image/png: invalid format: not a PNG file

[trankten]

What version of Go are you using (go version)?

1.17.6

Does this issue reproduce with the latest release?

Yes

What operating system and processor architecture are you using (go env)?

go env Output

set GO111MODULE=
set GOARCH=amd64
set GOBIN=L:\Go\apps
set GOCACHE=C:\Users\Trankten\AppData\Local\go-build
set GOENV=C:\Users\Trankten\AppData\Roaming\go\env
set GOEXE=.exe
set GOEXPERIMENT=
set GOFLAGS=
set GOHOSTARCH=amd64
set GOHOSTOS=windows
set GOINSECURE=
set GOMODCACHE=C:\Users\Trankten\go\pkg\mod
set GONOPROXY=
set GONOSUMDB=
set GOOS=windows
set GOPATH=C:\Users\Trankten\go
set GOPRIVATE=
set GOPROXY=https://proxy.golang.org,direct
set GOROOT=L:\Go
set GOSUMDB=sum.golang.org
set GOTMPDIR=
set GOTOOLDIR=L:\Go\pkg\tool\windows_amd64
set GOVCS=
set GOVERSION=go1.17.6
set GCCGO=gccgo
set AR=ar
set CC=gcc
set CXX=g++
set CGO_ENABLED=1
set GOMOD=L:\Go\APP\color\go.mod
set CGO_CFLAGS=-g -O2
set CGO_CPPFLAGS=
set CGO_CXXFLAGS=-g -O2
set CGO_FFLAGS=-g -O2
set CGO_LDFLAGS=-g -O2
set PKG_CONFIG=pkg-config
set GOGCCFLAGS=-m64 -mthreads -fmessage-length=0 -fdebug-prefix-map=C:\TMP\go-build1644488097=/tmp/go-build -gno-record-gcc-switches

What did you do?

package main

import (
	"fmt"
	"image"
	"image/gif"
	"image/jpeg"
	"image/png"
	"os"
)

func main() {
	fh, err := os.Open("file.png")

	if err != nil {
		fmt.Println("ERR 1: " + err.Error())
		os.Exit(1)
	}
	_, format, err := image.DecodeConfig(fh)
	if (format != "jpeg" && format != "gif" && format != "png") || err != nil {
		fmt.Println("ERR 2: " + err.Error())
		os.Exit(1)
	}

	if format == "png" {
		_, err = png.Decode(fh)
	} else if format == "jpg" {
		_, err = jpeg.Decode(fh)
	} else if format == "gif" {
		_, err = gif.Decode(fh)
	} else {
		fmt.Println("ERR 3: " + err.Error())
		os.Exit(1)
	}
	if err != nil {
		fmt.Println("ERR 4: " + err.Error())
		os.Exit(1)
	}

	fmt.Println("Read OK.")

	os.Exit(1)
}

What did you expect to see?

"Read OK"

What did you see instead?

ERR 4: png: invalid format: not a PNG file

[trankten]

Fixed. Forgot to Seek back to 0,0

fh.Seek(0, 0)

[nidhi-canopas]

@trankten i'm facing the similar problem. I had tried the solution given by you, but unfortunately fix hadn't worked for me.
The only difference in my case is i'm taking file from request and not opening from os.
Here's the code

file, err := header.Open() /* get file from header */
	if err != nil {
		panic("error from opening the file : ", err)
	}
	
	file.Seek(0, 0)
	
	config, format, err := image.DecodeConfig(file) /* decode image config */

	if err != nil {
		panic("error in getting config : ", err)
	}
	
	var imageDecoded image.Image
	if format == "png" {
		imageDecoded, err = png.Decode(file) /* decode png image */
	} else {
		imageDecoded, err = jpeg.Decode(file) /* decode jpg/jpeg image */
	}

	if err != nil {
		panic("error in decoding the image : ", err)
	}

Can you please help to guide me what i'm doing wrong?