index error in ocontour

[ma-ho]

Hi,

apparently, ocontour returns 0-based index matrices
while R requires 1-based indices.

As an example, consider the mask image:

msk = as.Image(matrix(0,nrow=5,ncol=5))
msk[,3] = msk[3,] = msk[2,2] = msk[2,4] = msk[4,2] = msk[4,4] = 1
msk

Image
colorMode : Grayscale
storage.mode : double
dim : 5 5
frames.total : 1
frames.render: 1

imageData(object)[1:5,1:5]
[,1] [,2] [,3] [,4] [,5]
[1,] 0 0 1 0 0
[2,] 0 1 1 1 0
[3,] 1 1 1 1 1
[4,] 0 1 1 1 0
[5,] 0 0 1 0 0

Then ocontour of msk outputs:

con = ocontour(msk)[[1]]
con

[,1] [,2]

[1,] 2 0
[2,] 1 1
[3,] 0 2
[4,] 1 3
[5,] 2 4
[6,] 3 3
[7,] 4 2
[8,] 3 1

while the 1-based output would be
con+1

 [,1] [,2]

[1,] 3 1
[2,] 2 2
[3,] 1 3
[4,] 2 4
[5,] 3 5
[6,] 4 4
[7,] 5 3
[8,] 4 2

I am running R version 4.2.3 (2023-03-15) with EBImage_4.38.0 attached.

[aoles]

Thanks for reporting this! Indeed, looks like a bug to me. In case you have started looking into a fix, please feel free to submit a PR. Cheers!