PolygonZone: estimate how much of the zone is occupied

[stevensagaert]

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Description

Next to the count of the objects in the zone, it would be useful to know how much of the zone area is occupied by the objects.

Use case

e.g. for loading zones in warehouses

Additional

Basically I've implemented it myself outside of the PolygonZone class. The core of what is needed is these two functions:

def polygon_to_binary_mask(img,contour):
    """convert bounding polygon coord to binary mask"""
    # Create binary mask
    b_mask = np.zeros(img.shape[:2], np.uint8)

    #  Extract contour result
    #contour = c.masks.xy.pop()
    #  Changing the type
    contour = contour.astype(np.int32) #Note: This must be int32 and not unit8!!!
    #  Reshaping
    contour = contour.reshape(-1, 1, 2)


    # Draw contour onto mask
    mask = cv2.drawContours(b_mask, [contour], -1, (1, 1, 1), cv2.FILLED)
    return mask

strategy:

1. make union of binary masks of detected objects (only the classes for consideration in zone)
2. make binary mask of the zone
3. do and of zone mask & object masks
4. sum the 1 pixels

def calculate_overlap_area(zone_mask, masks,show_plot=True):
    """calculate how much % of the zone is occupied"""
    #create one mask from the object masks as the union
    union_mask=np.bitwise_or.reduce(np.stack(masks),axis=0)
    #for debugging
    if show_plot:
        plt.title("union object mask")
        plt.imshow(union_mask,cmap='gray')
        plt.show()
    

    #do the bitwise and between union_mask & zone_mask
    overlap_mask=np.bitwise_and(union_mask,zone_mask)
    print(f"overlap_mask shape {overlap_mask.shape}")
    if show_plot:
        plt.title("overlap mask")
        plt.imshow(union_mask,cmap='gray')
        plt.show()
    
    overlap_size= np.sum(overlap_mask)
    zone_size=np.sum(zone_mask)
    return 100*overlap_size/zone_size

Are you willing to submit a PR?

• Yes I'd like to help by submitting a PR!