ashen-realms/tools/derive-monster-assets.ps1

# tools/derive-monster-assets.ps1
# Derives the web assets each monster needs from the hand-made art in
# art/enemies and art/backgrounds.
#
# Per monster it writes four files:
#   apps/web/public/images/monsters/<key>.png            full painted artwork
#   apps/web/public/images/monsters/runtime/<key>-560.jpg downscaled for the web
#   apps/web/public/images/combat/sprites/<key>-<h>.png  background-free cutout
#   apps/web/public/images/combat/icons/<key>-128.png    medallion icon
#
# The generated files are committed, so this only needs re-running when the
# source art changes. Re-runnable: it overwrites its own output and touches
# nothing else.
$ErrorActionPreference = 'Stop'
Add-Type -AssemblyName System.Drawing

$root = Split-Path -Parent $PSScriptRoot
$artEnemies = Join-Path $root 'art\enemies'
$artCutouts = Join-Path $artEnemies 'transparent-background'
$artBackgrounds = Join-Path $root 'art\backgrounds'
$webImages = Join-Path $root 'apps\web\public\images'

foreach ($dir in @(
    (Join-Path $webImages 'monsters\runtime'),
    (Join-Path $webImages 'combat\sprites'),
    (Join-Path $webImages 'combat\icons'),
    (Join-Path $webImages 'backgrounds\runtime'))) {
  New-Item -ItemType Directory -Force -Path $dir | Out-Null
}

function Save-Scaled {
  param(
    [string] $SourcePath,
    [string] $TargetPath,
    [int] $TargetWidth,
    [string] $Format,
    [switch] $Opaque
  )
  $img = [System.Drawing.Image]::FromFile($SourcePath)
  try {
    $height = [int][Math]::Round($img.Height * $TargetWidth / $img.Width)
    $bitmap = New-Object System.Drawing.Bitmap $TargetWidth, $height
    $graphics = [System.Drawing.Graphics]::FromImage($bitmap)
    if ($Opaque) {
      $graphics.Clear([System.Drawing.Color]::Black)
    }
    $graphics.InterpolationMode = [System.Drawing.Drawing2D.InterpolationMode]::HighQualityBicubic
    $graphics.DrawImage($img, 0, 0, $TargetWidth, $height)
    $graphics.Dispose()
    if ($Format -eq 'jpg') {
      $codec = [System.Drawing.Imaging.ImageCodecInfo]::GetImageEncoders() |
        Where-Object { $_.MimeType -eq 'image/jpeg' }
      $params = New-Object System.Drawing.Imaging.EncoderParameters 1
      $params.Param[0] = New-Object System.Drawing.Imaging.EncoderParameter(
        [System.Drawing.Imaging.Encoder]::Quality, 82)
      $bitmap.Save($TargetPath, $codec, $params)
    }
    else {
      $bitmap.Save($TargetPath, [System.Drawing.Imaging.ImageFormat]::Png)
    }
    $bitmap.Dispose()
  }
  finally {
    $img.Dispose()
  }
  Write-Host "wrote $(Split-Path -Leaf $TargetPath)"
}

function Save-Icon {
  param(
    [string] $SourcePath,
    [string] $TargetPath,
    # Crop window as fractions of the source, chosen per monster so the icon
    # lands on the head rather than on whatever the centre happens to be.
    [double] $CropX, [double] $CropY, [double] $CropSize
  )
  $img = [System.Drawing.Image]::FromFile($SourcePath)
  try {
    $side = [int]([Math]::Min($img.Width, $img.Height) * $CropSize)
    $x = [int]($img.Width * $CropX)
    $y = [int]($img.Height * $CropY)
    $bitmap = New-Object System.Drawing.Bitmap 128, 128
    $graphics = [System.Drawing.Graphics]::FromImage($bitmap)
    $graphics.InterpolationMode = [System.Drawing.Drawing2D.InterpolationMode]::HighQualityBicubic
    $graphics.DrawImage(
      $img,
      (New-Object System.Drawing.Rectangle 0, 0, 128, 128),
      (New-Object System.Drawing.Rectangle $x, $y, $side, $side),
      [System.Drawing.GraphicsUnit]::Pixel)
    $graphics.Dispose()
    $bitmap.Save($TargetPath, [System.Drawing.Imaging.ImageFormat]::Png)
    $bitmap.Dispose()
  }
  finally {
    $img.Dispose()
  }
  Write-Host "wrote $(Split-Path -Leaf $TargetPath)"
}

# `source` is the painted file, `cutout` the background-free one.
#
# NOTE the deliberate crossing on the first two rows: the file named
# raider-scout depicts the heavier, plated, spear-carrying figure and is the
# Veteran; raider-veteran depicts the leaner one and is the Scout. Slice 0.10
# design decision D7.
$monsters = @(
  @{ key = 'raider-scout';   source = 'raider-veteran'; spriteHeight = 620; cropX = 0.40; cropY = 0.04; cropSize = 0.30 },
  @{ key = 'raider-veteran'; source = 'raider-scout';   spriteHeight = 620; cropX = 0.40; cropY = 0.04; cropSize = 0.30 },
  @{ key = 'burned-hound';   source = 'burned-hound';   spriteHeight = 760; cropX = 0.06; cropY = 0.12; cropSize = 0.34 },
  @{ key = 'raider-captain'; source = 'Pluendererhauptmann'; spriteHeight = 620; cropX = 0.36; cropY = 0.02; cropSize = 0.28 }
)

foreach ($monster in $monsters) {
  $key = $monster.key
  $painted = Join-Path $artEnemies "$($monster.source).png"
  $cutout = Join-Path $artCutouts "$($monster.source).png"

  Copy-Item -Force $painted (Join-Path $webImages "monsters\$key.png")
  Write-Host "wrote $key.png"

  Save-Scaled -SourcePath $painted `
    -TargetPath (Join-Path $webImages "monsters\runtime\$key-560.jpg") `
    -TargetWidth 560 -Format 'jpg' -Opaque

  Save-Scaled -SourcePath $cutout `
    -TargetPath (Join-Path $webImages "combat\sprites\$key-$($monster.spriteHeight).png") `
    -TargetWidth $monster.spriteHeight -Format 'png'

  # The Raider Captain's icon comes from hand-made art below, not a generated
  # crop of the body art, so skip the crop step for that key here.
  if ($key -ne 'raider-captain') {
    Save-Icon -SourcePath $cutout `
      -TargetPath (Join-Path $webImages "combat\icons\$key-128.png") `
      -CropX $monster.cropX -CropY $monster.cropY -CropSize $monster.cropSize
  }
}

# The Raider Captain has a hand-made icon. Authored art beats a generated
# crop, but it still has to ship at icon size: resize the 1254x1254 source
# down to 128x128 rather than copying it verbatim. It's already a square
# portrait, so a straight bicubic resize preserves the authored composition
# with no re-cropping.
Save-Scaled -SourcePath (Join-Path $artEnemies 'PluendererhauptmannIcon.png') `
  -TargetPath (Join-Path $webImages 'combat\icons\raider-captain-128.png') `
  -TargetWidth 128 -Format 'png'

foreach ($background in 'Wachturm', 'Aschengrube') {
  $source = Join-Path $artBackgrounds "$background.png"
  Copy-Item -Force $source (Join-Path $webImages "backgrounds\$background.png")
  Write-Host "wrote $background.png"
  Save-Scaled -SourcePath $source `
    -TargetPath (Join-Path $webImages "backgrounds\runtime\$background-960.jpg") `
    -TargetWidth 960 -Format 'jpg' -Opaque
}