如何从绘图（Matplotlib）中获取 uint8 类型的图像？

Question

考虑这段代码：

fig = Figure()
canvas = FigureCanvas(fig)
ax = fig.gca()

ax.text(0.0,0.0,"Test", fontsize=45)
ax.axis('off')
canvas.draw()       # draw the canvas, cache the renderer
width, height = fig.get_size_inches() * fig.get_dpi()
images = np.fromstring(canvas.tostring_rgb(), dtype='uint8').reshape(int(height), int(width), 3)

所以我遇到的问题是它保存了带有文本“测试”的情节。但是假设我有一个图，确切地说是“AxesImages”matplotlib，我怎样才能转换图像图而不是文本？我试图用 ax.imshow(axesImage) 更改 ax.text(...) 但它抛出错误。

有什么建议吗？

Answer 1

您可以将图像保存到文件中，然后使用 PIL 将文件加载到数组中：

from PIL import Image
import numpy as np
import matplotlib.pyplot as plt

fig, ax = plt.subplots()
ax.text(0.0,0.0,"Test", fontsize=45)
ax.axis('off')
ax.imshow(np.random.random((3,3)))
filename = '/tmp/out.png'
fig.savefig(filename)
img = Image.open(filename).convert('RGB')
arr = np.asarray(img)
img.show()

如果你想避免磁盘 I/O，你可以save the image to a BytesIO object instead:

import io
from PIL import Image
import numpy as np
import matplotlib.pyplot as plt

fig, ax = plt.subplots()
ax.text(0.0,0.0,"Test", fontsize=45)
ax.axis('off')
ax.imshow(np.random.random((3,3)))

with io.BytesIO() as memf:
    fig.savefig(memf, format='PNG')
    memf.seek(0)
    img = Image.open(memf)
    arr = np.asarray(img)
    img.show()