separate read and download tile capabilities

[mdsumner]

do any reading straight from the sources with GDAL, way better - ceramic probably just of historical interest

https://gist.github.com/mdsumner/92485d4f6cc198f59d1648e7ee25120f

x <- vapour:::vapour_tilexyz("https://api.mapbox.com/v4/mapbox.terrain-rgb/${z}/${x}/${y}.pngraw?access_token=YOURTOKEN", 
                             tile_level = 15)

writeLines(x)  ## let's add the http error codes for empty blocks
x <- '<GDAL_WMS>
    <Service name="TMS">
        <ServerUrl>https://api.mapbox.com/v4/mapbox.terrain-rgb/${z}/${x}/${y}.pngraw?access_token=YOURTOKEN</ServerUrl>
    </Service>
    <DataWindow>
        <UpperLeftX>-20037508.340000</UpperLeftX>
        <UpperLeftY>20037508.340000</UpperLeftY>
        <LowerRightX>20037508.340000</LowerRightX>
        <LowerRightY>-20037508.340000</LowerRightY>
        <TileLevel>15</TileLevel>
        <TileCountX>1</TileCountX>
        <TileCountY>1</TileCountY>
        <YOrigin>top</YOrigin>
    </DataWindow>
    <Projection>EPSG:3857</Projection>
    <BlockSizeX>256</BlockSizeX>
    <BlockSizeY>256</BlockSizeY>
    <BandsCount>3</BandsCount>
    <ZeroBlockHttpCodes>404</ZeroBlockHttpCodes> 
    <UserAgent>RStudio Server (2022.7.0.548); R (4.2.1 x86_64-pc-linux-gnu x86_64 linux-gnu)</UserAgent>
</GDAL_WMS>'
  
library(whatarelief)
ex <- c(-1, 1, -1, 1) * 4e5
prj <- "+proj=laea +lon_0=147 +lat_0=-42"
dm <- c(1024, 1024)
arr <- array(unlist(lapply(1:3, \(band) elevation(source = x, bands = band, extent = ex, dimension = dm, projection = prj)), 
                    use.names = FALSE), c(dm, 3L))

#https://docs.mapbox.com/data/tilesets/reference/mapbox-terrain-rgb-v1/#elevation-data

height = -10000 + ((arr[,,1] * 256 * 256 + arr[,,2] * 256 + arr[,,3]) * 0.1)
ximage::ximage(height, extent = ex, asp = 1, col = grey.colors(64), zlim = c(0, max(height)))

[mdsumner]

Actually, I think a better idea will be to keep the read capability, but just decouple it.

We can use vapour here and we can drop rgdal and raster.

[mdsumner]

this is in progress in branch use-gdal

[mdsumner]

done