如何在matplotlib python中动态更改alpha值
我正在寻找如何动态更改已绘制的alpha值 这是我想要实现的一种示例代码,但我知道这是一种错误的编写方法如何在matplotlib python中动态更改alpha值,python,matplotlib,Python,Matplotlib,我正在寻找如何动态更改已绘制的alpha值 这是我想要实现的一种示例代码,但我知道这是一种错误的编写方法 import matplotlib.pyplot as plt fig = plt.subplot(1, 1) for rate in [0.1 * x for x in range(10, -1, -1)]: plt.plot(range(0, 5), range(0, 5), color="r", alpha=rate) plt.pause(0.1) plt.sho
import matplotlib.pyplot as plt
fig = plt.subplot(1, 1)
for rate in [0.1 * x for x in range(10, -1, -1)]:
plt.plot(range(0, 5), range(0, 5), color="r", alpha=rate)
plt.pause(0.1)
plt.show()
这个示例代码的目的是,随着处理的进行,我希望减少alpha值,并使行消失
有人知道解决这个问题的方法吗?
谢谢。您可以使用
set\u alpha
方法更新现有Line2D
的alpha值。其想法是绘制一次直线,然后更新循环中的alpha
import matplotlib.pyplot as plt
fig = plt.subplot(111)
plt.ion()
line, = plt.plot(range(0, 5), range(0, 5), color="r", alpha=1)
for rate in [0.1 * x for x in range(10, -1, -1)]:
line.set_alpha(rate)
plt.draw()
plt.pause(0.1)
plt.ioff()
plt.show()
我认为,您希望单独控制每个点的
alpha
值,因此我开始这样做(基于):
将numpy导入为np
将matplotlib.pyplot作为plt导入
将matplotlib.animation导入为动画
从matplotlib.collections导入LineCollection
类消失线(对象):
定义初始值(自身、n点、尾部长度、rgb颜色):
self.n_点=int(n_点)
self.tail\u length=int(tail\u length)
self.rgb_color=rgb_color
def set_数据(自身,x=无,y=无):
如果x为无或y为无:
self.lc=LineCollection([])
其他:
#确保我们一开始的分数不会超过我们想要的
x=x[-self.n_点:]
y=y[-self.n_点:]
#创建具有形状(len(x)、1、2)的点列表
#数组([[x0,y0]],
#[[x1,y1]],
# ...,
#[[xn,yn]]]
self.points=np.array([x,y]).T.reformate(-1,1,2)
#将每个点与后面的一个点分组(形状(len(x)-1,2,2)):
#数组([[x0,y0],
#[x1,y1]],
#[[x1,y1],
#[x2,y2]],
# ...
self.segments=np.concatenate([self.points[:-1],self.points[1:],
轴=1)
如果hasattr(self,“alphas”):
del self.alphas
如果hasattr(self,'rgba_colors'):
del self.rgba_颜色
#self.lc=LineCollection(self.segments,colors=self.get\u colors())
self.lc.set_段(self.segments)
self.lc.set\u color(self.get\u colors())
def get_LineCollection(自身):
如果不是hasattr(self,'lc'):
self.set_data()
返回自我信用证
def添加点(自身、x、y):
如果不是hasattr(self,“points”):
self.set_数据([x],[y])
其他:
#TODO:可以使用循环缓冲区来减少内存操作。。。
self.segments=np.concatenate((self.segments,[[self.points[-1][0],[x,y]]))
self.points=np.concatenate((self.points,[[[x,y]]]))
#如有必要,请删除点:
而len(self.points)>self.n_点:
self.segments=self.segments[1:]
self.points=self.points[1:]
self.lc.set_段(self.segments)
self.lc.set\u color(self.get\u colors())
def get_alphas(自身):
n=长度(自身点)
如果n
它应该绘制一个带有消失线的图形(使用提示保存,并从mp4在线转换为gif):
保存图形时,python实时显示的动画的开头似乎有一个bug,因为从[10,0]到第一个点出现了一条线
该行不会出现在保存的动画中,如果对要保存到图形的两行进行注释,则该行将消失
我相信动画保存是在动画显示之前运行的,因此保存运行的最后一点显示在显示运行的开始处。谢谢!这是否意味着如果我想更改alpha值超过两个(我是说,超过两条不同的线),我必须保持每一条“线”吗对象?是的,但您可以将它们存储在列表中,并在列表上循环,因此实际上不需要太多的代码。如果您想更改图形中所有行的alpha,也可以只循环
plt.gca().lines
。哦,您还可以…另外,如果是生成器,则默认情况下,保存程序将只保存100帧。不知道为什么,但您可以通过不使用生成器并直接在update函数上计算新值,以及通过给frames
一个ìnt`值来解决此问题。
import numpy as np
import matplotlib.pyplot as plt
import matplotlib.animation as animation
from matplotlib.collections import LineCollection
class Vanishing_Line(object):
def __init__(self, n_points, tail_length, rgb_color):
self.n_points = int(n_points)
self.tail_length = int(tail_length)
self.rgb_color = rgb_color
def set_data(self, x=None, y=None):
if x is None or y is None:
self.lc = LineCollection([])
else:
# ensure we don't start with more points than we want
x = x[-self.n_points:]
y = y[-self.n_points:]
# create a list of points with shape (len(x), 1, 2)
# array([[[ x0 , y0 ]],
# [[ x1 , y1 ]],
# ...,
# [[ xn , yn ]]])
self.points = np.array([x, y]).T.reshape(-1, 1, 2)
# group each point with the one following it (shape (len(x)-1, 2, 2)):
# array([[[ x0 , y0 ],
# [ x1 , y1 ]],
# [[ x1 , y1 ],
# [ x2 , y2 ]],
# ...
self.segments = np.concatenate([self.points[:-1], self.points[1:]],
axis=1)
if hasattr(self, 'alphas'):
del self.alphas
if hasattr(self, 'rgba_colors'):
del self.rgba_colors
#self.lc = LineCollection(self.segments, colors=self.get_colors())
self.lc.set_segments(self.segments)
self.lc.set_color(self.get_colors())
def get_LineCollection(self):
if not hasattr(self, 'lc'):
self.set_data()
return self.lc
def add_point(self, x, y):
if not hasattr(self, 'points'):
self.set_data([x],[y])
else:
# TODO: could use a circular buffer to reduce memory operations...
self.segments = np.concatenate((self.segments,[[self.points[-1][0],[x,y]]]))
self.points = np.concatenate((self.points, [[[x,y]]]))
# remove points if necessary:
while len(self.points) > self.n_points:
self.segments = self.segments[1:]
self.points = self.points[1:]
self.lc.set_segments(self.segments)
self.lc.set_color(self.get_colors())
def get_alphas(self):
n = len(self.points)
if n < self.n_points:
rest_length = self.n_points - self.tail_length
if n <= rest_length:
return np.ones(n)
else:
tail_length = n - rest_length
tail = np.linspace(1./tail_length, 1., tail_length)
rest = np.ones(rest_length)
return np.concatenate((tail, rest))
else: # n == self.n_points
if not hasattr(self, 'alphas'):
tail = np.linspace(1./self.tail_length, 1., self.tail_length)
rest = np.ones(self.n_points - self.tail_length)
self.alphas = np.concatenate((tail, rest))
return self.alphas
def get_colors(self):
n = len(self.points)
if n < 2:
return [self.rgb_color+[1.] for i in xrange(n)]
if n < self.n_points:
alphas = self.get_alphas()
rgba_colors = np.zeros((n, 4))
# first place the rgb color in the first three columns
rgba_colors[:,0:3] = self.rgb_color
# and the fourth column needs to be your alphas
rgba_colors[:, 3] = alphas
return rgba_colors
else:
if hasattr(self, 'rgba_colors'):
pass
else:
alphas = self.get_alphas()
rgba_colors = np.zeros((n, 4))
# first place the rgb color in the first three columns
rgba_colors[:,0:3] = self.rgb_color
# and the fourth column needs to be your alphas
rgba_colors[:, 3] = alphas
self.rgba_colors = rgba_colors
return self.rgba_colors
def data_gen(t=0):
"works like an iterable object!"
cnt = 0
while cnt < 1000:
cnt += 1
t += 0.1
yield t, np.sin(2*np.pi*t) * np.exp(-t/100.)
def update(data):
"Update the data, receives whatever is returned from `data_gen`"
x, y = data
line.add_point(x, y)
# rescale the graph by large steps to avoid having to do it every time:
xmin, xmax = ax.get_xlim()
if x >= xmax:
ax.set_xlim(xmin, 2*xmax)
ax.figure.canvas.draw()
return line,
if __name__ == '__main__':
n_points = 100
tail_length = (3/4.)*n_points
rgb_color = [0., 0.5, 1.0]
time_pause = 0 # miliseconds
x=np.linspace(0, 4*np.pi, 2*n_points)
y=np.cos(x)
line = Vanishing_Line(n_points, tail_length, rgb_color)
fig, ax = plt.subplots()
ax.add_collection(line.get_LineCollection())
ax.set_xlim(0, 4*np.pi)
ax.set_ylim(-1.1,1.1)
ani = animation.FuncAnimation(fig, update, data_gen, blit=False,
interval=time_pause, repeat=False)
fig.show()
mywriter = animation.FFMpegWriter(fps=30)
ani.save('ani.mp4', writer=mywriter, dpi=600)