Define 'nchannels' and 'channel' for 'GeoTIFFImage'

src/GeoTIFF.jl

@@ -11,6 +11,7 @@ using StaticArrays: SVector, SMatrix, SA
 using FixedPointNumbers: Fixed, Normed
 
 import TiffImages
+import TiffImages: nchannels, channel
 
 include("geokeys.jl")
 include("metadata.jl")

src/image.jl

@@ -18,17 +18,31 @@ end
 """
     GeoTIFF.tiff(geotiff)
 
-TIFF image of a `geotiff` image.
+TIFF image of the `geotiff` image.
 """
 tiff(geotiff::GeoTIFFImage) = geotiff.tiff
 
 """
     GeoTIFF.metadata(geotiff)
 
-GeoTIFF metadata of a `geotiff` image.
+GeoTIFF metadata of the `geotiff` image.
 """
 metadata(geotiff::GeoTIFFImage) = geotiff.metadata
 
+"""
+    GeoTIFF.nchannels(geotiff)
+
+Number of channels of the `geotiff` image.
+"""
+nchannels(geotiff::GeoTIFFImage) = nchannels(geotiff.tiff)
+
+"""
+    GeoTIFF.channel(geotiff, i)
+
+`i`'th channel of the `geotiff` image.
+"""
+channel(geotiff::GeoTIFFImage, i) = mappedarray(c -> channel(c, i), geotiff.tiff)
+
 # AbstractArray interface
 Base.size(geotiff::GeoTIFFImage) = size(geotiff.tiff)
 Base.getindex(geotiff::GeoTIFFImage, i...) = getindex(geotiff.tiff, i...)

test/runtests.jl

@@ -68,6 +68,21 @@ savedir = mktempdir()
     geotiff[1, 1] = color
     @test geotiff[1, 1] == color
     @test IndexStyle(geotiff) === IndexCartesian()
+
+    # multi-channel image
+    file = joinpath(savedir, "multi.tiff")
+    channel1 = rand(10, 10)
+    channel2 = rand(10, 10)
+    channel3 = rand(10, 10)
+    channel4 = rand(10, 10)
+    GeoTIFF.save(file, channel1, channel2, channel3, channel4)
+    geotiff = GeoTIFF.load(file)
+    @test eltype(geotiff) <: TiffImages.WidePixel
+    @test GeoTIFF.nchannels(geotiff) == 4
+    @test GeoTIFF.channel(geotiff, 1) == channel1
+    @test GeoTIFF.channel(geotiff, 2) == channel2
+    @test GeoTIFF.channel(geotiff, 3) == channel3
+    @test GeoTIFF.channel(geotiff, 4) == channel4
   end
 
   @testset "save" begin