How do you take a Screenshot of a website via .Net code?

Question

Is it possible to take a screen shot of any given url using .Net code?

What is the easiest way to do it?

Answer 1

I'd suggest using a third-party approach for this, not doing it yourself. If you insist, though, then the heavy-handed way is to use System.Diagnostics.Process to launch a browser, then GetDesktopImage to get a screenshot.

I'm sure there's an easier way, but that looks like this:

using System;
using System.Drawing;
using System.Drawing.Imaging;
using System.Runtime.InteropServices;

public class PlatformInvokeGDI32
{
    public  const int SRCCOPY = 13369376;

    [DllImport("gdi32.dll",EntryPoint="DeleteDC")]
    public static extern IntPtr DeleteDC(IntPtr hDc);

    [DllImport("gdi32.dll",EntryPoint="DeleteObject")]
    public static extern IntPtr DeleteObject(IntPtr hDc);

    [DllImport("gdi32.dll",EntryPoint="BitBlt")]
    public static extern bool BitBlt(IntPtr hdcDest, int xDest, int yDest, int wDest, int hDest, IntPtr hdcSource, int xSrc, int ySrc, int RasterOp);

    [DllImport ("gdi32.dll",EntryPoint="CreateCompatibleBitmap")]
    public static extern IntPtr CreateCompatibleBitmap(IntPtr hdc,int nWidth, int nHeight);

    [DllImport ("gdi32.dll",EntryPoint="CreateCompatibleDC")]
    public static extern IntPtr CreateCompatibleDC(IntPtr hdc);

    [DllImport ("gdi32.dll",EntryPoint="SelectObject")]
    public static extern IntPtr SelectObject(IntPtr hdc,IntPtr bmp);
}

public class PlatformInvokeUSER32
{
    public const int SM_CXSCREEN = 0;
    public const int SM_CYSCREEN = 1;

    [DllImport("user32.dll", EntryPoint="GetDesktopWindow")]
    public static extern IntPtr GetDesktopWindow();

    [DllImport("user32.dll",EntryPoint="GetDC")]
    public static extern IntPtr GetDC(IntPtr ptr);

    [DllImport("user32.dll",EntryPoint="GetSystemMetrics")]
    public static extern int GetSystemMetrics(int abc);

    [DllImport("user32.dll",EntryPoint="GetWindowDC")]
    public static extern IntPtr GetWindowDC(Int32 ptr);

    [DllImport("user32.dll",EntryPoint="ReleaseDC")]
    public static extern IntPtr ReleaseDC(IntPtr hWnd,IntPtr hDc);
}

public class CaptureScreen
{
    public static Bitmap GetDesktopImage()
    {
        //In size variable we shall keep the size of the screen.
        SIZE size;

        //Variable to keep the handle to bitmap.
        IntPtr hBitmap;

        //Here we get the handle to the desktop device context.
        IntPtr  hDC = PlatformInvokeUSER32.GetDC(PlatformInvokeUSER32.GetDesktopWindow());

        //Here we make a compatible device context in memory for screen device context.
        IntPtr hMemDC = PlatformInvokeGDI32.CreateCompatibleDC(hDC);

        //We pass SM_CXSCREEN constant to GetSystemMetrics to get the
        //X coordinates of the screen.
        size.cx = PlatformInvokeUSER32.GetSystemMetrics(PlatformInvokeUSER32.SM_CXSCREEN);

        //We pass SM_CYSCREEN constant to GetSystemMetrics to get the Y coordinates of the screen.
        size.cy = PlatformInvokeUSER32.GetSystemMetrics (PlatformInvokeUSER32.SM_CYSCREEN);

        //We create a compatible bitmap of the screen size and using the screen device context.
        hBitmap = PlatformInvokeGDI32.CreateCompatibleBitmap(hDC, size.cx, size.cy);

        //As hBitmap is IntPtr, we cannot check it against null.
        //For this purpose, IntPtr.Zero is used.
        if(hBitmap != IntPtr.Zero)
        {
            //Here we select the compatible bitmap in the memeory device
            //context and keep the refrence to the old bitmap.
            IntPtr hOld = (IntPtr) PlatformInvokeGDI32.SelectObject(hMemDC, hBitmap);

            //We copy the Bitmap to the memory device context.
            PlatformInvokeGDI32.BitBlt(hMemDC, 0, 0, size.cx, size.cy, hDC, 0, 0, PlatformInvokeGDI32.SRCCOPY);

            //We select the old bitmap back to the memory device context.
            PlatformInvokeGDI32.SelectObject(hMemDC, hOld);

            //We delete the memory device context.
            PlatformInvokeGDI32.DeleteDC(hMemDC);

            //We release the screen device context.
            PlatformInvokeUSER32.ReleaseDC(PlatformInvokeUSER32.GetDesktopWindow(), hDC);

            //Image is created by Image bitmap handle and stored in local variable.
            Bitmap bmp = System.Drawing.Image.FromHbitmap(hBitmap);

            //Release the memory to avoid memory leaks.
            PlatformInvokeGDI32.DeleteObject(hBitmap);

            //This statement runs the garbage collector manually.
            GC.Collect();

            //Return the bitmap
            return bmp;
        }

        //If hBitmap is null, retun null.
        return null;
    }
}

//This structure shall be used to keep the size of the screen.
public struct SIZE
{
  public int cx;
  public int cy;
}