CODEWITHSUNDEEP
pythonopencvimage-processingpython-imaging-library
Stevphen
Stevphen

Reputation: 205

How do I crop a video steam that's already been resized?

I'm using PILs ImageGrab function to capture an application window in real-time for image detection with OpenCV. I've managed to scale the captured window down to increase the speed of image detection. However, I'm getting a number of false positives I can't seem to avoid. I actually only need to capture a small section of the window 761 34 1142 68

while True:
    # Grab PSS Window and find size 
    window = pygetwindow.getWindowsWithTitle('App')[0]
    x1 = window.left
    y1 = window.top
    height = window.height
    width = window.width
    x2 = x1 + width
    y2 = y1 + height
    # Actual Video Loop, cropped down to the specific window,
    # resized to 1/2 size, and converted to BGR for OpenCV
    haystack_img = ImageGrab.grab(bbox=(x1, y1, x2, y2))
    (width, height) = (haystack_img.width // 2, haystack_img.height // 2)
    haystack_img_resized = haystack_img.resize((width, height))
    
    ########### Line in Question ##############
    haystack_img_cropped = haystack_img_resized[761: 34, 1142:68]

    haystack_img_np = np.array(haystack_img_cropped) 
    haystack = cv.cvtColor(haystack_img_np, cv.COLOR_BGR2GRAY)
    cv.imshow("Screen", haystack)

I tried using OpenCV to slice the image but I get the error:

C:\Users\coyle\OneDrive\froggy-pirate-master\avoidShips>C:/Users/coyle/AppData/Local/Programs/Python/Python39/python.exe c:/Users/coyle/OneDrive/froggy-pirate-master/avoidShips/avoidShipActual/test7.py
Traceback (most recent call last):
  File "c:\Users\test7.py", line 103, in <module>
    objectDetection(ships_to_avoid, 0.92)
  File "c:\Users\test7.py", line 61, in objectDetection
    haystack_img_cropped = haystack_img_resized[761:34, 1142:68]
TypeError: 'Image' object is not subscriptable

And I tried the .crop method:

 haystack_img_resized = haystack_img.resize((width, height))
 haystack_img_resized.crop((761,34,1164,65))
 haystack_img_np = np.array(haystack_img_resized)

which produces no error but hasn't actually cropped anything.

How do I crop my video stream?

Upvotes: 0

Views: 84

Answers (2)

Stevphen
Stevphen

Reputation: 205

Not sure why, but loading the cropped image into a variable and using that variable worked.

crop = haystack_img_resized.crop((761,34,1164,65))
haystack_img_np = np.array(crop)

Upvotes: 1

saw
saw

Reputation: 378

haystack_img_cropped = np.array(haystack_img_resized)[761: 34, 1142:68] should work.

For your questions,

  1. You have to convert PIL's Image to Numpy's array before slicing.
  2. .crop() returns new modified PIL's Image instance rather than modifying the existing one. PIL's methods typically return a new Image instance.

Upvotes: 2

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