Following readme decode example gives errors in imageToRGBA

[scottleedavis]

From this file (near copied from readme) https://github.com/scottleedavis/mattermost-plugin-watermark/blob/master/decode.go

func main() {
	inFile, _ := os.Open("./assets/test.jpg") // opening file
	inFile.Close()

	reader := bufio.NewReader(inFile) // buffer reader
	img, _, _ := image.Decode(reader) // decoding to golang's image.Image

	sizeOfMessage := steganography.GetMessageSizeFromImage(img) // retrieving message size to decode in the next line

	msg := steganography.Decode(sizeOfMessage, img) // decoding the message from the file
	fmt.Println(string(msg))
}

gives the following error when run

$ go run decode.go 
panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x20 pc=0x10b01e7]

goroutine 1 [running]:
gopkg.in/auyer/steganography%2ev2.imageToRGBA(0x0, 0x0, 0x0)
        /Users/scottd/go/pkg/mod/gopkg.in/auyer/[email protected]/steganography.go:339 +0x37
gopkg.in/auyer/steganography%2ev2.decode(0x400000000, 0x0, 0x0, 0x10c3080, 0x1, 0xc0000a8000)
        /Users/scottd/go/pkg/mod/gopkg.in/auyer/[email protected]/steganography.go:202 +0x35
gopkg.in/auyer/steganography%2ev2.GetMessageSizeFromImage(0x0, 0x0, 0x0)
        /Users/scottd/go/pkg/mod/gopkg.in/auyer/[email protected]/steganography.go:237 +0x48
main.main()
        /Users/scottd/workspace/mattermost-plugin-watermark/decode.go:20 +0x195
exit status 2

[auyer]

Hi, thanks for looking into this.
There are a few thing to point out:

1. inFile.Close() cant happen before reader := bufio.NewReader(inFile). I'm updating the readme with a defer in this call.
2. You should check for errors when running the code for real. This is omitted for brevity in the readme, but maybe I should re-introduce it. This would have caught what I pointed at in 1
3. I will investigate compatibility issues with jpeg images. For now, try using PNGs when possible.

[scottleedavis]

1 & 2 : Done. thank you
3: Excellent! I would really appreciate jpg support as well. I'd be happy to contribute to that as well.

I confirm with the above 1 & 2 changes, png works as intended.

[scottleedavis]

In regards to jpg support, reposting a conversation from https://gist.github.com/scottleedavis/25f5e7d1b97dcb8964b74712cfbc6a29 for visibility here.

jpg test with decode.go, with above approach has this output currently.

$ go run decode.go ./assets/test.jpg 
panic: runtime error: slice bounds out of range

goroutine 1 [running]:
gopkg.in/auyer/steganography%2ev2.decodeRGBA(0xffffffff00000004, 0xc0000b6080, 0xc0000b6080, 0x4, 0x8)
        /Users/scottd/go/pkg/mod/gopkg.in/auyer/[email protected]/steganography.go:180 +0x5a8
gopkg.in/auyer/steganography%2ev2.decode(0xffffffff00000004, 0x1113040, 0xc00014e080, 0xc0000aa000, 0x1113040, 0xc00014e080)
        /Users/scottd/go/pkg/mod/gopkg.in/auyer/[email protected]/steganography.go:203 +0x53
gopkg.in/auyer/steganography%2ev2.Decode(...)
        /Users/scottd/go/pkg/mod/gopkg.in/auyer/[email protected]/steganography.go:217
main.main()
        /Users/scottd/workspace/mattermost-plugin-watermark/decode.go:44 +0x296
exit status 2

[scottleedavis]

I believe this is something on my side as I just added jpg unit tests in PR #6

Apologies on the noise, thank you for your help