Question

我有几张图片可以显示某些事情的变化。我使用以下代码在同一块图上将它们可视化为多个图像：

import matplotlib.pyplot as plt
import matplotlib.cm as cm

img = [] # some array of images
fig = plt.figure()
for i in xrange(6):
    fig.add_subplot(2, 3, i + 1)
    plt.imshow(img[i], cmap=cm.Greys_r)

plt.show()

并得到类似：

的内容

哪个好，但我宁愿让它们动画以获得something like this video。我如何使用python实现这一点，最好（不一定）使用matplotlib

Answer 1

对于未来我自己，这就是我最终的目标：

def generate_video(img):
    for i in xrange(len(img)):
        plt.imshow(img[i], cmap=cm.Greys_r)
        plt.savefig(folder + "/file%02d.png" % i)

    os.chdir("your_folder")
    subprocess.call([
        'ffmpeg', '-framerate', '8', '-i', 'file%02d.png', '-r', '30', '-pix_fmt', 'yuv420p',
        'video_name.mp4'
    ])
    for file_name in glob.glob("*.png"):
        os.remove(file_name)

Answer 2

您可以使用plt.savefig("file%d.png" % i)将图像导出到png，然后使用ffmpeg生成视频。

Here you find help to generate video from images

Answer 3

我实现了一个方便的脚本，适合你和新来的人。试一试here。

对于你的例子：

imagelist = YOUR-IMAGE-LIST
def redraw_fn(f, axes):
    img = imagelist[f]
    if not redraw_fn.initialized:
        redraw_fn.im = axes.imshow(img, animated=True)
        redraw_fn.initialized = True
    else:
        redraw_fn.im.set_array(img)
redraw_fn.initialized = False

videofig(len(imagelist), redraw_fn, play_fps=30)

Answer 4

另一种解决方案是使用animated image demo中所述的AnimationArtist中的matplotlib.animation。适应您的示例将是

import matplotlib.pyplot as plt
import matplotlib.cm as cm

img = [] # some array of images
frames = [] # for storing the generated images
fig = plt.figure()
for i in xrange(6):
    frames.append([plt.imshow(img[i], cmap=cm.Greys_r,animated=True)])

ani = animation.ArtistAnimation(fig, ims, interval=50, blit=True,
                                repeat_delay=1000)
# ani.save('movie.mp4')
plt.show()

Answer 5

您可以尝试延迟顺序绘制图像（帧）。如果您有很多帧，可以在plt.pause()函数中减少帧之间的等待时间。

# need this line if you're using jupyter notebooks
%matplotlib notebook

x = [] # Some array of images
fig = plt.figure()
viewer = fig.add_subplot(111)
plt.ion() # Turns interactive mode on (probably unnecessary)
fig.show() # Initially shows the figure

for i in range(len(x)):
    viewer.clear() # Clears the previous image
    viewer.imshow(x[i]) # Loads the new image
    plt.pause(.1) # Delay in seconds
    fig.canvas.draw() # Draws the image to the screen

Answer 6

您可以使用Agg界面从matplotlib导出图像。

请参见这些示例：

这是您的完整代码：

# imports
import matplotlib.pyplot as plt
import matplotlib.cm as cm
import cv2

# Use Agg backend for canvas
from matplotlib.backends.backend_agg import FigureCanvasAgg as FigureCanvas

# create OpenCV video writer
video = cv2.VideoWriter('video.mp4', cv2.VideoWriter_fourcc('A','V','C','1'), 1, (mat.shape[0],mat.shape[1]))

# loop over your images
for i in xrange(len(img)):

    fig = plt.figure()
    plt.imshow(img[i], cmap=cm.Greys_r)

    # put pixel buffer in numpy array
    canvas = FigureCanvas(fig)
    canvas.draw()
    mat = np.array(canvas.renderer._renderer)
    mat = cv2.cvtColor(mat, cv2.COLOR_RGB2BGR)

    # write frame to video
    video.write(mat)

# close video writer
cv2.destroyAllWindows()
video.release()

Answer 7

这是一个可复制粘贴的函数，如果您正在处理长视频并且正在使用流式迭代器（来自 here），这很方便

from typing import Iterator, Optional, Tuple
from pathlib import Path

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


def write_animation(
    itr: Iterator[np.array],
    out_file: Path,
    dpi: int = 50,
    fps: int = 30,
    title: str = "Animation",
    comment: Optional[str] = None,
    writer: str = "ffmpeg",
) -> None:
    """Function that writes an animation from a stream of input tensors.

    Args:
        itr: The image iterator, yielding images with shape (H, W, C).
        out_file: The path to the output file.
        dpi: Dots per inch for output image.
        fps: Frames per second for the video.
        title: Title for the video metadata.
        comment: Comment for the video metadata.
        writer: The Matplotlib animation writer to use (if you use the
            default one, make sure you have `ffmpeg` installed on your
            system).
    """

    first_img = next(itr)
    height, width, _ = first_img.shape
    fig, ax = plt.subplots(figsize=(width / dpi, height / dpi))

    # Ensures that there's no extra space around the image.
    fig.subplots_adjust(
        left=0,
        bottom=0,
        right=1,
        top=1,
        wspace=None,
        hspace=None,
    )

    # Creates the writer with the given metadata.
    Writer = mpl.animation.writers[writer]
    metadata = {
        "title": title,
        "artist": __name__,
        "comment": comment,
    }
    mpl_writer = Writer(
        fps=fps,
        metadata={k: v for k, v in metadata.items() if v is not None},
    )

    with mpl_writer.saving(fig, out_file, dpi=dpi):
        im = ax.imshow(first_img, interpolation="nearest")
        mpl_writer.grab_frame()

        for img in itr:
            im.set_data(img)
            mpl_writer.grab_frame()

如何在matplotlib中从图像阵列制作视频？

7 个答案: