MCP Screenshot Server

/** * WSL capture engine implementation * Uses powershell.exe to capture Windows host screen from WSL */ import { exec } from "child_process"; import { promisify } from "util"; import { BaseCaptureEngine } from "./base-capture-engine"; import { DisplayInfo, WindowInfo } from "../types"; import { CaptureFailedError, DisplayNotFoundError, WindowNotFoundError, } from "../errors"; const execAsync = promisify(exec); /** * WSL-specific capture engine */ export class WSLCaptureEngine extends BaseCaptureEngine { /** * Execute a PowerShell command on the Windows host */ private async runPowerShell(command: string): Promise<string> { // Escape double quotes for the shell // AND escape $ signs so the Linux shell doesn't expand them const escapedCommand = command .replace(/"/g, '\\"') .replace(/\$/g, "\\$") .replace(/`/g, "\\`"); // Also escape backticks just in case // Use powershell.exe from Windows // Increase maxBuffer to 50MB to handle large base64 image output const { stdout, stderr } = await execAsync( `powershell.exe -NoProfile -NonInteractive -Command "${escapedCommand}"`, { maxBuffer: 50 * 1024 * 1024, shell: "/bin/bash", // Use bash which has Windows paths in WSL } ); if (stderr && !stderr.includes("CLM")) { // console.warn("PowerShell stderr:", stderr); } return stdout.trim(); } /** * Capture full screen or specific display */ async captureScreen(displayId?: string): Promise<Buffer> { try { const script = ` # Try to set DPI awareness to capture full resolution try { $user32 = Add-Type -MemberDefinition '[DllImport("user32.dll")] public static extern bool SetProcessDPIAware();' -Name "User32" -Namespace Win32 -PassThru $user32::SetProcessDPIAware() | Out-Null } catch { # Ignore if already set or fails } Add-Type -AssemblyName System.Windows.Forms Add-Type -AssemblyName System.Drawing $screens = [System.Windows.Forms.Screen]::AllScreens $screen = $null if ("${displayId}" -ne "") { $screen = $screens | Where-Object { $_.DeviceName -eq "${displayId}" } } if ($null -eq $screen) { $screen = [System.Windows.Forms.Screen]::PrimaryScreen } $bitmap = New-Object System.Drawing.Bitmap $screen.Bounds.Width, $screen.Bounds.Height $graphics = [System.Drawing.Graphics]::FromImage($bitmap) $graphics.CopyFromScreen($screen.Bounds.X, $screen.Bounds.Y, 0, 0, $bitmap.Size) $ms = New-Object System.IO.MemoryStream $bitmap.Save($ms, [System.Drawing.Imaging.ImageFormat]::Png) [Convert]::ToBase64String($ms.ToArray()) `; const base64 = await this.runPowerShell(script); if (!base64) { throw new Error("Empty output from PowerShell"); } return Buffer.from(base64, "base64"); } catch (error) { throw new CaptureFailedError( `Failed to capture screen: ${(error as Error).message}`, { displayId, error } ); } } /** * Capture a specific window */ async captureWindow( windowId: string, includeFrame: boolean ): Promise<Buffer> { try { const script = ` # Try to set DPI awareness try { $user32 = Add-Type -MemberDefinition '[DllImport("user32.dll")] public static extern bool SetProcessDPIAware();' -Name "User32" -Namespace Win32 -PassThru $user32::SetProcessDPIAware() | Out-Null } catch { # Ignore } Add-Type -TypeDefinition @" using System; using System.Runtime.InteropServices; public struct RECT { public int Left; public int Top; public int Right; public int Bottom; } public struct POINT { public int X; public int Y; } public class User32 { [DllImport("user32.dll")] public static extern bool GetWindowRect(IntPtr hwnd, out RECT lpRect); [DllImport("user32.dll")] public static extern bool GetClientRect(IntPtr hwnd, out RECT lpRect); [DllImport("user32.dll")] public static extern bool ClientToScreen(IntPtr hwnd, ref POINT lpPoint); [DllImport("user32.dll")] public static extern bool IsIconic(IntPtr hwnd); } "@ | Out-Null $hwnd = [IntPtr]${windowId} if ([User32]::IsIconic($hwnd)) { throw "Window is minimized" } $x = 0 $y = 0 $width = 0 $height = 0 if ($${includeFrame}) { $rect = New-Object RECT [User32]::GetWindowRect($hwnd, [ref]$rect) | Out-Null $x = $rect.Left $y = $rect.Top $width = $rect.Right - $rect.Left $height = $rect.Bottom - $rect.Top } else { $rect = New-Object RECT [User32]::GetClientRect($hwnd, [ref]$rect) | Out-Null $pt = New-Object POINT $pt.X = 0 $pt.Y = 0 [User32]::ClientToScreen($hwnd, [ref]$pt) | Out-Null $x = $pt.X $y = $pt.Y $width = $rect.Right $height = $rect.Bottom } if ($width -le 0 -or $height -le 0) { throw "Invalid window dimensions" } Add-Type -AssemblyName System.Drawing | Out-Null $bitmap = New-Object System.Drawing.Bitmap $width, $height $graphics = [System.Drawing.Graphics]::FromImage($bitmap) $graphics.CopyFromScreen($x, $y, 0, 0, $bitmap.Size) $ms = New-Object System.IO.MemoryStream $bitmap.Save($ms, [System.Drawing.Imaging.ImageFormat]::Png) [Convert]::ToBase64String($ms.ToArray()) `; const base64 = await this.runPowerShell(script); return Buffer.from(base64, "base64"); } catch (error) { const message = (error as Error).message; if (message.includes("Window is minimized")) { throw new WindowNotFoundError( `Cannot capture minimized window ${windowId}`, { windowId, isMinimized: true } ); } throw new CaptureFailedError(`Failed to capture window: ${message}`, { windowId, error, }); } } /** * Capture a specific region */ protected async captureRegionInternal( x: number, y: number, width: number, height: number ): Promise<Buffer> { try { const script = ` # Try to set DPI awareness try { $user32 = Add-Type -MemberDefinition '[DllImport("user32.dll")] public static extern bool SetProcessDPIAware();' -Name "User32" -Namespace Win32 -PassThru $user32::SetProcessDPIAware() | Out-Null } catch { # Ignore } Add-Type -AssemblyName System.Windows.Forms Add-Type -AssemblyName System.Drawing $bitmap = New-Object System.Drawing.Bitmap ${width}, ${height} $graphics = [System.Drawing.Graphics]::FromImage($bitmap) $graphics.CopyFromScreen(${x}, ${y}, 0, 0, $bitmap.Size) $ms = New-Object System.IO.MemoryStream $bitmap.Save($ms, [System.Drawing.Imaging.ImageFormat]::Png) [Convert]::ToBase64String($ms.ToArray()) `; const base64 = await this.runPowerShell(script); return Buffer.from(base64, "base64"); } catch (error) { throw new CaptureFailedError( `Failed to capture region: ${(error as Error).message}`, { x, y, width, height, error } ); } } /** * Get list of connected displays */ async getDisplays(): Promise<DisplayInfo[]> { try { const script = ` Add-Type -TypeDefinition @" using System; using System.Runtime.InteropServices; public class User32 { [DllImport("user32.dll")] public static extern bool SetProcessDPIAware(); } "@ | Out-Null [User32]::SetProcessDPIAware() | Out-Null Add-Type -AssemblyName System.Windows.Forms | Out-Null [System.Windows.Forms.Screen]::AllScreens | ForEach-Object { @{ id = $_.DeviceName name = $_.DeviceName x = $_.Bounds.X y = $_.Bounds.Y width = $_.Bounds.Width height = $_.Bounds.Height primary = $_.Primary } } | ConvertTo-Json `; const json = await this.runPowerShell(script); const data = JSON.parse(json); const screens = Array.isArray(data) ? data : [data]; return screens.map((s: any) => ({ id: s.id, name: s.name, resolution: { width: s.width, height: s.height, }, position: { x: s.x, y: s.y, }, isPrimary: s.primary, })); } catch (error) { // Fallback to default if detection fails return [ { id: "default", name: "Default Display", resolution: { width: 1920, height: 1080 }, position: { x: 0, y: 0 }, isPrimary: true, }, ]; } } /** * Get list of visible windows */ async getWindows(): Promise<WindowInfo[]> { try { const script = ` Add-Type -TypeDefinition @" using System; using System.Runtime.InteropServices; public struct RECT { public int Left; public int Top; public int Right; public int Bottom; } public class User32 { [DllImport("user32.dll")] public static extern bool GetWindowRect(IntPtr hwnd, out RECT lpRect); [DllImport("user32.dll")] public static extern bool IsIconic(IntPtr hwnd); [DllImport("user32.dll")] public static extern bool SetProcessDPIAware(); } "@ | Out-Null [User32]::SetProcessDPIAware() | Out-Null Get-Process | Where-Object { $_.MainWindowTitle -ne "" } | ForEach-Object { $hwnd = $_.MainWindowHandle $rect = New-Object RECT [User32]::GetWindowRect($hwnd, [ref]$rect) $isMinimized = [User32]::IsIconic($hwnd) @{ id = $hwnd.ToString() title = $_.MainWindowTitle processId = $_.Id processName = $_.ProcessName x = $rect.Left y = $rect.Top width = $rect.Right - $rect.Left height = $rect.Bottom - $rect.Top isMinimized = $isMinimized } } | ConvertTo-Json `; const json = await this.runPowerShell(script); // Handle empty or single object result if (!json) return []; const data = JSON.parse(json); const windows = Array.isArray(data) ? data : [data]; return windows .filter((w: any) => typeof w === "object" && w !== null && w.id) .map((w: any) => ({ id: String(w.id), title: w.title, pid: w.processId, processName: w.processName, bounds: { x: w.x || 0, y: w.y || 0, width: w.width || 0, height: w.height || 0, }, isMinimized: !!w.isMinimized, })); } catch (error) { return []; } } /** * Get window by ID */ async getWindowById(windowId: string): Promise<WindowInfo | null> { const windows = await this.getWindows(); return windows.find((w) => w.id === windowId) || null; } /** * Get window by title pattern */ async getWindowByTitle(titlePattern: string): Promise<WindowInfo | null> { const windows = await this.getWindows(); const regex = new RegExp(titlePattern, "i"); return windows.find((w) => regex.test(w.title)) || null; } }