Untitled

from matplotlib.path import Path
from matplotlib.patches import PathPatch

def interpolate_points(ax, x, y, pad, open=True, absolute_pad=False, **kwargs):
  codes = []
  verts = []
  if open:
    # First point
    code = Path.MOVETO
    vert = (x[0], y[0])
    codes.append(code)
    verts.append(vert)
    # Interpolate points between
    for i in range(1, len(x)-1):
      # LINETO (from previous to this point)
      code = Path.LINETO
      dx = (x[i] - x[i-1]) * (1 - pad)
      dy = (y[i] - y[i-1]) * (1 - pad)
      xij = x[i-1] + dx
      yij = y[i-1] + dy
      vert = (xij, yij)
      codes.append(code)
      verts.append(vert)
      # CURVETO
      code = Path.CURVE3
      xij = x[i]
      yij = y[i]
      vert = (xij, yij)
      codes.append(code)
      verts.append(vert)
      # CURVETO
      code = Path.CURVE3
      xij = x[i] + (x[i+1] - x[i]) * pad
      yij = y[i] + (y[i+1] - y[i]) * pad
      vert = (xij, yij)
      codes.append(code)
      verts.append(vert)
    # Last point
    code = Path.LINETO
    vert = (x[-1], y[-1])
    codes.append(code)
    verts.append(vert) 
  else:
    # First point
    code = Path.MOVETO
    xij = x[0] + (x[1] - x[0]) * pad
    yij = y[0] + (y[1] - y[0]) * pad
    vert = (xij, yij)
    codes.append(code)
    verts.append(vert)
    # Interpolate points between
    for i in range(1, len(x)-1):
      # LINETO
      code = Path.LINETO
      xij = x[i-1] + (x[i] - x[i-1]) * (1 - pad)
      yij = y[i-1] + (y[i] - y[i-1]) * (1 - pad)
      vert = (xij, yij)
      codes.append(code)
      verts.append(vert)
      # CURVETO
      code = Path.CURVE3
      xij = x[i]
      yij = y[i]
      vert = (xij, yij)
      codes.append(code)
      verts.append(vert)
      # CURVETO
      code = Path.CURVE3
      xij = x[i] + (x[i+1] - x[i]) * pad
      yij = y[i] + (y[i+1] - y[i]) * pad
      vert = (xij, yij)
      codes.append(code)
      verts.append(vert)
    # Last point
    code = Path.LINETO
    xij = x[-2] + (x[-1] - x[-2]) * (1 - pad)
    yij = y[-2] + (y[-1] - y[-2]) * (1 - pad)
    vert = (xij, yij)
    codes.append(code)
    verts.append(vert)
    # CURVETO
    code = Path.CURVE3
    xij = x[-1]
    yij = y[-1]
    vert = (xij, yij)
    codes.append(code)
    verts.append(vert)
    # CURVETO
    code = Path.CURVE3
    xij = x[-1] + (x[0] - x[-1]) * pad
    yij = y[-1] + (y[0] - y[-1]) * pad
    vert = (xij, yij)
    codes.append(code)
    verts.append(vert)
    # Back to first point
    code = Path.LINETO
    xij = x[-1] + (x[0] - x[-1]) * (1 - pad)
    yij = y[-1] + (y[0] - y[-1]) * (1 - pad)
    vert = (xij, yij)
    codes.append(code)
    verts.append(vert)
    # CURVETO
    code = Path.CURVE3
    xij = x[0]
    yij = y[0]
    vert = (xij, yij)
    codes.append(code)
    verts.append(vert)
    # CURVETO
    code = Path.CURVE3
    xij = x[0] + (x[1] - x[0]) * pad
    yij = y[0] + (y[1] - y[0]) * pad
    vert = (xij, yij)
    codes.append(code)
    verts.append(vert)

  rounded_verts = Path(verts, codes)
  rounded_verts = PathPatch(rounded_verts, **kwargs)
  ax.add_patch(rounded_verts)

fig = matplotlib.pyplot.figure(dpi=220)
box = fig.hbox(1)
ax = box.children[0]

x = np.array([0.25, 0.25, 0.75, 0.75])
y = np.array([0, 1, 1, 0])

interpolate_points(ax, x, y, 0.2, open=False, facecolor=dv.colors['green'][2], edgecolor=dv.green)