polygon offsetting: overlapping edges

[BigZebra101010]

Here is the sample code:

void DoMyShapes()
{
    Paths64 subjects;
    Paths64 solution;

    subjects.push_back(MakePath({ 9291660,1801720 , 9301100,1801720 , 9301100,1797900 , 9302420,1797900 , 9302420,1801720 , 9308260,1801720 , 9308260,1797900 , 9309580,1797900 , 9309580,1801720 , 9315420,1801720 , 9315420,1797900 , 9316740,1797900 , 9316740,1801720 , 9322580,1801720 , 9322580,1797900 , 9323900,1797900 , 9323900,1801720 , 9329740,1801720 , 9329740,1797900 , 9331060,1797900 , 9331060,1801720 , 9336900,1801720 , 9336900,1797900 , 9338220,1797900 , 9338220,1801720 , 9344060,1801720 , 9344060,1797900 , 9345380,1797900 , 9345380,1801720 , 9351220,1801720 , 9351220,1797900 , 9352540,1797900 , 9352540,1801720 , 9358380,1801720 , 9358380,1797900 , 9359700,1797900 , 9359700,1801720 , 9371940,1801720 , 9371940,1797900 , 9373260,1797900 , 9373260,1801720 , 9373260,1829560 , 9373260,1857400 , 9373260,1885240 , 9373260,1913220 , 9373260,1942860 , 9373260,1944180 , 9371940,1944180 , 9290340,1944180 , 9290340,1797900 , 9291660,1797900 }));
    subjects.push_back(MakePath({ 9291660,1885240 , 9301100,1885240 , 9301100,1880360 , 9302420,1880360 , 9302420,1885240 , 9308260,1885240 , 9308260,1880360 , 9309580,1880360 , 9309580,1885240 , 9315420,1885240 , 9315420,1880360 , 9316740,1880360 , 9316740,1885240 , 9322580,1885240 , 9322580,1880360 , 9323900,1880360 , 9323900,1885240 , 9329740,1885240 , 9329740,1880360 , 9331060,1880360 , 9331060,1885240 , 9336900,1885240 , 9336900,1880360 , 9338220,1880360 , 9338220,1885240 , 9344060,1885240 , 9344060,1880360 , 9345380,1880360 , 9345380,1885240 , 9351220,1885240 , 9351220,1880360 , 9352540,1880360 , 9352540,1885240 , 9358380,1885240 , 9358380,1880360 , 9359700,1880360 , 9359700,1885240 , 9371940,1885240 , 9371940,1895240 , 9359700,1895240 , 9359700,1899800 , 9358380,1899800 , 9358380,1895240 , 9352540,1895240 , 9352540,1899800 , 9351220,1899800 , 9351220,1895240 , 9345380,1895240 , 9345380,1899800 , 9344060,1899800 , 9344060,1895240 , 9338220,1895240 , 9338220,1899800 , 9336900,1899800 , 9336900,1895240 , 9331060,1895240 , 9331060,1899800 , 9329740,1899800 , 9329740,1895240 , 9323900,1895240 , 9323900,1899800 , 9322580,1899800 , 9322580,1895240 , 9316740,1895240 , 9316740,1899800 , 9315420,1899800 , 9315420,1895240 , 9309580,1895240 , 9309580,1899800 , 9308260,1899800 , 9308260,1895240 , 9302420,1895240 , 9302420,1899800 , 9301100,1899800 , 9301100,1895240 , 9291660,1895240 , 9291660,1913220 , 9301100,1913220 , 9301100,1908520 , 9302420,1908520 , 9302420,1913220 , 9308260,1913220 , 9308260,1908520 , 9309580,1908520 , 9309580,1913220 , 9315420,1913220 , 9315420,1908520 , 9316740,1908520 , 9316740,1913220 , 9322580,1913220 , 9322580,1908520 , 9323900,1908520 , 9323900,1913220 , 9329740,1913220 , 9329740,1908520 , 9331060,1908520 , 9331060,1913220 , 9336900,1913220 , 9336900,1908520 , 9338220,1908520 , 9338220,1913220 , 9344060,1913220 , 9344060,1908520 , 9345380,1908520 , 9345380,1913220 , 9351220,1913220 , 9351220,1908520 , 9352540,1908520 , 9352540,1913220 , 9358380,1913220 , 9358380,1908520 , 9359700,1908520 , 9359700,1913220 , 9371940,1913220 , 9371940,1923220 , 9359700,1923220 , 9359700,1927960 , 9358380,1927960 , 9358380,1923220 , 9352540,1923220 , 9352540,1927960 , 9351220,1927960 , 9351220,1923220 , 9345380,1923220 , 9345380,1927960 , 9344060,1927960 , 9344060,1923220 , 9338220,1923220 , 9338220,1927960 , 9336900,1927960 , 9336900,1923220 , 9331060,1923220 , 9331060,1927960 , 9329740,1927960 , 9329740,1923220 , 9323900,1923220 , 9323900,1927960 , 9322580,1927960 , 9322580,1923220 , 9316740,1923220 , 9316740,1927960 , 9315420,1927960 , 9315420,1923220 , 9309580,1923220 , 9309580,1927960 , 9308260,1927960 , 9308260,1923220 , 9302420,1923220 , 9302420,1927960 , 9301100,1927960 , 9301100,1923220 , 9291660,1923220 , 9291660,1942860 , 9371940,1942860 , 9371940,1923220 , 9371940,1885240 , 9371940,1867400 , 9359700,1867400 , 9359700,1872280 , 9358380,1872280 , 9358380,1867400 , 9352540,1867400 , 9352540,1872280 , 9351220,1872280 , 9351220,1867400 , 9345380,1867400 , 9345380,1872280 , 9344060,1872280 , 9344060,1867400 , 9338220,1867400 , 9338220,1872280 , 9336900,1872280 , 9336900,1867400 , 9331060,1867400 , 9331060,1872280 , 9329740,1872280 , 9329740,1867400 , 9323900,1867400 , 9323900,1872280 , 9322580,1872280 , 9322580,1867400 , 9316740,1867400 , 9316740,1872280 , 9315420,1872280 , 9315420,1867400 , 9309580,1867400 , 9309580,1872280 , 9308260,1872280 , 9308260,1867400 , 9302420,1867400 , 9302420,1872280 , 9301100,1872280 , 9301100,1867400 , 9291660,1867400 }));
    subjects.push_back(MakePath({ 9291660,1857400 , 9301100,1857400 , 9301100,1852840 , 9302420,1852840 , 9302420,1857400 , 9308260,1857400 , 9308260,1852840 , 9309580,1852840 , 9309580,1857400 , 9315420,1857400 , 9315420,1852840 , 9316740,1852840 , 9316740,1857400 , 9322580,1857400 , 9322580,1852840 , 9323900,1852840 , 9323900,1857400 , 9329740,1857400 , 9329740,1852840 , 9331060,1852840 , 9331060,1857400 , 9336900,1857400 , 9336900,1852840 , 9338220,1852840 , 9338220,1857400 , 9344060,1857400 , 9344060,1852840 , 9345380,1852840 , 9345380,1857400 , 9351220,1857400 , 9351220,1852840 , 9352540,1852840 , 9352540,1857400 , 9358380,1857400 , 9358380,1852840 , 9359700,1852840 , 9359700,1857400 , 9371940,1857400 , 9371940,1839560 , 9359700,1839560 , 9359700,1844120 , 9358380,1844120 , 9358380,1839560 , 9352540,1839560 , 9352540,1844120 , 9351220,1844120 , 9351220,1839560 , 9345380,1839560 , 9345380,1844120 , 9344060,1844120 , 9344060,1839560 , 9338220,1839560 , 9338220,1844120 , 9336900,1844120 , 9336900,1839560 , 9331060,1839560 , 9331060,1844120 , 9329740,1844120 , 9329740,1839560 , 9323900,1839560 , 9323900,1844120 , 9322580,1844120 , 9322580,1839560 , 9316740,1839560 , 9316740,1844120 , 9315420,1844120 , 9315420,1839560 , 9309580,1839560 , 9309580,1844120 , 9308260,1844120 , 9308260,1839560 , 9302420,1839560 , 9302420,1844120 , 9301100,1844120 , 9301100,1839560 , 9291660,1839560 }));
    subjects.push_back(MakePath({ 9291660,1829560 , 9301100,1829560 , 9301100,1824680 , 9302420,1824680 , 9302420,1829560 , 9308260,1829560 , 9308260,1824680 , 9309580,1824680 , 9309580,1829560 , 9315420,1829560 , 9315420,1824680 , 9316740,1824680 , 9316740,1829560 , 9322580,1829560 , 9322580,1824680 , 9323900,1824680 , 9323900,1829560 , 9329740,1829560 , 9329740,1824680 , 9331060,1824680 , 9331060,1829560 , 9336900,1829560 , 9336900,1824680 , 9338220,1824680 , 9338220,1829560 , 9344060,1829560 , 9344060,1824680 , 9345380,1824680 , 9345380,1829560 , 9351220,1829560 , 9351220,1824680 , 9352540,1824680 , 9352540,1829560 , 9358380,1829560 , 9358380,1824680 , 9359700,1824680 , 9359700,1829560 , 9371940,1829560 , 9371940,1811720 , 9359700,1811720 , 9359700,1816600 , 9358380,1816600 , 9358380,1811720 , 9352540,1811720 , 9352540,1816600 , 9351220,1816600 , 9351220,1811720 , 9345380,1811720 , 9345380,1816600 , 9344060,1816600 , 9344060,1811720 , 9338220,1811720 , 9338220,1816600 , 9336900,1816600 , 9336900,1811720 , 9331060,1811720 , 9331060,1816600 , 9329740,1816600 , 9329740,1811720 , 9323900,1811720 , 9323900,1816600 , 9322580,1816600 , 9322580,1811720 , 9316740,1811720 , 9316740,1816600 , 9315420,1816600 , 9315420,1811720 , 9309580,1811720 , 9309580,1816600 , 9308260,1816600 , 9308260,1811720 , 9302420,1811720 , 9302420,1816600 , 9301100,1816600 , 9301100,1811720 , 9291660,1811720 }));

    ClipperOffset co;
    co.AddPaths(subjects, JoinType::Miter, EndType::Polygon);
    co.Execute(-800, solution);

    FillRule fr = FillRule::NonZero;
    SvgWriter svg;
    svg.AddPaths(subjects, false, fr, 0x100066FF, 0x400066FF, 1, false);
    svg.AddPaths(solution, false, fr, 0x8066FF66, 0xFF006600, 1, false);
    svg.SaveToFile("size_by.svg", 800, 600, 0);
    System("size_by.svg");
}

the subject polygons:

the solution:

Should the results at 2 be the same as the results at 1?

[AngusJohnson]

Should the results at 2 be the same as the results at 1?

No. 😁

[BigZebra101010]

😂