Phase 3: app icon (multi-resolution ICO + master PNG)

scripts/generate-icons.ps1 renders the icon programmatically with
System.Drawing - rounded teal square (#0E7C66) with a stylized white
hook glyph - at 16/24/32/48/64/128/256 px and assembles a proper
multi-resolution Microsoft ICO. The PNG and ICO outputs land in
resources/. The script is the source of truth; re-run after editing
the design.

GUI csproj uses ApplicationIcon for the EXE icon and embeds the .ico
+ .png as Resources so MainWindow and AboutDialog can use them via
WPF's resource URI scheme.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

scripts/generate-icons.ps1

@@ -0,0 +1,138 @@
+<#
+.SYNOPSIS
+    Generates webhook-server.ico (multi-resolution) and webhook-server.png from
+    a programmatic design. Re-run after changing Draw-Icon to refresh assets.
+
+.DESCRIPTION
+    Renders the icon at 16/24/32/48/64/128/256 px using System.Drawing, then
+    assembles a Microsoft-format ICO file with each size embedded as PNG. No
+    external tools required.
+
+    Design: a rounded-square teal background (#0E7C66) with a stylized white
+    hook shape (a "J"-like curve with an arrow tip).
+#>
+[CmdletBinding()]
+param(
+    [string]$OutputDir = (Join-Path $PSScriptRoot '..\resources')
+)
+
+$ErrorActionPreference = 'Stop'
+Add-Type -AssemblyName System.Drawing
+
+New-Item -ItemType Directory -Path $OutputDir -Force | Out-Null
+
+function New-IconBitmap([int]$size) {
+    $bmp = New-Object System.Drawing.Bitmap $size, $size, ([System.Drawing.Imaging.PixelFormat]::Format32bppArgb)
+    $g = [System.Drawing.Graphics]::FromImage($bmp)
+    $g.SmoothingMode = [System.Drawing.Drawing2D.SmoothingMode]::AntiAlias
+    $g.InterpolationMode = [System.Drawing.Drawing2D.InterpolationMode]::HighQualityBicubic
+    $g.PixelOffsetMode = [System.Drawing.Drawing2D.PixelOffsetMode]::HighQuality
+
+    # Background: rounded square in brand teal.
+    $bgColor = [System.Drawing.Color]::FromArgb(0xFF, 0x0E, 0x7C, 0x66)
+    $bgBrush = New-Object System.Drawing.SolidBrush $bgColor
+    $radius = [int]($size * 0.22)
+    $rect = New-Object System.Drawing.RectangleF 0, 0, $size, $size
+
+    $path = New-Object System.Drawing.Drawing2D.GraphicsPath
+    $d = $radius * 2
+    $path.AddArc($rect.X, $rect.Y, $d, $d, 180, 90)
+    $path.AddArc($rect.Right - $d, $rect.Y, $d, $d, 270, 90)
+    $path.AddArc($rect.Right - $d, $rect.Bottom - $d, $d, $d, 0, 90)
+    $path.AddArc($rect.X, $rect.Bottom - $d, $d, $d, 90, 90)
+    $path.CloseFigure()
+    $g.FillPath($bgBrush, $path)
+
+    # Foreground: white hook shape - a thick curved stroke shaped like a "J"
+    # tipped with an arrowhead, sized relative to the canvas.
+    $fgColor = [System.Drawing.Color]::White
+    $stroke = [Math]::Max(2, [int]($size * 0.12))
+    $pen = New-Object System.Drawing.Pen $fgColor, $stroke
+    $pen.StartCap = [System.Drawing.Drawing2D.LineCap]::Round
+    $pen.EndCap = [System.Drawing.Drawing2D.LineCap]::Round
+    $pen.LineJoin = [System.Drawing.Drawing2D.LineJoin]::Round
+
+    # Hook curve: vertical down-stroke on the right, then a half-circle arc
+    # curling to the left and ending in a small filled dot for the hook tip.
+    $cx     = [single]($size * 0.62)
+    $top    = [single]($size * 0.22)
+    $bottom = [single]($size * 0.58)
+    $arcD   = [single]($size * 0.34)        # arc diameter
+    $arcLeft = [single]($cx - $arcD)        # left edge of arc circle
+
+    # Vertical stroke from (cx, top) to (cx, bottom).
+    $g.DrawLine($pen, $cx, $top, $cx, $bottom)
+
+    # Half-circle arc beneath: starts at (cx, bottom), curls to (cx - arcD, bottom).
+    $arcRect = New-Object System.Drawing.RectangleF $arcLeft, ([single]($bottom - $arcD / 2)), $arcD, $arcD
+    $g.DrawArc($pen, $arcRect, 0, 180)
+
+    # Filled circle at the tip end of the arc.
+    $tipR = [single]($stroke * 0.6)
+    $tipX = $arcLeft
+    $tipY = [single]($bottom)
+    $brushFg = New-Object System.Drawing.SolidBrush $fgColor
+    $g.FillEllipse($brushFg, [single]($tipX - $tipR), [single]($tipY - $tipR), [single]($tipR * 2), [single]($tipR * 2))
+
+    $brushFg.Dispose(); $pen.Dispose(); $bgBrush.Dispose(); $path.Dispose()
+    $g.Dispose()
+    return $bmp
+}
+
+# Generate each size as PNG bytes. Hashtable keys are prefixed with "s" because
+# PowerShell hashtable lookups by integer key behave inconsistently with PSObject
+# wrapping; string keys round-trip cleanly.
+$sizes = @(16, 24, 32, 48, 64, 128, 256)
+$pngs = @{}
+foreach ($s in $sizes) {
+    $bmp = New-IconBitmap $s
+    $ms = New-Object System.IO.MemoryStream
+    $bmp.Save($ms, [System.Drawing.Imaging.ImageFormat]::Png)
+    $pngs["s$s"] = $ms.ToArray()
+    $ms.Dispose()
+    $bmp.Dispose()
+}
+
+# Save the master 256 PNG separately for places that need a transparent PNG.
+$pngPath = Join-Path $OutputDir 'webhook-server.png'
+[System.IO.File]::WriteAllBytes($pngPath, [byte[]]$pngs['s256'])
+
+# Assemble multi-resolution ICO.
+$icoPath = Join-Path $OutputDir 'webhook-server.ico'
+$ms = New-Object System.IO.MemoryStream
+$bw = New-Object System.IO.BinaryWriter $ms
+try {
+    $count = $sizes.Count
+    $bw.Write([UInt16]0)            # idReserved
+    $bw.Write([UInt16]1)            # idType: 1 = ICO
+    $bw.Write([UInt16]$count)       # idCount
+
+    # Directory entries (16 bytes each).
+    $offset = 6 + 16 * $count
+    foreach ($s in $sizes) {
+        $bytes = $pngs["s$s"]
+        $w = if ($s -ge 256) { 0 } else { $s }
+        $h = if ($s -ge 256) { 0 } else { $s }
+        $bw.Write([byte]$w)         # width
+        $bw.Write([byte]$h)         # height
+        $bw.Write([byte]0)          # colorCount
+        $bw.Write([byte]0)          # reserved
+        $bw.Write([UInt16]1)        # planes
+        $bw.Write([UInt16]32)       # bitCount
+        $bw.Write([UInt32]$bytes.Length)
+        $bw.Write([UInt32]$offset)
+        $offset += $bytes.Length
+    }
+
+    # Image data.
+    foreach ($s in $sizes) { $bw.Write($pngs["s$s"]) }
+
+    $bw.Flush()
+    [System.IO.File]::WriteAllBytes($icoPath, $ms.ToArray())
+}
+finally {
+    $bw.Dispose(); $ms.Dispose()
+}
+
+Write-Host "Wrote $icoPath ($((Get-Item $icoPath).Length) bytes)"
+Write-Host "Wrote $pngPath ($((Get-Item $pngPath).Length) bytes)"

src/WebhookServer.Gui/MainWindow.xaml

@@ -7,6 +7,7 @@
         xmlns:models="clr-namespace:WebhookServer.Core.Models;assembly=WebhookServer.Core"
         mc:Ignorable="d"
         Title="Webhook Server" Height="600" Width="1000"
+        Icon="/webhook-server.ico"
         d:DataContext="{d:DesignInstance Type=vm:MainViewModel}">
     <Window.InputBindings>
         <KeyBinding Key="N" Modifiers="Control" Command="{Binding AddEndpointCommand}"/>

src/WebhookServer.Gui/Views/AboutDialog.xaml

@@ -2,9 +2,10 @@
         xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
         xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
         Title="About Webhook Server"
-        Height="320" Width="420"
+        Height="360" Width="440"
         ResizeMode="NoResize"
         WindowStartupLocation="CenterOwner"
+        Icon="/webhook-server.ico"
         ShowInTaskbar="False">
     <Grid Margin="20">
         <Grid.RowDefinitions>

src/WebhookServer.Gui/WebhookServer.Gui.csproj

@@ -14,6 +14,13 @@
     <Nullable>enable</Nullable>
     <ImplicitUsings>enable</ImplicitUsings>
     <UseWPF>true</UseWPF>
+    <ApplicationIcon>..\..\resources\webhook-server.ico</ApplicationIcon>
+    <AssemblyTitle>Webhook Server</AssemblyTitle>
   </PropertyGroup>
 
+  <ItemGroup>
+    <Resource Include="..\..\resources\webhook-server.ico" Link="webhook-server.ico" />
+    <Resource Include="..\..\resources\webhook-server.png" Link="webhook-server.png" />
+  </ItemGroup>
+
 </Project>