x/image/tiff: grayscale tiled images are not decoded correctly

[zerkms]

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

$ go version
go version go1.13.4 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=""
GOARCH="amd64"
GOBIN=""
GOCACHE="/home/ivan/.cache/go-build"
GOENV="/home/ivan/.config/go/env"
GOEXE=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GONOPROXY=""
GONOSUMDB=""
GOOS="linux"
GOPATH="/srv/work/go"
GOPRIVATE=""
GOPROXY="https://proxy.golang.org,direct"
GOROOT="/home/ivan/.local/share/umake/go/go-lang"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/home/ivan/.local/share/umake/go/go-lang/pkg/tool/linux_amd64"
GCCGO="gccgo"
AR="ar"
CC="gcc"
CXX="g++"
CGO_ENABLED="1"
GOMOD="/srv/work/go/src/go.googlesource.com/image/go.mod"
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-build974283161=/tmp/go-build -gno-record-gcc-switches"

What did you do?

When you decode tiled tiff grayscale image you may find that tiles placed on the image boundary (right) are decoded incorrectly.

It happens because the tiff file contains the complete tile compressed, while the loop iterates only over the part of it that fits the image boundary:

			for y := ymin; y < rMaxY; y++ {
				for x := xmin; x < rMaxX; x++ {

So if you read pixels from the non-complete tiles (from the right edge) all lines but the first one would contain real data mixed with garbage (bits from outside the image boundary).

What did you expect to see?

What did you see instead?

[gopherbot]

Change https://golang.org/cl/211237 mentions this issue: go.image/tiff: fix for decoding grayscale tiled images

[toothrot]

/cc @nigeltao

[nigeltao]

/cc @bsiegert

[zerkms]

Hey team, any chance this to be dragged forward any time soon? It's a pretty significant bug, yet with a simple fix.

[nigeltao]

I dropped some review comments on https://go-review.googlesource.com/c/image/+/211237

Sorry for the late reply.