[]uint8和[]byte在Golang切片中的区别是什么?

huangapple go评论101阅读模式
英文:

Difference between []uint8 && []byte (Golang Slices)

问题

我正在运行的一个函数是:image.Decode()

image.Decode函数接受一个io.Reader类型的参数,而io.Reader函数接受一个[]byte类型的参数。

当我传入一个[]uint8类型的参数时,会出现以下错误:

panic: image: unknown format

如何将[]uint8转换为[]byte?

更新

错误发生在星号标记的位置,因为image.Decode无法读取变量xxx。

    package main

    import (
        "github.com/nfnt/resize"
        "image"
        "image/jpeg"
        "fmt"
        "launchpad.net/goamz/aws"
        "launchpad.net/goamz/s3"
        "bytes"
        "encoding/json"
        "io/ioutil"
        "os"
        "reflect"
    )

    type Data struct {
        Key string
    }

    func main() {

      useast := aws.USEast

      connection := s3.New(auth, useast)
      mybucket := connection.Bucket("bucketName")

      image_data, err := mybucket.Get("1637563605030")

      if err != nil {
        panic(err.Error())
      } else {
        fmt.Println("success")
      }

      xxx := []byte(image_data)

      ******* 错误发生在这里 **************

      original_image, _, err := image.Decode(bytes.NewReader(xxx))

      ******* 错误发生在这里结束 **************

      if err != nil {
        fmt.Println("Shit")
        panic(err.Error())
      } else {
        fmt.Println("Another success")
      }

      new_image := resize.Resize(160, 0, original_image, resize.Lanczos3)

      if new_image != nil {
        fmt.Println("YAY")
      }
    }
英文:

One of the functions I am running: image.Decode()

The image.Decode function takes in an io.Reader && and the io.Reader function takes in a []byte.

When I pass in a []uint8, if gives me this error:

panic: image: unknown format

How do I convert the []uint8 to []byte?

UPDATE

The error is happening at the starred area because image.Decode can't read the variable xxx.

    package main

    import (
        "github.com/nfnt/resize"
        "image"
        "image/jpeg"
        "fmt"
        "launchpad.net/goamz/aws"
        "launchpad.net/goamz/s3"
        "bytes"
        "encoding/json"
        "io/ioutil"
        "os"
        "reflect"
    )

    type Data struct {
        Key string
    }

    func main() {

      useast := aws.USEast

      connection := s3.New(auth, useast)
      mybucket := connection.Bucket("bucketName")

      image_data, err := mybucket.Get("1637563605030")

      if err != nil {
        panic(err.Error())
      } else {
        fmt.Println("success")
      }

      xxx := []byte(image_data)

      ******* THIS IS WHERE THE ERROR OCCURS **************

      original_image, _, err := image.Decode(bytes.NewReader(xxx))

      ******* THIS IS WHERE THE ERROR OCCURS END **************

      if err != nil {
        fmt.Println("Shit")
        panic(err.Error())
      } else {
        fmt.Println("Another success")
      }

      new_image := resize.Resize(160, 0, original_image, resize.Lanczos3)

      if new_image != nil {
        fmt.Println("YAY")
      }
    }

答案1

得分: 61

《Go编程语言规范》

数值类型

uint8       所有无符号8位整数的集合(0到255)

byte        uint8的别名

package main

import "fmt"

func ByteSlice(b []byte) []byte { return b }

func main() {
    b := []byte{0, 1}
    u8 := []uint8{2, 3}
    fmt.Printf("%T %T\n", b, u8)
    fmt.Println(ByteSlice(b))
    fmt.Println(ByteSlice(u8))
}

输出:

[]uint8 []uint8
[0 1]
[2 3]

你误诊了你的问题。

英文:

> The Go Programming Language Specification
>
> Numeric types
>
> uint8 the set of all unsigned 8-bit integers (0 to 255)
>
> byte alias for uint8


package main

import "fmt"

func ByteSlice(b []byte) []byte { return b }

func main() {
	b := []byte{0, 1}
	u8 := []uint8{2, 3}
	fmt.Printf("%T %T\n", b, u8)
	fmt.Println(ByteSlice(b))
	fmt.Println(ByteSlice(u8))
}

Output:

[]uint8 []uint8
[0 1]
[2 3]

You have misdiagnosed your problem.

答案2

得分: 7

如其他答案所解释的那样,将[]uint8传递给需要[]byte的情况是没有问题的。如果这是你的问题,你会得到一个编译时错误。但你没有得到编译时错误,而是得到了一个运行时错误,这是由图像库在读取切片中的数据时抛出的panic错误。

实际上,图像库只是部分引起了你的问题。请参考http://golang.org/src/pkg/image/format.go。它返回一个错误消息,因为它无法识别切片中数据的图像格式。你的代码调用了image.Decode(),当image.Decode()返回错误消息时,它会调用panic

英文:

As the other answers have explained, there's no problem passing a []uint8 where a []byte is required. If this was your problem, you'd be getting a compile time error. You aren't. A panic is a runtime error, and it's being thrown by the image library when it reads the data in the slice.

In fact, the image library is only partially your problem. See http://golang.org/src/pkg/image/format.go. It's returning an error message because it doesn't recognize the image format of the data in the slice. Your code, which calls image.Decode() is calling panic when image.Decode() returns the error message.

答案3

得分: -1

如果你有一个变量imageData,类型是[]uint8,你可以传递[]byte(imageData)

参考:http://golang.org/ref/spec#Conversions

英文:

If you have a variable imageData that is []uint8 you may pass []byte(imageData)

See http://golang.org/ref/spec#Conversions

huangapple
  • 本文由 发表于 2014年4月9日 07:52:52
  • 转载请务必保留本文链接:https://go.coder-hub.com/22950392.html
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