Now I can edit map data in a text editor

PokemonRedMapTools.ps1

#Use examples:
#Get-Content route1.blk | MapBytesToText -Width 10
#(Invoke-WebRequest https://raw.githubusercontent.com/pret/pokeyellow/master/maps/route1.blk).Content | MapBytesToText -Width 10

#Takes .blk files and outputs a table of tile block indexes I can actually work with
#The resulting format can be eaten by MapBytesToText to convert back into .blk
function MapBytesToText {
    param([Parameter(Mandatory=$True,Position=1,ValueFromPipeline=$True)][String]$File,
        [Parameter(Mandatory=$False)][Int]$Width)
    $Width = $Width*4
    $formattedbytes = ([System.Text.Encoding]::UTF8.GetBytes($File)) | Foreach-Object {$_.toString().PadLeft(3," ")}
    $formattedbytes = $formattedbytes -join ','
    if($Width) {$formattedbytes = $formattedbytes -replace "(.{$Width})","`$1`n"}
    $formattedbytes
}


#Takes a formatted string of tile block indexes e.g.
# 10,78,86,86,86,77,
# 10,78,13,13,13,77
# as produced by MapBytesToText and converts for output to e.g. a .blk file
function MapStringToBytes {
    param([Parameter(Mandatory=$True,Position=1,ValueFromPipeline=$True)][String]$In)
    [System.Text.Encoding]::UTF8.GetString(($In -replace "[ `n]", "") -split ',')
}


#If there are no bugs, this flow should produce identical files.
#$mapdata = (Invoke-WebRequest https://raw.githubusercontent.com/pret/pokeyellow/master/maps/route1.blk).Content 
#$mapdata | MapBytesToText -Width 10 | MapStringToBytes | Out-File route1.blk