Golang如何在不旋转的情况下上传外部图像

Question

I have been working on an image upload functionality for a few weeks and I just about have it done. I am using Golang as a backend language and it's purpose is to upload images sent from IOS devices to amazon s3 . In the process of uploading the image I also resize them and this has caused problems primarily the decode method sometimes rotates images which I do not want

file, handler, err := r.FormFile("file")
        if err != nil {
            fmt.Println("Error Uploading Image")
            return
        }
        defer file.Close()
         // the code below sometimes rotates an image
        img,err := imaging.Decode(file)
        if err != nil {
            print("Imaging Open error")
        }
      new_image := imaging.Resize(img,400,400, imaging.Lanczos)

The library I am using is this one https://github.com/disintegration/imaging which is fantastic and the example they showed was this

src, err := imaging.Open("testdata/lena_512.png")
    if err != nil {
        log.Fatalf("Open failed: %v", err)
    }

    src = imaging.Resize(src, 256, 0, imaging.Lanczos)

That example is fine however my images are not stored locally they are coming from IOS devices is there something that I can do to fix this problem ? Some of my images are being saved like this

Some images are rotated like this and it is the Decode method doing it

I can correct it by rotating the image however some other images that do not get rotated by decode end up being rotated by the Rotate270 method .

img,err := imaging.Decode(file)
        if err != nil {
            print("Imaging Open error")
        }
         // rotate the image
        img = imaging.Rotate270(img)

        new_image := imaging.Resize(img,400,400, imaging.Lanczos)

This is how the image is saved and looks after I rotate it . Is there someway I can upload external images without having to use decode or just fixing the decode issue ? Imaging.Resize first parameter takes in type image.Image and here is my full code

func myImages(w http.ResponseWriter, r *http.Request) {
    r.ParseForm()
    var buff bytes.Buffer
file, handler, err := r.FormFile("file")
        if err != nil {
            fmt.Println("Error Uploading Image")
            return
        }
        defer file.Close()

        img,err := imaging.Decode(file)
        if err != nil {
            print("Imaging Open error")
        }


        new_image := imaging.Resize(img,400,400, imaging.Lanczos)
        var buf bytes.Buffer




        err = imaging.Encode(&buf,new_image, imaging.JPEG)
        if err != nil {
            log.Println(err)
            return
        }
    }

Answer 1

Unfortunately the go stdlib image package does not handle images which are marked as rotated with exif tags (like those here taken on a device upside down). The bug about this is here:

https://github.com/golang/go/issues/4341

You can see an example of handling this in camlistore, but it is quite involved:

https://camlistore.googlesource.com/camlistore/+/master/pkg/images/images.go

First you have to decode exif options (DecodeOpts), then you have to check which orientation it has (out of 8 possible), then rotate as necessary. It's painful and there is no easy solution as yet. You can use this package to read exif data though:

https://github.com/rwcarlsen/goexif