Get Cats

#Prompt for how many cat pictures we're going to retrieve
$cats = Read-Host -Prompt 'Input how many cats you want'

#start the loop
For ($i=1; $i -le $cats; $i++)
{
    #set the filename. This will be useful
    $Filename = "Cat $i"

    #store the file with a temporary name
    Invoke-WebRequest "https://api.thecatapi.com/api/images/get?format=src&results_per_page=1" -OutFile "$Filename"

    #open the file as binary so we can check the header to determine the file type
    $a = [System.IO.File]::ReadAllBytes("$Filename");

    #read the relevant bits for GIF
    $header = "{0:X2}" -f $a[0]
    $header += "{0:X2}" -f $a[1]
    $header += "{0:X2}" -f $a[2]

    #check if the header says it's a GIF
    If ($header -eq "474946") {
        #If it is, tell the user the filename and move the temporary file to the correct name
        Write-Host "$Filename.gif"
        Move-Item -Path $Filename -Destination "$Filename.gif"
    }

    #read the relevant bits for JPG (JFIF)
    $header = "{0:X2}" -f $a[6]
    $header += "{0:X2}" -f $a[7]
    $header += "{0:X2}" -f $a[8]
    $header += "{0:X2}" -f $a[9]

    #check if the header says "JFIF"
    If ($header -eq "4A464946") {
        #If it is, tell the user the filename and move the temporary file to the correct name
        Write-Host "$Filename.jpg"
        Move-Item -Path $Filename -Destination "$Filename.jpg"
     }

     #read the relevant bits for PNG
     $header = "{0:X2}" -f $a[1]
     $header += "{0:X2}" -f $a[2]
     $header += "{0:X2}" -f $a[3]

     #check if the header says "PNG"
     If ($header -eq "504E47") {
        #If it is, tell the user the filename and move the temporary file to the correct name
        Write-Host "$Filename.png"
        Move-Item -Path $Filename -Destination "$Filename.png"
     }
}