# Load the exported picture list from cPicture bilder.xml
[xml]$pictureXML = New-Object xml
$pictureXML.Load("$PSScriptRoot\blog\bilder.xml")

$picturesEVxml = @()

# Get the picture exposure data from the xml file.
$pictureXML.List.Picture | ForEach-Object { 
    # File="DSC_4121.JPG" Aperture="f/4,0" Shutterspeed="1/250s" Iso="ISO 320/26°"
    if ($_.Aperture -match "f/(\d(?:,\d+)?)") {
        $Aperture = [double]($matches[1].Replace(",", "."))

        if ($_.Shutterspeed -match "1/(\d+)s") {
            $Shutterspeed = [double]($matches[1])

            if ($_.Iso -match "ISO (\d+)(?:/d+°)?") {
                $Iso = [double]($matches[1])

                $picturesEVxml += ,@($($_.File), $Shutterspeed, $Aperture, $Iso)
            }
        }
    }
}

# Set up the list of pictures with the exposure settings.
$picturesEVlist = @(
    # Name, Speed, Aperture, ISO
    @("DSC_4121.NEF", 250, 4.0, 320),
    @("DSC_4122.NEF", 250, 5.0, 200),
    @("DSC_4123.NEF", 250, 5.6, 110),
    @("DSC_4124.NEF", 250, 4.0, 360),
    @("DSC_4125.NEF", 250, 5.0, 200),
    @("DSC_4126.NEF", 250, 5.6, 180),
    @("DSC_4127.NEF", 250, 5.6, 160),
    @("DSC_4128.NEF", 250, 4.0, 250),
    @("DSC_4129.NEF", 250, 5.0, 200),
    @("DSC_4130.NEF", 250, 5.6, 140),
    @("DSC_4131.NEF", 250, 5.6, 125)
)

#$picturesEV = $picturesEVlist
$picturesEV = $picturesEVxml

# Set the reference picture to which all other pictures will be aligned to.
$refPictureName = "DSC_4131.JPG"

# Get the data for the reference picture.
foreach ($pictureEV in $picturesEV) {
    if ($refPictureName -eq $pictureEV[0]) { 
        $refPictureEV = $pictureEV
        break
    } 
}

function log2([double]$x) {
    [Math]::Log($x) / [Math]::Log(2.0)
}

function Get-ExposureText($EV) {
    "1/$($EV[1])s f/$($EV[2]) ISO$($EV[3])"
}

[string]$expRef = Get-ExposureText $refPictureEV

"Adjust exposure to match $refPictureName [$expRef]:"

# Calulate the exposure correction for each picture.
foreach ($pictureEV in $picturesEV) {

    [string]$name = $pictureEV[0]

    # Example a to b:
    # 1/(250) to 1/(500) = -1EV , (log2 250) - (log2 500)
    # f5.6 to f4 = +1EV , 2*((log2 5.6) - (log2 4))
    # ISO200 to ISO100 = -1EV , (log2 100) - (log2 200)

    # Calulate correction values from speed, f-stop and iso.
    [double]$speedEV = (log2 $pictureEV[1]) - (log2 $refPictureEV[1])
    [double]$fEV = 2 * ((log2 $pictureEV[2]) - (log2 $refPictureEV[2]))
    [double]$isoEV = (log2 $refPictureEV[3]) - (log2 $pictureEV[3])

    [double]$EV = [math]::Round($speedEV + $fEV + $isoEV, 2)
    [string]$sign = if ($eV -gt 0.0) { "+" } else { "" }
    [string]$exp = Get-ExposureText $pictureEV

    # Output result.
    "$name [$exp] = $sign{0:g2}EV" -f $EV
}