SetLineWidth ， How to change only the height of the line instead of its width

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SetLineWidth is proportionally scaled,

How to change only the height of the line instead of its width

For example, the image at the bottom

func TestAA(t *testing.T) {

	dc := gg.NewContext(1000, 1000)
	dc.SetRGB(1, 1, 1)
	dc.Clear()
	dc.SetRGB(0, 0, 0)
	w := 0.1
	for i := 100; i <= 900; i += 20 {
		x := float64(i)
		dc.DrawLine(x+50, 0, x-50, 1000)
		dc.SetLineWidth(w)

		dc.SetDash(2, 8, 8, 16)

		dc.Stroke()
		w += 0.2
	}
	dc.SavePNG("out11.png")
}