{0, 0, 0xff, 0xff}, color.RGBA{0xff, 0, 0, 0xff},
	color.RGBA{0x22, 0x22, 0x22, 0xff}, color.RGBA{0xff, 0x44, 0x15, 0xff},
	color.RGBA{0x44, 0x62, 0x12, 0xff}, color.RGBA{0xff, 0xff, 0x15, 0xff}}

const (
	whiteIndex = 0 // first color in palette
	greenIndex = 1 // next color in palette
	blueIndex  = 2
	redIndex   = 3
)

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
	colorIndex := 1
	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),
				uint8(colorIndex))
		}
		colorIndex = (colorIndex % 7) + 1
		phase += 0.1
		anim.Delay = append(anim.Delay, delay)
		anim.Image = append(anim.Image, img)
	}
	gif.EncodeAll(out, &anim) // NOTE: ignoring encoding errors
}

[ToviHe]

// Lissajous generates GIF animations of random Lissajous figures.
package main

import (
	"image"
	"image/color"
	"image/gif"
	"io"
	"math"
	"math/rand"
	"os"
	"time"
)

// 练习1.5 调色板由黑色变成绿色
var palette = []color.Color{color.White, color.Black, color.RGBA{0xff, 0x00, 0x00, 0xff}, color.RGBA{0x00, 0xff, 0x00, 0xff}, color.RGBA{0x00, 0x00, 0xff, 0xff}}

// 练习1.6 调色板颜色增多
const (
	whiteIndex = 0 // first color in palette
	blackIndex = 1 // next color in palette
	redIndex   = 2
	greenIndex = 3
	blueIndex  = 4
)

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
	)
	colorIndex := uint8(0)
	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),
				colorIndex)
		}
		colorIndex = (colorIndex + 1) % uint8(len(palette))
		phase += 0.1
		anim.Delay = append(anim.Delay, delay)
		anim.Image = append(anim.Image, img)
	}
	gif.EncodeAll(out, &anim) // NOTE: ignoring encoding errors
}

[xm-xw]

直接down下来的代码在win环境，是有问题的，需要修改后使用。
可以在main函数中直接输出文件名
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())
create, _ := os.Create("out.gif")
lissajous(create)
}

[GaytHub]

打卡，ps：这章好多没看懂

[Apahno]

AI时代打卡，复制粘贴了代码下来，哪里不懂搜哪里，练习答案都是看评论的我深深自责