Here is the full (trimmed) working program:
// Exif project Exif.go
package main
import (
//"bytes"
"encoding/binary"
"fmt"
"os"
)
const JPEGSOIMarker = 0xffd8
const APPMarkerBegin = 0xffe1
const APPMarkerEnd = 0xffef
const ExifEncoding = "II"
type Header struct {
Exif_SOI uint16
APPMarkerTag uint16
MarkerSize uint16
ExifTxt [6]byte
ExifEncoding [2]byte
TagMark uint16
OffsetIDF [4]byte
}
func isJpgImage(header Header) bool {
return header.Exif_SOI == JPEGSOIMarker
}
func isAPPn(header Header) bool {
return header.APPMarkerTag == APPMarkerBegin
}
func readFile(filename string) error {
header := Header{}
in, err := os.Open(filename)
defer func() { in.Close() }()
if err != nil {
return err
}
binary.Read(in, binary.BigEndian, &header)
fmt.Printf("is valid Jpg format: %t\n", isJpgImage(header))
if isJpgImage(header) {
fmt.Printf("%X\n", header.Exif_SOI)
if isAPPn(header) {
fmt.Printf("%X\n", header.APPMarkerTag)
fmt.Printf("Exif %s\n", string(header.ExifTxt[:4]))
fmt.Printf("Intel Encoding %t\n", string(header.ExifEncoding[:2])
== ExifEncoding)
}
}
return nil
}
func main() {
readFile("image.JPG")
}
On Thursday, October 5, 2017 at 8:11:25 PM UTC+2, Ian Davis wrote:
>
>
> On Thu, 5 Oct 2017, at 08:58 AM, Johan terryn wrote:
>
> In following code:
>
>
> type JPGFile struct {
>
> Exif_SOI [2]byte
>
> Exif
>
> }
> type Exif struct { APP1Marker [2]byte APP1DataSize uint16
> ExifHeader [6]byte TIFFHeader[6]byte}
>
> func ReadFile(filename string) (JPGFile, error) {
>
> jpgFile := JPGFile{}
>
> in, err := os.Open(filename)
>
> defer in.Close()
>
> if err != nil {
>
> return jpgFile, err
>
> }
>
> binary.Read(in, binary.LittleEndian, &jpgFile)
>
> return jpgFile, nil
>
> }
>
>
>
>
> *binary.Read* accepts "in" (os.File) as a reader, but if I pass the file
> as a parameter to the function I get the (correct ) error message that "in"
> is not a reader, as defined in the documentation: func Read(r *io.Reader*,
> order ByteOrder, data interface{}) error
>
>
> Or is this working as intended?
>
>
> Can you provide a fuller example showing imports? Your code looks correct
> and "in" is an io.Reader so it's surprising that you are getting that
> message. This non-runnable version of your code compiles fine:
> https://play.golang.org/p/aruCeIHFEZ
>
>
> Ian
>
>
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