For a subject I am interested in as a hobby, I need to determine the corner coordinates of the display you see in the photo. I do not have theoretical knowledge about Python and computer vision, but I am trying to do it with the help of examples on the internet.

At my last point, it seems that I can detect the display on the computer, but I could not find the corner coordinates of the largest detected rectangle. The x,y,w,h values ​​it gives me are very irrelevant.

Can you help me understand what the mistake is in the code I shared? Thanks in advance

`## get contour function
def getContours(img, imgContour):
contours, hierarchy = cv2.findContours(img, cv2.RETR_EXTERNAL, cv2.CHAIN_APPROX_SIMPLE)
cv2.drawContours(imgContour, contours, -1, (255, 0, 255), 7)

maxArea = 0
maxContour = None

for cnt in contours:
    area = cv2.contourArea(cnt)
    print(f"Contour area: {area}")
    if area > maxArea:
        maxArea = area
        maxContour = cnt

if maxContour is not None:
    peri = cv2.arcLength(maxContour, True)
    approx = cv2.approxPolyDP(maxContour, 0.02 * peri, True)
    print(f"Number of approx vertices: {len(approx)}")
    if len(approx) == 4 and maxArea > 100000:  # Dikdörtgen olma ve alan kontrolü
        x, y, w, h = cv2.boundingRect(approx)
        cv2.drawContours(imgContour, [approx], -1, (0, 255, 0), 5)
        return x, y, w, h
return None`

`## Infinite While loop

imgContour = img.copy()
imgBlur = cv2.GaussianBlur(img, (7, 7), 1)
imgGray = cv2.cvtColor(imgBlur, cv2.COLOR_BGR2GRAY)
threshold1 = cv2.getTrackbarPos("Threshold1", "Parameters")
threshold2 = cv2.getTrackbarPos("Threshold2", "Parameters")
imgCanny = cv2.Canny(imgGray, threshold1, threshold2)
kernel = np.ones((7, 7))
imgDil = cv2.dilate(imgCanny, kernel, iterations=1)
rect = getContours(imgDil, imgContour)
if rect:
    x, y, w, h = rect  # Boyut filtresi
    print(f"Largest rectangle: x={x}, y={y}, w={w}, h={h}")
    cv2.rectangle(imgContour, (x, y), (x + w, y + h), (0, 255, 0), 2)
    cv2.putText(imgContour, f"x={x}, y={y}, w={w}, h={h}", (x, y - 10), cv2.FONT_HERSHEY_SIMPLEX, 0.6, (0, 255, 0), 2)
else:
    print("No rectangle found.")

`

(https://i.sstatic.net/3wpHcYlD.png)

I expect to get pixel values ​​like (452,365), (1049,452), but the values ​​I get are around x = 70, y = 70, w = 200, h = 103.