.\modules\objdetect\src\erfilter.cpp 260

<pre>
unsigned char quads[3][4];
quads[0][0] = 1 << 3;
quads[0][1] = 1 << 2;
quads[0][2] = 1 << 1;
quads[0][3] = 1;
quads[1][0] = (1<<2)|(1<<1)|(1);
quads[1][1] = (1<<3)|(1<<1)|(1);
quads[1][2] = (1<<3)|(1<<2)|(1);
quads[1][3] = (1<<3)|(1<<2)|(1<<1);
quads[2][0] = (1<<2)|(1<<1);
quads[2][1] = (1<<3)|(1);
quads[2][3] = 255; // <=== quads[2][2] lack
</pre>