有人知道——在Matplotlib中——如何用半透明的颜色生成好看的填充等高线图吗？如果向contourf()传递半透明颜色的颜色贴图，则填充区域之间会产生小间隙：
根据docs，这不是一个bug(“contourf()[…]不绘制多边形边”)。要绘制边缘，建议“添加调用contour()的线条轮廓”。但这看起来也不好，因为边缘变得太不透明：
您可以使用linewidth的linewidth参数，但这没有多大帮助。有什么想法吗？在
下面是重现问题的代码(我使用面向对象的API，但结果与pyplot相同)：import matplotlib
import numpy as np
from matplotlib.figure import Figure
from matplotlib.backends.backend_agg import FigureCanvasAgg
# generate some data
shape = (100, 100)
x_rng = np.linspace(-1, 1, shape[1])
y_rng = np.linspace(-1, 1, shape[0])
x, y = np.meshgrid(x_rng, y_rng)
z = np.sqrt(x**2 + y**2)
# create figure
width_inch, height_inch = 5, 5 # results in 500x500px with dpi=100
fig = Figure()
fig.set_size_inches((width_inch, height_inch))
FigureCanvasAgg(fig)
ax = fig.add_axes([0., 0., 1., 1.])
ax.set_axis_off()
# define some colors with alpha < 1
alpha = 0.9
colors = [
(0.1, 0.1, 0.5, alpha), # dark blue
(0.0, 0.7, 0.3, alpha), # green
(0.9, 0.2, 0.7, alpha), # pink
(0.0, 0.0, 0.0, alpha), # black
(0.1, 0.7, 0.7, alpha), # light blue
]
cmap = matplotlib.colors.ListedColormap(colors)
levels = np.array(np.linspace(0, z.max(), len(colors)))
norm = matplotlib.colors.BoundaryNorm(levels, ncolors=cmap.N)
# contourf plot produces small gaps between filled areas
cnt = ax.contourf(x, y, z, levels, cmap=cmap, norm=norm,
antialiased=True, linecolor='none')
# this fills the gaps, but it makes them too opaque
# ax.contour(x, y, z, levels, cmap=cmap, norm=norm,
# antialiased=True)
# the same is true for this trick:
# for c in cnt.collections:
# c.set_edgecolor("face")
filename = "/tmp/contourf.png"
fig.savefig(filename, dpi=100, transparent=True, format="png")
PS：SVG后端同样的图看起来不错。在
PPS:pcolormesh()也有类似的问题：
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