3 Channel 2D Images Fail

[muschellij2]

Image from https://radiopaedia.org/cases/hand-arthropathies-distribution-diagram-1

Describe the bug
When you read in a 2D image with multiple channels, normal masking seems to be broken (and likely other operations).

To Reproduce

library(ANTsRCore)
#> 
#> Attaching package: 'ANTsRCore'
#> The following objects are masked from 'package:stats':
#> 
#>     sd, var
#> The following objects are masked from 'package:base':
#> 
#>     all, any, apply, max, min, prod, range, sum
url = "https://user-images.githubusercontent.com/1075118/69453677-66a77d80-0d32-11ea-80ba-c6d5bfeaae53.jpeg"
destfile = tempfile(fileext = ".jpg")
download.file(url, destfile)
img = antsImageRead(destfile)
img > 0
#> antsImage
#>   Pixel Type          : float 
#>   Components Per Pixel: 3 
#>   Dimensions          : 1024x1024 
#>   Voxel Spacing       : 1xNA 
#>   Origin              : 0 NA 
#>   Direction           : 1 0 0 1
dim(img > 0)
#> [1] 1024 1024
img[img > 0]
#> Error in img[img > 0]: Length of mask vector does not match image-region dimensions

split_img = splitChannels(img)
split_img = lapply(split_img, function(x) {
  x / 255
})
gray_img = Reduce(f = "+", split_img)
gray_img > 0
#> antsImage
#>   Pixel Type          : unsigned char 
#>   Components Per Pixel: 1 
#>   Dimensions          : 1024x1024 
#>   Voxel Spacing       : 1x1 
#>   Origin              : 0 0 
#>   Direction           : 1 0 0 1
dim(gray_img > 0)
#> [1] 1024 1024
gray_img[gray_img > 0]
#>     [1] 0.27058825 0.36470589 0.36470589 0.35294119 0.35294119 0.34117648
#>  [ reached getOption("max.print") -- omitted 594406 entries ]

^{Created on 2019-11-22 by the reprex package (v0.3.0.9000)}

Session info

sessioninfo::session_info()
#> ─ Session info ──────────────────────────────────────────────────────────
#>  setting  value                       
#>  version  R version 3.6.0 (2019-04-26)
#>  os       macOS Mojave 10.14.6        
#>  system   x86_64, darwin15.6.0        
#>  ui       X11                         
#>  language (EN)                        
#>  collate  en_US.UTF-8                 
#>  ctype    en_US.UTF-8                 
#>  tz       America/New_York            
#>  date     2019-11-22                  
#> 
#> ─ Packages ──────────────────────────────────────────────────────────────
#>  package     * version   date       lib source                            
#>  ANTsRCore   * 0.7.3     2019-11-05 [1] Github (ANTsX/ANTsRCore@f564041)  
#>  assertthat    0.2.1     2019-03-21 [1] CRAN (R 3.6.0)                    
#>  cli           1.1.0     2019-03-19 [1] CRAN (R 3.6.0)                    
#>  crayon        1.3.4     2017-09-16 [1] CRAN (R 3.6.0)                    
#>  digest        0.6.22    2019-10-21 [1] CRAN (R 3.6.0)                    
#>  evaluate      0.14      2019-05-28 [1] CRAN (R 3.6.0)                    
#>  highr         0.8       2019-03-20 [1] CRAN (R 3.6.0)                    
#>  htmltools     0.4.0     2019-10-04 [1] CRAN (R 3.6.0)                    
#>  ITKR          0.5.2     2019-11-05 [1] Github (stnava/ITKR@fe97efa)      
#>  knitr         1.24.3    2019-08-28 [1] Github (muschellij2/knitr@abcea3d)
#>  lattice       0.20-38   2018-11-04 [1] CRAN (R 3.6.0)                    
#>  magrittr      1.5       2014-11-22 [1] CRAN (R 3.6.0)                    
#>  Matrix        1.2-17    2019-03-22 [1] CRAN (R 3.6.0)                    
#>  Rcpp          1.0.3     2019-11-08 [1] CRAN (R 3.6.0)                    
#>  RcppEigen     0.3.3.5.0 2018-11-24 [1] CRAN (R 3.6.0)                    
#>  rlang         0.4.1     2019-10-24 [1] CRAN (R 3.6.0)                    
#>  rmarkdown     1.16      2019-10-01 [1] CRAN (R 3.6.0)                    
#>  sessioninfo   1.1.1     2018-11-05 [1] CRAN (R 3.6.0)                    
#>  stringi       1.4.3     2019-03-12 [1] CRAN (R 3.6.0)                    
#>  stringr       1.4.0     2019-02-10 [1] CRAN (R 3.6.0)                    
#>  withr         2.1.2     2018-03-15 [1] CRAN (R 3.6.0)                    
#>  xfun          0.11      2019-11-12 [1] CRAN (R 3.6.0)                    
#>  yaml          2.2.0     2018-07-25 [1] CRAN (R 3.6.0)                    
#> 
#> [1] /Library/Frameworks/R.framework/Versions/3.6/Resources/library

Expected behavior
2D binary image returned.

Desktop (please complete the following information):

• OS: OSX Mojave