python - 消息 "Matplotlib is currently using agg"和 Matplotlib 不显示图像

Question

其他人有这个问题，我用了他们的解决方案但没有解决。

我用 virtual env with python3.5 .Matplotlib安装在 virtual env 下.
我在系统上安装了 python3.tkinter。

当我检查

matplotlib.get_backend()

我有

>>> import matplotlib
>>> matplotlib.get_backend()
'TkAgg'

但是当我运行下面的代码时

for image_path in TEST_IMAGE_PATHS:
  image = Image.open(image_path)
  # the array based representation of the image will be used later in order to prepare the
  # result image with boxes and labels on it.
  image_np = load_image_into_numpy_array(image)
  # Expand dimensions since the model expects images to have shape: [1, None, None, 3]
  image_np_expanded = np.expand_dims(image_np, axis=0)
  # Actual detection.
  output_dict = run_inference_for_single_image(image_np, detection_graph)
  # Visualization of the results of a detection.
  vis_util.visualize_boxes_and_labels_on_image_array(
      image_np,
      output_dict['detection_boxes'],
      output_dict['detection_classes'],
      output_dict['detection_scores'],
      category_index,
      instance_masks=output_dict.get('detection_masks'),
      use_normalized_coordinates=True,
      line_thickness=8)
  #plt.figure(figsize=IMAGE_SIZE)
  plt.imshow(image_np)
  plt.show()

我有问题

 UserWarning: Matplotlib is currently using agg, which is a non-GUI backend, so cannot show the figure.
  % get_backend())

我把标题放在

from io import StringIO
import matplotlib
matplotlib.rcParams["backend"] = "TkAgg"
from matplotlib import pyplot as plt
from PIL import Image

有人说解决了，但我还是和plt一样的问题不显示图像。

Answer 1

如 you noted , Matplotlib 后端 sometimes require extra steps to run in virtual environments .

话虽如此，上面链接的文档也表明 TkAgg 应该可用:

[...] the Tk framework (TkAgg backend) does not require any external dependencies and is normally always available.

我使用 Ubuntu，并且我认为 TkAgg 将依赖于 PyGObject。该选项本身有一个注释，链接到构建说明。

关注 PyGObject build instructions ，我去安装它的系统dependencies :

sudo apt-get install -y python3-venv python3-wheel python3-dev
sudo apt-get install -y libgirepository1.0-dev build-essential \
  libbz2-dev libreadline-dev libssl-dev zlib1g-dev libsqlite3-dev wget \
  curl llvm libncurses5-dev libncursesw5-dev xz-utils tk-dev libcairo2-dev

然后添加了以下Python dependencies到我项目的虚拟环境:

pycairo

pygobject

# inside my project's virtual environment
pip install pycairo
pip install pygobject

完成后，像往常一样运行我的项目会显示预期的图形。

笔记

我在项目的虚拟环境中使用 Ubuntu 18.04.2 和 Python 3.6.8。

我跳过了 PyGObject 的大部分构建指令，只做了我上面描述的。