.. default-role:: code

====================
Screenshot Functions
====================

PyAutoGUI can take screenshots, save them to files, and locate images within the screen. This is useful if you have a small image of, say, a button that needs to be clicked and want to locate it on the screen.

Screenshot functionality requires the Pillow module. OS X uses the `screencapture` command, which comes with the operating system. Linux uses the `scrot` command, which can be installed by running `sudo apt-get install scrot`.

Special Notes About Ubuntu
==========================

Unfortunately, Ubuntu seems to have several deficiencies with installing Pillow. PNG and JPEG support are not included with Pillow out of the box on Ubuntu. The following links have more information

The screenshot() Function
=========================

Calling `screenshot()` will return an Image object (see the Pillow or PIL module documentation for details). Passing a string of a filename will save the screenshot to a file as well as return it as an Image object.

.. code:: python

    >>> import pyautogui
    >>> im1 = pyautogui.screenshot()
    >>> im2 = pyautogui.screenshot('my_screenshot.png')

On a 1920 x 1080 screen, the `screenshot()` function takes roughly 100 milliseconds - it's not fast but it's not slow.


The Locate Functions
====================

You can visually locate something on the screen if you have an image file of it. For example, say the calculator app was running on your computer and looked like this:

.. image:: calculator.png

You can't call the `moveTo()` and `click()` functions if you don't know the exact screen coordinates of where the calculator buttons are. The calculator can appear in a slightly different place each time it is launched, causing you to re-find the coordinates each time. However, if you have an image of the button, such as the image of the 7 button:

.. image:: calc7key.png

. . . you can call the `locateOnScreen('calc7key.png')` function to get the screen coordinates. The return value is a 4-integer tuple: (left, top, width, height). This tuple can be passed to `center()` to get the X and Y coordinates at the center of this region. If the image can't be found on the screen, `locateOnScreen()` returns `None`.

    >>> import pyautogui
    >>> button7location = pyautogui.locateOnScreen('calc7key.png')
    >>> button7location
    (1416, 562, 50, 41)
    >>> button7x, button7y = pyautogui.center(button7location)
    >>> button7x, button7y
    (1441, 582)
    >>> pyautogui.click(button7x, button7y)  # clicks the center of where the 7 button was found

The `locateCenterOnScreen()` function is probably the one you want to use most often:

    >>> import pyautogui
    >>> x, y = pyautogui.locateCenterOnScreen('calc7key.png')
    >>> pyautogui.click(x, y)

On a 1920 x 1080 screen, the locate function calls take about 1 or 2 seconds. This may be too slow for action video games, but works for most purposes and applications.

There are several "locate" functions. They all start looking at the top-left corner of the screen (or image) and look to the left and then down. The arguments can either be a

- `locateOnScreen(image, grayscale=False)` - Returns (left, top, width, height) coordinate of first found instance of the `image` on the screen. Returns None if not found on the screen.

- `locateCenterOnScreen(image, grayscale=False)` - Returns (x, y) coordinates of the center of the first found instance of the `image` on the screen. Returns None if not found on the screen.

- `locateAllOnScreen(image, grayscale=False)` - Returns a generator that yields (left, top, width, height) tuples for where the image is found on the screen.

- `locate(needleImage, haystackImage, grayscale=False)` - Returns (left, top, width, height) coordinate of first found instance of `needleImage` in `haystackImage`. Returns None if not found on the screen.

- `locateAll(needleImage, haystackImage, grayscale=False)` - Returns a generator that yields (left, top, width, height) tuples for where `needleImage` is found in `haystackImage`.

The "locate all" functions can be used in for loops or passed to `list()`:

    >>> import pyautogui
    >>> for pos in pyautogui.locateAllOnScreen('someButton.png')
    ...   print(pos)
    ...
    (1101, 252, 50, 50)
    (59, 481, 50, 50)
    (1395, 640, 50, 50)
    (1838, 676, 50, 50)
    >>> list(pyautogui.locateAllOnScreen('someButton.png'))
    [(1101, 252, 50, 50), (59, 481, 50, 50), (1395, 640, 50, 50), (1838, 676, 50, 50)]

Grayscale Matching
------------------

Optionally, you can pass `grayscale=True` to the locate functions to give a slight speedup (about 30%-ish). This desaturates the color from the images and screenshots, speeding up the locating but potentially causing false-positive matches.

    >>> import pyautogui
    >>> button7location = pyautogui.locateOnScreen('calc7key.png', grayscale=True)
    >>> button7location
    (1416, 562, 50, 41)
