确定matplotlib轴大小(以像素为单位)

Question

给定matplotlib中的一组轴,有没有办法确定其大小(以像素为单位)？我需要根据对更大或更小数字的调整来扩展事物.

(特别是我想改变线宽,使其与轴尺寸成比例.)

Answer 1

这给出了以英寸为单位的宽度和高度.

bbox = ax.get_window_extent().transformed(fig.dpi_scale_trans.inverted())
width, height = bbox.width, bbox.height

这可能足以满足您的目的,但要获得像素,您可以乘以fig.dpi:

width *= fig.dpi
height *= fig.dpi

例如,

import matplotlib.pyplot as plt

def get_ax_size(ax):
    bbox = ax.get_window_extent().transformed(fig.dpi_scale_trans.inverted())
    width, height = bbox.width, bbox.height
    width *= fig.dpi
    height *= fig.dpi
    return width, height

fig, ax = plt.subplots()
print(get_ax_size(ax))
#(496.0, 384.00000000000006)

ax2 = plt.axes([0.3, 0.3, 0.7, 0.7])
print(get_ax_size(ax2))
# (448.0, 336.0)

要制作完全相同图形尺寸的图像,您必须删除图形和轴之间的空白:

import numpy as np
import matplotlib.pyplot as plt

def get_ax_size(ax):
    bbox = ax.get_window_extent().transformed(fig.dpi_scale_trans.inverted())
    width, height = bbox.width, bbox.height
    width *= fig.dpi
    height *= fig.dpi
    return width, height

data = np.arange(9).reshape((3, 3))
fig = plt.figure(figsize=(8,6), dpi=80)
ax = plt.Axes(fig, [0., 0., 1., 1.])
ax.set_axis_off()
fig.add_axes(ax)
ax.imshow(data, aspect='equal')
print(get_ax_size(ax))
# (640.0, 480.0)
plt.savefig('/tmp/test.png', dpi=80)

% identify /tmp/test.png
/tmp/test.png PNG 640x480 640x480+0+0 8-bit DirectClass 50.5KB 0.020u 0:00.020