Incorrect interaction area calculation

[kangskii]

Hi,
In yout iou() function, you cannot calculate the interaction AREA by the following equation:
(Line16) intersection = x * y

In my opinion, we cannot calculate the overlap if we only know the width and heights of the two boxes.
Please help to double check and iou() function.

[lars76]

Hi, let's look at the original IoU formula in the numerator (intersection): (min(x_A2, x_B2) - max(x_A1, x_B1))(min(y_A2, y_B2) - max(y_A1, y_B1)). Now we shift all boxes to the origin. Then (min(x_A2', x_B2') - max(0, 0))(min(y_A2', y_B2') - max(0, 0)) = min(x_A2', x_B2') * min(y_A2', y_B2'), which is line 16.

So we are actually considering both coordinates, but the lower point of each box is (0, 0) and the upper point is (x2, y2). I hope this makes sense.

[kangskii]

Now it is clear for me. Thanks for your answer.