/ 
Imager-Screenshot-0.014
River stage one • 2 direct dependents • 3 total dependents
/ Imager::Screenshot

NAME

Imager::Screenshot - screenshot to an Imager image

SYNOPSIS

use Imager::Screenshot 'screenshot';

# whole screen
my $img = screenshot();

# Win32 window
my $img2 = screenshot(hwnd => $hwnd);

# X11 window
my $img3 = screenshot(display => $display, id => $window_id);

# X11 tools
my $display = Imager::Screenshot::x11_open();
Imager::Screenshot::x11_close($display);

# test for win32 support
if (Imager::Screenshot->have_win32) { ... }

# test for x11 support
if (Imager::Screenshot->have_x11) { ... }

# test for Darwin (Mac OS X) support
if (Imager::Screenshot->have_darwin) { ... }

DESCRIPTION

Imager::Screenshot captures either a desktop or a specified window and returns the result as an Imager image.

Currently the image is always returned as a 24-bit image.

screenshot hwnd => window handle
screenshot hwnd => window handle, decor => <capture decorations>
screenshot hwnd => "active"

Retrieve a screenshot under Win32, if window handle is zero, capture the desktop.

By default, window decorations are not captured, if the decor parameter is set to true then window decorations are included.

As of 0.010 hwnd can also be "active" to capture the active (or "foreground") window.

screenshot hwnd => 0

Retrieve a screeshot of the default desktop under Win32.

screenshot hwnd => 0, monitor => -1

Retrieve a screenshot of all attached monitors under Win32.

Note: this returns an image with an alpha channel, since there can be regions in the bounding rectangle of all monitors that no particular monitor covers.

screenshot hwnd => 0, monitor => index

Retrieve a screenshot from a particular monitor under Win32. A monitor of zero is always treated as the primary monitor.

If the given monitor is not active screenshot() will fail.

screenshot id => window id
screenshot id => window id, display => display object

Retrieve a screenshot under X11, if id is zero, capture the root window. display object is a integer version of an X11 Display * , if this isn't supplied screenshot() will attempt connect to the the display specified by $ENV{DISPLAY}.

By default this works by always capturing from the root window, adjusting for the position of the supplied window if one is supplied.

To capture directly from the window, which returns a completely black image on some platforms, supply a direct => 1 parameter.

Note: taking a screenshot of a remote display is slow.

screenshot darwin => 0

Retrieve a screenshot under Mac OS X. The only supported value for the darwin parameter is 0.

For a screen capture to be taken, the current user using Imager:Screenshot must be the currently logged in user on the display.

If you're using fast user switching, the current user must be the active user.

Note: this means you can ssh into a Mac OS X box and screenshot from the ssh session, if you're the current user on the display.

screenshot widget => widget
screenshot widget => widget, display => display
screenshot widget => widget, decor => capture decorations

Retrieve a screenshot of a Tk widget, under Win32 or X11, depending on how Tk has been built.

If Tk was built for X11 then the display parameter applies.

If Tk was built for Win32 then the decor parameter applies.

screenshot

If no id, hwnd or widget parameter is supplied:

  • if Win32 support is compiled, return screenshot(hwnd => 0).

  • if Darwin support is compiled, return screenshot(darwin => 0).

  • if X11 support is compiled, return screenshot(id => 0).

  • otherwise, die.

You can also supply the following parameters to retrieve a subset of the window:

  • left

  • top

  • right

  • bottom

If left or top is negative, then treat that as from the right/bottom edge of the window.

If right ot bottom is zero or negative then treat as from the right/bottom edge of the window.

So setting all 4 values to 0 retrieves the whole window.

# a 10-pixel wide right edge of the window
my $right_10 = screenshot(left => -10, ...);

# the top-left 100x100 portion of the window
my $topleft_100 = screenshot(right => 100, bottom => 100, ...);

# 10x10 pixel at the bottom right corner
my $bott_right_10 = screenshot(left => -10, top => -10, ...);

If screenshot() fails, it will return nothing, and the cause of the failure can be retrieved via Imager->errstr, so typical use could be:

my $img = screenshot(...) or die Imager->errstr;
have_win32

Returns true if Win32 support is available.

have_x11

Returns true if X11 support is available.

have_darwin

Returns true if Darwin support is available.

Imager::Screenshot::x11_open
Imager::Screenshot::x11_open display name

Attempts to open a connection to either the display name in $ENV{DISPLAY} or the supplied display name. Returns a value suitable for the display parameter of screenshot, or undef.

Imager::Screenshot::x11_close display

Closes a display returned by Imager::Screenshot::x11_open().

TAGS

screenshot() sets a number of tags in the images it returns, these are:

  • ss_left - the distance between the left side of the window and the left side of the captured area. The same value as the left parameter when that is positive.

  • ss_top - the distance between the top side of the window the top side of the captured area. The same value at the top parameter when that is positive.

  • ss_window_width - the full width of the window.

  • ss_window_height - the full height of the window.

  • ss_type - the type of capture done, either "Win32" or "X11".

To cheaply get the window size you can capture a single pixel:

my $im = screenshot(right => 1, bottom => 1);
my $window_width  = $im->tags(name => 'ss_window_width');
my $window_height = $im->tags(name => 'ss_window_height');

CAVEATS

It's possible to have more than one grab driver available, for example, Win32 and X11, and which is used can have an effect on the result.

Under Win32 or OS X, if there's a screesaver running, then you grab the results of the screensaver.

On OS X, you can grab the display from an ssh session as long as the ssh session is under the same user as the currently active user on the display.

Grabbing the root window on a rootless server (eg. Cygwin/X) may not grab the background that you see. In fact, when I tested under Cygwin/X I got the xterm window contents even when the Windows screensaver was running. The root window captured appeared to be that generated by my window manager.

Grabbing a window with other windows overlaying it will capture the content of those windows where they hide the window you want to capture. You may want to raise the window to top. This may be a security concern if the overlapping windows contain any sensitive information - true for any screen capture.

LICENSE

Imager::Screenshot is licensed under the same terms as Perl itself.

TODO

Future plans include:

  • window name searches - currently screenshot() requires a window identifier of some sort, it would be more usable if we could supply some other identifier, either a window title or a window class name.

AUTHOR

Tony Cook <tonyc@cpan.org>