[R-sig-Geo] rgdal, multiband CCITT compression

[Oliver Soong]

Here's an example:




require(rgdal)
formals(paste)$sep <- ""

SP27GTIF <- readGDAL(
  system.file("pictures/SP27GTIF.TIF", package = "rgdal")[1],
  output.dim=c(100,100)
)
img_1bit_1band <- SP27GTIF
img_1bit_1band at data$band1 <- as.integer(SP27GTIF at data$band1 > 85)
img_1bit_2band <- SP27GTIF
img_1bit_2band at data <- data.frame(
  band1 = img_1bit_1band at data$band1,
  band2 = as.integer(SP27GTIF at data$band1 > 170)
)

for(img in c("img_1bit_1band", "img_1bit_2band")) {
  cat(paste("*** Correct Stats: ", img, "\n"))
  print(sapply(get(img)@data, table))
  for(compress in c("NONE", "DEFLATE", "LZW", "CCITTRLE",
                    "CCITTFAX3", "CCITTFAX4")) {
    file <- paste(img, "_", compress, ".tif")
    writeGDAL(get(img), file, type = "Byte",
      options = c("NBITS=1", paste("COMPRESS=", compress)))
    cat(paste("Compression: ", compress, " from ", file, "\n"))
    reread <- readGDAL(file, silent = TRUE)
    print(sapply(reread at data, table))
  }
  cat("\n")
}





The expected output is:

*** Correct Stats: img_1bit_1band
  band1
0  3086
1  6914
Compression: NONE from img_1bit_1band_NONE.tif
  band1
0  3086
1  6914
Compression: DEFLATE from img_1bit_1band_DEFLATE.tif
  band1
0  3086
1  6914
Compression: LZW from img_1bit_1band_LZW.tif
  band1
0  3086
1  6914
Compression: CCITTRLE from img_1bit_1band_CCITTRLE.tif
  band1
0  3086
1  6914
Compression: CCITTFAX3 from img_1bit_1band_CCITTFAX3.tif
  band1
0  3086
1  6914
Compression: CCITTFAX4 from img_1bit_1band_CCITTFAX4.tif
  band1
0  3086
1  6914

*** Correct Stats: img_1bit_2band
  band1 band2
0  3086  8353
1  6914  1647
Compression: NONE from img_1bit_2band_NONE.tif
  band1 band2
0  3086  8353
1  6914  1647
Compression: DEFLATE from img_1bit_2band_DEFLATE.tif
  band1 band2
0  3086  8353
1  6914  1647
Compression: LZW from img_1bit_2band_LZW.tif
  band1 band2
0  3086  8353
1  6914  1647
Compression: CCITTRLE from img_1bit_2band_CCITTRLE.tif
  band1 band2
0  6131  8783
1  3869  1217
Compression: CCITTFAX3 from img_1bit_2band_CCITTFAX3.tif
  band1 band2
0  6131  8783
1  3869  1217
Compression: CCITTFAX4 from img_1bit_2band_CCITTFAX4.tif
  band1 band2
0  6131  8783
1  3869  1217



Everything looks fine except CCITT compression with 2 bands.

I wasn't able to dig up Windows GDAL 1.7.1 binaries, and the 1.7.0
binaries from FW_Tools seem to give similar behavior, although it's a
little hard to check because neither ArcGIS nor ENVI seems to like any
of the multi-band files.