有人知道 - 在Matplotlib中 - 如何用半透明色生成一個漂亮的填充輪廓圖?如果contourf()
傳遞用半透明顏色的顏色表,它產生小的間隙的填充區域之間:Matplotlib:用透明色填充等值線圖
按照docs,這不是錯誤(」 contourf()
[...]不繪製多邊形邊「)。爲了繪製邊緣,建議「通過調用contour()
添加線輪廓」。但是,這並不好看無論是作爲邊緣變得太不透明:
你可以玩弄的contour()
的linewidth
說法,但不會有什麼幫助。有任何想法嗎?
下面是重現該問題的代碼(我用的是面向對象的API,但結果是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:同樣的情節看起來不錯,與SVG後端。
PPS:pcolormesh()
有類似的問題:
ax.pcolormesh(x, y, z, cmap=cmap, norm=norm,
edgecolor="face", antialiased=True)
備註:''antialiased = True''似乎有效果(但關閉它也不會產生好的結果)。 – weatherfrog