image/png: invalid format: chunk out of order

[kmicki]

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

$ go version
go version go1.17.6 linux/amd64

Does this issue reproduce with the latest release?

yes

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

go env Output

$ go env
GO111MODULE="off"
GOARCH="amd64"
GOBIN=""
GOCACHE="/home/deck/.cache/go-build"
GOENV="/home/deck/.config/go/env"
GOEXE=""
GOEXPERIMENT=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOINSECURE=""
GOMODCACHE="/home/deck/go/pkg/mod"
GONOPROXY=""
GONOSUMDB=""
GOOS="linux"
GOPATH="/home/deck/go"
GOPRIVATE=""
GOPROXY="https://proxy.golang.org,direct"
GOROOT="/usr/lib/go"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/usr/lib/go/pkg/tool/linux_amd64"
GOVCS=""
GOVERSION="go1.17.6"
GCCGO="gccgo"
AR="ar"
CC="gcc"
CXX="g++"
CGO_ENABLED="1"
GOMOD=""
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
PKG_CONFIG="pkg-config"
GOGCCFLAGS="-fPIC -m64 -pthread -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build3730379239=/tmp/go-build -gno-record-gcc-switches"

What did you do?

Try to decode e.g. this file with png.Decode().

What did you expect to see?

No error and decoded image.

What did you see instead?

invalid format: chunk out of order

What I think is the cause

It looks like the problem is here.

This code expects that PLTE chunk is present only for Color type = 3 (Paletted). If it is present for other types, the mentioned error is thrown.

According to PNG specification, PLTE chunk may appear also for types 2 or 6. The PNG file linked above is type 2 and contains PLTE chunk, so it is compliant with PNG specs.

[seankhliao]

cc @nigeltao