确定matplotlib轴大小(以像素为单位) [英] determine matplotlib axis size in pixels

问题描述

给定matplotlib中的一组轴，有没有办法确定其大小(以像素为单位) ?我需要按比例缩放以适应更大或更小的数字.

Given a set of axes in matplotlib, is there a way to determine its size in pixels? I need to scale things according to adjust for larger or smaller figures.

(特别是我想更改线宽，使其与轴的大小成比例.)

(In particular I want to change the linewidth so it is proportionate for the axes size.)

推荐答案

这给出了以英寸为单位的宽度和高度.

This gives the width and height in inches.

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

这可能满足您的目的，但是要获得像素，可以乘以fig.dpi:

That probably suffices for your purpose, but to get pixels, you can multiply by fig.dpi:

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

---

例如，

---

For example,

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)

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要制作与该图大小完全相同的图像，您必须删除两个图和轴:

---

To make an image of exactly that figure size, you have to remove whitespace between the figure and the axis:

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

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