Simulating print Screen functions

Simulating print Screen functions

Phoenix_256

Member #8,316

February 2007

Heya,

I want to write a program that startup takes a screenshot of what ever is on the screen to use as a background within the program.

I've already found the fantastic code to get a bitmap from the clipboard, so I thought that using 'simulate_key(KEY_PRTSCR);' would copy it to the clipboard, but Windows doesn't accept the key press (it ignores it) I guess that simulate_key simply sets that keys flag to true, but what I'd like to find out is; is there another way to capture the screen image?

I've included the code below.

Cheers

Phoenix

1#include <allegro.h>
2#include <winalleg.h>
3 
4BITMAP* getBitmapFromClipboard() {
  BITMAP *result = NULL;
  
  if (!IsClipboardFormatAvailable(CF_BITMAP)) {
      return NULL;
  }
  
  if (OpenClipboard(win_get_window())) {
      HBITMAP hbmp;
      
      hbmp = GetClipboardData(CF_BITMAP);
      if (hbmp != NULL) {
          result = convert_hbitmap_to_bitmap(hbmp);
      } 
      CloseClipboard();
  } 
  return result;
21}
22 
23 
24 
25int main(int argc, char** argv) {
  BITMAP *bmp;
  
  allegro_init();
  install_timer();
  install_mouse();
  install_keyboard();
  simulate_keypress(KEY_PRTSCR);
  rest(1000);
  set_color_depth(32);
  set_gfx_mode(1,1024,768, 0, 0);
  
  bmp = getBitmapFromClipboard();
  
  if (bmp) {
          // Draw a rectangle on it just to test!!
          rectfill(bmp,100,100,200,200,makecol(255,0,255));
          blit(bmp, screen, 0, 0, 0, 0, bmp->w, bmp->h);
  }
  clear_keybuf();
  readkey();
46 
  destroy_bitmap(bmp);
48 
  allegro_exit();
50}
51END_OF_MAIN()

Andrei Ellman

Member #3,434

April 2003

Allegro does not provide a way to grab an image of the desktop. Each operating system has a different means of accessing the desktop image. For Windows, you might want to look at the sourcecode for ChromaPlas to see how it's done on Windows.

AE.

--
Don't let the illegitimates turn you into carbon.

Jakub Wasilewski

Member #3,653

June 2003

Basically, you would use GetDC(NULL) to get a HDC for the entire screen.

Then, you can use Windows specific Allegro functions, described here in the manual. Specifically, you want blit_from_hdc.

If you want to use that, be sure to include winalleg.h.

---------------------------
[ ChristmasHack! | My games ] :::: One CSS to style them all, One Javascript to script them, / One HTML to bring them all and in the browser bind them / In the Land of Fantasy where Standards mean something.

ImLeftFooted

Member #3,935

October 2003

Grabbing a picture of the desktop is no longer possible for screen savers as of XP.

How is my posting?

BAF

Member #2,981

December 2002

But you can grab a screenshot in a screen saver, right?

BAF.zone | SantaHack!

Andrei Ellman

Member #3,434

April 2003

Dustin Dettmer said:

Grabbing a picture of the desktop is no longer possible for screen savers as of XP.

Is that only as of XP SP2? I could have sworn I've gotten ChromaPlas in desptop-image mode to work on an XP-based machine.

Even if it were true, it would be a pity, as it would prevent the many screensavers that maipulate the desktop image from working.

AE.

--
Don't let the illegitimates turn you into carbon.