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using test_t = bitmap<alpha_pixel<1>>;
uint8_t test_data[test_t::sizeof_buffer(faAnchorCircleCheck_size)];
void gen_1bit() {
    size_t i = 0;
    size_t idx = 0;
    size_t offs = 0;
    uint8_t tmp = 0;
    for(int y = 0;y<faAnchorLock.dimensions().height;++y) {
        for(int x = 0;x<faAnchorLock.dimensions().width;++x) {
            decltype(faAnchorLock)::pixel_type px;
            faAnchorLock.point(point16(x,y),&px);
            float luma =px.template channelr<0>();
            if((luma>=.5)) {
                tmp|=(1<<(7-offs));
            }
            ++i;
            ++offs;
            if(8==offs) {
                test_data[idx]=tmp;
                tmp=0;
                offs=0;
                ++idx;
            }
        }
    }
    if(offs!=0) {
        test_data[idx]=tmp;
    }
}