将 multipart.File 作为参数放入 image.Decode

Question

multipart.File内容如下："data:image/jpeg;base64,/9j/4AAQSkZJRgABAQAAAQABAAD..."

我正在尝试将其放入 Image.DecodeConfig() 方法中，如下所示：

import (
    "image"
    "image/jpeg"
    "io"
)

func ImgCheckSize(file io.Reader) (io.Reader, error) {
    config, format, err := image.DecodeConfig(file)
...

错误打印："image: unknown format"

我还打印了 multipart.FileHeader.Header，上面写着：

map[Content-Disposition:[form-data; name="img1"; filename="img1"] Content-Type:[application/octet-stream]]

有人遇到过这个吗？任何有用的建议都会有所帮助！非常感谢

Answer 1

正如图像包的文档中所述 (https://golang.org/pkg/image/ 92)，您必须首先注册要使用的格式：

Decoding any particular image format requires the prior registration of a decoder function. Registration is typically automatic as a side effect of initializing that format’s package so that, to decode a PNG image, it suffices to have
import _ “image/png”
in a program’s main package. The _ means to import a package purely for its initialization side effects.

实现示例：https://play.golang.org/p/7d1gS7_tdc0

import (
    "image"
    // Package image/jpeg is not used explicitly in the code below,
    // but is imported for its initialization side-effect, which allows
    // image.Decode to understand JPEG formatted images. 
    _ "image/jpeg"
    "io"
)

func ImgCheckSize(file io.Reader) (io.Reader, error) {
    config, format, err := image.DecodeConfig(file)
...

Answer 2

使用以下包解决："github.com/vincent-petithory/dataurl"

例如：

img解码，_ := dataurl.Decode(imgupload)

将 multipart.File 作为参数放入 image.Decode

Getting a multipart.File into image.Decode as argument

image

multipart

go