How To Detect There Is A Piece On A Chess Board

Question

I'm Tring To Convert A Chess Board Image Into A Matrix With The Pieces On The Board.

like so:

[
 [P, P, P, P, P, P, P, P,]
 [P, P, P, P, P, P, P, P,]
 [-, -, -, -, -, -, -, -,]
 [-, -, -, -, -, -, -, -,]
 [P, P, P, P, P, P, P, P,]
 [P, P, P, P, P, P, P, P,]
]

I Used Threshold To Get Pieces But The Is The Best Indicator That The Square Has A Piece In It.

Script

img_gray = cv2.cvtColor(img, cv2.COLOR_RGB2GRAY)

BOARD = 430
DIMENSION = 8 # dimensions of chess is 8*8
SQ_size = BOARD // DIMENSION
START_X = 40
START_Y = 33
DARK_SQUARE_THRESHOLD = 150
for row in range(8):
for col in range(8):

    piece_image = img_gray[y:y + SQ_size, x: x + SQ_size]
    th3 = cv2.adaptiveThreshold(piece_image,255, cv2.ADAPTIVE_THRESH_GAUSSIAN_C,\ 
    cv2.THRESH_BINARY,11,2)
         image = cv2.rectangle(img, (x, y), (x + SQ_size, y + SQ_size), (0, 0, 0), 2)
    x += SQ_size

x = START_X
y += SQ_size

This Is The Result Image: