Get Color Palette of Image using PowerShell - windows

Question

I am trying to get the Color Palette of an image. I tried various methods, and now I use the following code in PowerShell, but I could not get the correct result:
$filename = "C:\Users\schoo\Desktop\bb.jpg"
$BitMap = [System.Drawing.Bitmap]::FromFile((Get-Item $filename).fullname)
Foreach($y in (1..($BitMap.Height-1))){
Foreach($x in (1..($BitMap.Width-1))){
$Pixel = $BitMap.GetPixel($X,$Y)
$BackGround = $Pixel.Name
}
$R = $Pixel | select -ExpandProperty R
$G = $Pixel | select -ExpandProperty G
$B = $Pixel | select -ExpandProperty B
$A = $Pixel | select -ExpandProperty A
$allClr = "$R" + "." + "$G" + "." + "$B" + "." + "$A"
$allClr
}
The result take me more than thousand RGB codes:

Answer 1

I assume that by "color palette" you mean the swathe of distinct colours that appear in the image.
A simple (and quite fast) way to select only a distinct subset of a collection is to use a hashtable.
$filename = 'C:\Users\schoo\Desktop\bb.jpg'
$BitMap = [System.Drawing.Bitmap]::FromFile((Resolve-Path $filename).ProviderPath)
# A hashtable to keep track of the colors we've encountered
$table = #{}
foreach($h in 1..$BitMap.Height){
foreach($w in 1..$BitMap.Width) {
# Assign a value to the current Color key
$table[$BitMap.GetPixel($w - 1,$h - 1)] = $true
}
}
# The hashtable keys is out palette
$palette = $table.Keys