How can I save a screenshot directly to a file in Windows?

There is no way to save directly to a file without a 3rd party tool before Windows 8. Here are my personal favorite non-third party tool solutions.

For Windows 8 and later

+ PrintScreen saves the screenshot into a folder in <user>/Pictures/Screenshots

For Windows 7

In win 7 just use the snipping tool: Most easily accessed via pressing Start, then typing "sni" (enter). or then sni enter

Prior versions of Windows

I use the following keyboard combination to capture, then save using mspaint. After you do it a couple times, it only takes 2-3 seconds:

1. Alt+PrintScreen
2. Win+R ("run")
3. type "mspaint" enter
4. Ctrl-V (paste)
5. Ctrl-S (save)
6. use file dialog
7. Alt-F4 (close mspaint)

In addition, Cropper is great (and open source). It does rectangle capture to file or clipboard, and is of course free.

You can code something pretty simple that will hook the PrintScreen and save the capture in a file.

Here is something to start to capture and save to a file. You will just need to hook the key "Print screen".

using System;
using System.Drawing;
using System.IO;
using System.Drawing.Imaging;
using System.Runtime.InteropServices;
public class CaptureScreen
{

    static public void Main(string[] args)
    {

        try
        {
            Bitmap capture = CaptureScreen.GetDesktopImage();
            string file = Path.Combine(Environment.CurrentDirectory, "screen.gif");
            ImageFormat format = ImageFormat.Gif;
            capture.Save(file, format);
        }
        catch (Exception e)
        {
            Console.WriteLine(e);
        }

    }

    public static Bitmap GetDesktopImage()
    {
        WIN32_API.SIZE size;

        IntPtr  hDC = WIN32_API.GetDC(WIN32_API.GetDesktopWindow()); 
        IntPtr hMemDC = WIN32_API.CreateCompatibleDC(hDC);

        size.cx = WIN32_API.GetSystemMetrics(WIN32_API.SM_CXSCREEN);
        size.cy = WIN32_API.GetSystemMetrics(WIN32_API.SM_CYSCREEN);

        m_HBitmap = WIN32_API.CreateCompatibleBitmap(hDC, size.cx, size.cy);

        if (m_HBitmap!=IntPtr.Zero)
        {
            IntPtr hOld = (IntPtr) WIN32_API.SelectObject(hMemDC, m_HBitmap);
            WIN32_API.BitBlt(hMemDC, 0, 0,size.cx,size.cy, hDC, 0, 0, WIN32_API.SRCCOPY);
            WIN32_API.SelectObject(hMemDC, hOld);
            WIN32_API.DeleteDC(hMemDC);
            WIN32_API.ReleaseDC(WIN32_API.GetDesktopWindow(), hDC);
            return System.Drawing.Image.FromHbitmap(m_HBitmap); 
        }
        return null;
    }

    protected static IntPtr m_HBitmap;
}

public class WIN32_API
{
    public struct SIZE
    {
        public int cx;
        public int cy;
    }
    public  const int SRCCOPY = 13369376;
    public  const int SM_CXSCREEN=0;
    public  const int SM_CYSCREEN=1;

    [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);

    [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);
}

Update Here is the code to hook the PrintScreen (and other key) from C#:

Hook code

Little known fact: in most standard Windows (XP) dialogs, you can hit Ctrl+C to have a textual copy of the content of the dialog.
Example: open a file in Notepad, hit space, close the window, hit Ctrl+C on the Confirm Exit dialog, cancel, paste in Notepad the text of the dialog.
Unrelated to your direct question, but I though it would be nice to mention in this thread.

Beside, indeed, you need a third party software to do the screenshot, but you don't need to fire the big Photoshop for that. Something free and lightweight like IrfanWiew or XnView can do the job. I use MWSnap to copy arbitrary parts of the screen. I wrote a little AutoHotkey script calling GDI+ functions to do screenshots. Etc.

Might I suggest WinSnap http://www.ntwind.com/software/winsnap/download-free-version.html. It provides an autosave option and capture the alt+printscreen and other key combinations to capture screen, windows, dialog, etc.

You need a 3rd party screen grab utility for that functionality in XP. I dig Scott Hanselman's extensive blogging about cool tools and usually look there for such a utility -- sure enough, he's blogged about a couple here.

This will do it in Delphi. Note the use of the BitBlt function, which is a Windows API call, not something specific to Delphi.

Edit: Added example usage

function TForm1.GetScreenShot(OnlyActiveWindow: boolean) : TBitmap;
var
  w,h : integer;
  DC : HDC;
  hWin : Cardinal;
  r : TRect;
begin
  //take a screenshot and return it as a TBitmap.
  //if they specify "OnlyActiveWindow", then restrict the screenshot to the
  //currently focused window (same as alt-prtscrn)
  //Otherwise, get a normal screenshot (same as prtscrn)
  Result := TBitmap.Create;
  if OnlyActiveWindow then begin
    hWin := GetForegroundWindow;
    dc := GetWindowDC(hWin);
    GetWindowRect(hWin,r);
    w := r.Right - r.Left;
    h := r.Bottom - r.Top;
  end  //if active window only
  else begin
    hWin := GetDesktopWindow;
    dc := GetDC(hWin);
    w := GetDeviceCaps(DC,HORZRES);
    h := GetDeviceCaps(DC,VERTRES);
  end;  //else entire desktop

  try
    Result.Width := w;
    Result.Height := h;
    BitBlt(Result.Canvas.Handle,0,0,Result.Width,Result.Height,DC,0,0,SRCCOPY);
  finally
    ReleaseDC(hWin, DC) ;
  end;  //try-finally
end;

procedure TForm1.btnSaveScreenshotClick(Sender: TObject);
var
  bmp : TBitmap;
  savdlg : TSaveDialog;
begin
  //take a screenshot, prompt for where to save it
  savdlg := TSaveDialog.Create(Self);
  bmp := GetScreenshot(False);
  try
    if savdlg.Execute then begin
      bmp.SaveToFile(savdlg.FileName);
    end;
  finally
    FreeAndNil(bmp);
    FreeAndNil(savdlg);
  end;  //try-finally
end;

Try this: http://www.screenshot-utility.com/

From their homepage:

When you press a hotkey, it captures and saves a snapshot of your screen to a JPG, GIF or BMP file.

Without installing a screenshot autosave utility, yes you do. There are several utilities you can find however folr doing this.

For example: http://www.screenshot-utility.com/

Of course you could write a program that monitors the clipboard and displays an annoying SaveAs-dialog for every image in the clipboard ;-). I guess you can even find out if the last key pressed was PrintScreen to limit the number of false positives.

While I'm thinking about it.. you could also google for someone who already did exactly that.

EDIT: .. or just wait for someone to post the source here - as just happend :-)

Snagit...lots of tech folks use that.

As far as I know in XP, yes you must use some other app to actually save it.

Vista comes with the Snipping tool, that simplifies the process a bit!

You may want something like this: http://addons.mozilla.org/en-US/firefox/addon/5648

I think there is a version for IE and also with Explorer Integration. Pretty good software.