Halcon loops to find the pads on multiple circuit boards (the effective area of the PCB board is not the same in the figure)

1 Description of the problem

As shown in the figure, find the pads on the following four circuit boards in a loop; the
effective areas of the four pictures have different positions in the pictures;
and there are rectangular black blocks similar to the pad area in the picture;

In order to improve efficiency, first find the product (circuit board);
then find the small black block, and then subtract the small rectangular block from it;