如何以交互方式更新 matplotlib 的 imshow() 窗口? [英] How to update matplotlib's imshow() window interactively?

问题描述

我正在研究一些计算机视觉算法，我想展示一个 numpy 数组在每一步中是如何变化的.

I'm working on some computer vision algorithm and I'd like to show how a numpy array changes in each step.

现在有效的是，如果我的代码末尾有一个简单的 imshow( array )，窗口将显示并显示最终图像.

What works now is that if I have a simple imshow( array ) at the end of my code, the window displays and shows the final image.

但是我想做的是随着图像在每次迭代中的变化而更新和显示 imshow 窗口.

However what I'd like to do is to update and display the imshow window as the image changes in each iteration.

例如我想做:

import numpy as np
import matplotlib.pyplot as plt
import time

array = np.zeros( (100, 100), np.uint8 )

for i in xrange( 0, 100 ):
    for j in xrange( 0, 50 ):
        array[j, i] = 1

        #_show_updated_window_briefly_
        plt.imshow( array )
        time.sleep(0.1)

问题是这样的话，Matplotlib 窗口不会被激活，只有在整个计算完成后才被激活.

The problem is that this way, the Matplotlib window doesn't get activated, only once the whole computation is finished.

我已经尝试过原生 matplotlib 和 pyplot，但结果是一样的.对于绘图命令，我发现了一个 .ion() 开关，但在这里它似乎不起作用.

I've tried both native matplotlib and pyplot, but the results are the same. For plotting commands I found an .ion() switch, but here it doesn't seem to work.

第一季度.连续显示 numpy 数组(实际上是 uint8 灰度图像)更新的最佳方法是什么?

Q1. What is the best way to continuously display updates to a numpy array (actually a uint8 greyscale image)?

第 2 季度.是否可以使用动画函数来做到这一点，例如 动态图像示例?我想在循环内调用一个函数，因此我不知道如何使用动画函数来实现这一点.

Q2. Is it possible to do this with an animation function, like in the dynamic image example? I'd like to call a function inside a loop, thus I don't know how to achieve this with an animation function.

推荐答案

你不需要一直调用 imshow.使用对象的 set_data 方法要快得多:

You don't need to call imshow all the time. It is much faster to use the object's set_data method:

myobj = imshow(first_image)
for pixel in pixels:
    addpixel(pixel)
    myobj.set_data(segmentedimg)
    draw()

draw() 应该确保后端更新图像.

The draw() should make sure that the backend updates the image.

更新:您的问题已被显着修改.在这种情况下，最好再问一个问题.这是处理第二个问题的方法:

UPDATE: your question was significantly modified. In such cases it is better to ask another question. Here is a way to deal with your second question:

Matplotlib 的动画只处理一个增加的维度(时间)，所以你的双循环不会做.您需要将索引转换为单个索引.下面是一个例子:

Matplotlib's animation only deals with one increasing dimension (time), so your double loop won't do. You need to convert your indices to a single index. Here is an example:

import numpy as np
from matplotlib import pyplot as plt
from matplotlib import animation

nx = 150
ny = 50

fig = plt.figure()
data = np.zeros((nx, ny))
im = plt.imshow(data, cmap='gist_gray_r', vmin=0, vmax=1)

def init():
    im.set_data(np.zeros((nx, ny)))

def animate(i):
    xi = i // ny
    yi = i % ny
    data[xi, yi] = 1
    im.set_data(data)
    return im

anim = animation.FuncAnimation(fig, animate, init_func=init, frames=nx * ny,
                               interval=50)

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