image/draw: subimage rectangle's MIN point is not start (0,0)

[leexingliang]

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

go version go1.12.1 linux/amd64

Does this issue reproduce with the latest release?

Not

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

GOARCH="amd64"
GOBIN=""
GOCACHE="/home/work/.cache/go-build"
GOEXE=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOOS="linux"
GOPATH="/home/work/go"
GOPROXY=""
GORACE=""
GOROOT="/usr/local/go"
GOTMPDIR=""
GOTOOLDIR="/usr/local/go/pkg/tool/linux_amd64"
GCCGO="gccgo"
CC="gcc"
CXX="g++"
CGO_ENABLED="1"
GOMOD="/home/work/fencoder/huifang-fencoder/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-build595600236=/tmp/go-build -gno-record-gcc-switches"

What did you do?

I want to capture part of the RGBA image with rectangle by using image.RGBA.SubImage funcation.

func subimage(src *image.RGBA, rect image.Rectangle) *image.RGBA {
	// src.Rect = image.Rectangle{
	// 	Min: image.Point{0, 0},
	// 	Max: image.Point{1000, 1000},
	// }

	dstrect := image.Rect(100, 100, 200, 200)
	dstimage := src.SubImage(dstrect)

        fmt.Println("dstimage rectangle: ", dstimage.Bounds())
        return dstimage.(*image.RGBA)
}

What did you expect to see?

dstimage rectangle: (0,0)-(100,100)

that equal image.Rect(0, 0, rect.Dx(), rect.Dy())

What did you see instead?

for above code

dstimage rectangle: (100,100)-(200,200)

[nigeltao]

This is intentional. See https://blog.golang.org/go-image-package, which says that "A common mistake is assuming that an Image's bounds start at (0, 0)".

[nigeltao]

Judging from the issue title, "subimage rectangle's MIN point is not (0,0)", I assume that you are expecting that dstimage's rectangle starts at (0, 0).

In other words, the "What did you expect to see?" and "What did you see instead?" sections' contents should be swapped around.

[leexingliang]

Judging from the issue title, "subimage rectangle's MIN point is not (0,0)", I assume that you are expecting that dstimage's rectangle starts at (0, 0).

In other words, the "What did you expect to see?" and "What did you see instead?" sections' contents should be swapped around.

yeah, i will mod it