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ScreenGear API Usage Examples:⚓

After going through ScreenGear Usage Examples, Checkout more of its advanced configurations here ➶

Recommended: Install DXcam library on Windows Machines

On Windows Machines, if installed, ScreenGear API uses dxcam backend machines for higher FPS performance. Thereby, it is highly recommended to install it via pip as follows:

pip install dxcam

Bare-Minimum Usage⚓

Following is the bare-minimum code you need to get started with ScreenGear API:

# import required libraries
from vidgear.gears import ScreenGear
import cv2

# open video stream with default parameters
stream = ScreenGear().start()

# loop over
while True:

    # read frames from stream
    frame = stream.read()

    # check for frame if Nonetype
    if frame is None:
        break

    # {do something with the frame here}

    # Show output window
    cv2.imshow("Output Frame", frame)

    # check for 'q' key if pressed
    key = cv2.waitKey(1) & 0xFF
    if key == ord("q"):
        break

# close output window
cv2.destroyAllWindows()

# safely close video stream
stream.stop()

 

Using ScreenGear with Variable Screen Dimensions⚓

ScreenGear API provides us the flexibility to directly set the dimensions of capturing-area of the screen. These dimensions can be easily applied to ScreenGear API through its options dictionary parameter by formatting them as its attributes.

Supported Dimensional Attributes

ScreenGear API takes left, top, width, height coordinates of the bounding box of capture screen area(ROI), similar to PIL.ImageGrab.grab, defined below:

ScreenGear ROI region

  • left: the x-coordinate of the upper-left corner of the region
  • top: the y-coordinate of the upper-left corner of the region
  • width: the width of the complete region from left to the bottom-right corner of the region.
  • height: the height of the complete region from top to the bottom-right corner of the region.

The complete usage example is as follows:

# import required libraries
from vidgear.gears import ScreenGear
import cv2

# define dimensions of screen w.r.t to given monitor to be captured
options = {"top": 40, "left": 0, "width": 100, "height": 100}

# open video stream with defined parameters
stream = ScreenGear(logging=True, **options).start()

# loop over
while True:

    # read frames from stream
    frame = stream.read()

    # check for frame if Nonetype
    if frame is None:
        break

    # {do something with the frame here}

    # Show output window
    cv2.imshow("Output Frame", frame)

    # check for 'q' key if pressed
    key = cv2.waitKey(1) & 0xFF
    if key == ord("q"):
        break

# close output window
cv2.destroyAllWindows()

# safely close video stream
stream.stop()

 

Using ScreenGear with Multiple Screens⚓

ScreenGear API provides us the flexibility to select any connected display for fetching frames, with its monitor parameter:

Implication of using monitor parameter

Any value on monitor parameter other than None in ScreenGear API:

  • Will enforce dxcam library backend on Windows platform (if installed), and mss library backend otherwise.
  • Will discard any value on its backend parameter.
Using GPU acceleration on Windows

With dxcam library backend, you can also assign which GPU devices ids to use along with monitor device ids as tuple (monitor_idx, gpu_idx), as follows:

# open video stream with defined parameters with 
# monitor at index `1` and GPU at index `0`.
stream = ScreenGear(monitor=(1,0), logging=True).start()

Getting a complete list of monitor devices and GPUs

To get a complete list of monitor devices and outputs(GPUs), you can use dxcam library itself:

>>> import dxcam
>>> dxcam.device_info()
'Device[0]:<Device Name:NVIDIA GeForce RTX 3090 Dedicated VRAM:24348Mb VendorId:4318>\n'
>>> dxcam.output_info()
'Device[0] Output[0]: Res:(1920, 1080) Rot:0 Primary:True\nDevice[0] Output[1]: Res:(1920, 1080) Rot:0 Primary:False\n'

# import required libraries
from vidgear.gears import ScreenGear
import cv2

# open video stream with defined parameters with monitor at index `1` selected
stream = ScreenGear(monitor=1, logging=True).start()

# loop over
while True:

    # read frames from stream
    frame = stream.read()

    # check for frame if Nonetype
    if frame is None:
        break

    # {do something with the frame here}

    # Show output window
    cv2.imshow("Output Frame", frame)

    # check for 'q' key if pressed
    key = cv2.waitKey(1) & 0xFF
    if key == ord("q"):
        break

# close output window
cv2.destroyAllWindows()

# safely close video stream
stream.stop()

With mss library backend, You can also assign monitor value to -1 to fetch frames from all connected multiple monitor screens with mss backend.

With mss library backend, API will output BGRA colorspace frames instead of default BGR.

# import required libraries
from vidgear.gears import ScreenGear
import cv2

# open video stream with defined parameters with monitor at index `1` selected
stream = ScreenGear(monitor=1, logging=True).start()

# loop over
while True:

    # read frames from stream
    frame = stream.read()

    # check for frame if Nonetype
    if frame is None:
        break

    # {do something with the frame here}

    # Show output window
    cv2.imshow("Output Frame", frame)

    # check for 'q' key if pressed
    key = cv2.waitKey(1) & 0xFF
    if key == ord("q"):
        break

# close output window
cv2.destroyAllWindows()

# safely close video stream
stream.stop()

 

Using ScreenGear with Variable Backend⚓

With ScreenGear API, you can select from many different backends that generates best performance as well as the most compatible with our machine by employing its backend parameter that supports many different backends:

Supported backend values

Its possible values are: dxcam (Windows only), pil, mss, scrot, maim, imagemagick, pyqt5, pyqt, pyside2, pyside, wx, pygdk3, mac_screencapture, mac_quartz, gnome_dbus, gnome-screenshot, kwin_dbus.

Remember to install backend library and all of its dependencies you're planning to use with ScreenGear API. More information on all these backends (except dxcam) can be found here ➶

Backend defaults to dxcam library on Windows (if installed), and pyscreenshot otherwise.

Any value on monitor parameter will disable the backend parameter. You cannot use them simultaneously.

# import required libraries
from vidgear.gears import ScreenGear
import cv2

# open video stream with defined parameters and `mss` backend 
# for extracting frames.
stream = ScreenGear(backend="mss", logging=True).start()

# loop over
while True:

    # read frames from stream
    frame = stream.read()

    # check for frame if Nonetype
    if frame is None:
        break

    # {do something with the frame here}

    # Show output window
    cv2.imshow("Output Frame", frame)

    # check for 'q' key if pressed
    key = cv2.waitKey(1) & 0xFF
    if key == ord("q"):
        break

# close output window
cv2.destroyAllWindows()

# safely close video stream
stream.stop()

 

Using ScreenGear with Direct Colorspace Manipulation⚓

ScreenGear API also supports Direct Colorspace Manipulation, which is ideal for changing source colorspace on the run.

A more detailed information on colorspace manipulation can be found here ➶

In following example code, we will start with HSV as source colorspace, and then we will switch to GRAY colorspace when w key is pressed, and then LAB colorspace when e key is pressed, finally default colorspace (i.e. BGR) when s key is pressed. Also, quit when q key is pressed:

Any incorrect or None-type value, will immediately revert the colorspace to default i.e. BGR.

# import required libraries
from vidgear.gears import ScreenGear
import cv2

# Change colorspace to `HSV`
stream = ScreenGear(colorspace="COLOR_BGR2HSV", logging=True).start()

# loop over
while True:

    # read HSV frames
    frame = stream.read()

    # check for frame if Nonetype
    if frame is None:
        break

    # {do something with the HSV frame here}

    # Show output window
    cv2.imshow("Output Frame", frame)

    # check for key if pressed
    key = cv2.waitKey(1) & 0xFF

    # check if 'w' key is pressed
    if key == ord("w"):
        # directly change colorspace at any instant
        stream.color_space = cv2.COLOR_BGR2GRAY  # Now colorspace is GRAY

    # check for 'e' key is pressed
    if key == ord("e"):
        stream.color_space = cv2.COLOR_BGR2LAB  # Now colorspace is CieLAB

    # check for 's' key is pressed
    if key == ord("s"):
        stream.color_space = None  # Now colorspace is default(ie BGR)

    # check for 'q' key is pressed
    if key == ord("q"):
        break

# close output window
cv2.destroyAllWindows()

# safely close video stream
stream.stop()

 

Using ScreenGear with WriteGear API⚓

ScreenGear can be used in conjunction with WriteGear API directly without any compatibility issues. The suitable example is as follows:

# import required libraries
from vidgear.gears import ScreenGear
from vidgear.gears import WriteGear
import cv2


# define dimensions of screen w.r.t to given monitor to be captured
options = {"top": 40, "left": 0, "width": 100, "height": 100}

# define suitable (Codec,CRF,preset) FFmpeg parameters for writer
output_params = {"-vcodec": "libx264", "-crf": 0, "-preset": "fast"}

# open video stream with defined parameters
stream = ScreenGear(monitor=1, logging=True, **options).start()

# Define writer with defined parameters and suitable output filename for e.g. `Output.mp4`
writer = WriteGear(output="Output.mp4", logging=True, **output_params)

# loop over
while True:

    # read frames from stream
    frame = stream.read()

    # check for frame if Nonetype
    if frame is None:
        break

    # {do something with the frame here}
    # lets convert frame to gray for this example
    gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)

    # write gray frame to writer
    writer.write(gray)

    # Show output window
    cv2.imshow("Output Gray Frame", gray)

    # check for 'q' key if pressed
    key = cv2.waitKey(1) & 0xFF
    if key == ord("q"):
        break

# close output window
cv2.destroyAllWindows()

# safely close video stream
stream.stop()

# safely close writer
writer.close()

 


Last update: September 2, 2023