Matplotlib是Python中令人驚歎的可視化庫，用於數組的二維圖。 Matplotlib是一個基於NumPy數組的多平台數據可視化庫，旨在與更廣泛的SciPy堆棧配合使用。
matplotlib.text.OffsetFrom
這個matplotlib.text.OffsetFrom class是用於處理批注的可調用幫助程序類。
用法： class matplotlib.text.OffsetFrom(artist, ref_coord, unit=’points’)
參數：
- artist:該對象用於計算偏移量。它通常是Artist，BboxBase或Transform。
- ref_coord:是長度2序列。如果是Artist或BboxBase，則此值是偏移量原點到位置的偏移量(以藝術家邊界框的分數為單位)，而如果Artist是Transform，則該偏移量原點是應用於此值的變換。
- unit:它用於管理要用於偏移輸入的屏幕單位(像素或點)。
該類的方法：
- get_unit(self):它是__call__使用的轉換輸入的單位。
- set_unit(self, unit):它是__call__使用的轉換輸入的單位，其中，單位參數在‘points’或‘pixels’中。
範例1：
import matplotlib.pyplot as plt
import matplotlib.text
fig, ax = plt.subplots()
ax.plot([5,1], label="Label 1")
ax.plot([3,0], label="Label 2")
legend = ax.legend(loc="upper right")
# Create offset from lower right
# corner of legend box, (1.0,0) is
# the coordinates of the offset point
# in the legend coordinate system
offset = matplotlib.text.OffsetFrom(legend, (1.0, 0.0))
# Create annotation. Top right corner
# located -20 pixels below the offset
# point (lower right corner of legend).
ax.annotate("info_string",
xy = (0,0),
size = 14,
xycoords = 'figure fraction',
xytext = (0,-20),
textcoords = offset,
horizontalalignment = 'right',
verticalalignment = 'top')
# Draw the canvas for offset to take effect
fig.canvas.draw()
plt.show()輸出：
範例2：
import matplotlib.pyplot as plt
from matplotlib.patches import Ellipse
import numpy as np
from matplotlib.text import OffsetFrom
fig, (ax1, ax2) = plt.subplots(1, 2)
bbox_args = dict(boxstyle ="round", fc ="0.8")
arrow_args = dict(arrowstyle ="->")
# Here we'll demonstrate the extents of the coordinate system and how
# we place annotating text.
ax1.annotate('figure fraction:0, 0',
xy =(0, 0),
xycoords ='figure fraction',
xytext =(20, 20),
textcoords ='offset points',
ha = "left",
va = "bottom",
bbox = bbox_args,
arrowprops = arrow_args)
ax1.annotate('figure fraction:1, 1',
xy =(1, 1),
xycoords ='figure fraction',
xytext = (-20, -20),
textcoords ='offset points',
ha = "right",
va = "top",
bbox = bbox_args,
arrowprops = arrow_args)
ax1.annotate('axes fraction:0, 0',
xy = (0, 0),
xycoords ='axes fraction',
xytext = (20, 20),
textcoords ='offset points',
ha = "left",
va = "bottom",
bbox = bbox_args,
arrowprops = arrow_args)
ax1.annotate('axes fraction:1, 1',
xy =(1, 1),
xycoords ='axes fraction',
xytext = (-20, -20),
textcoords ='offset points',
ha = "right",
va = "top",
bbox = bbox_args,
arrowprops = arrow_args)
# It is also possible to generate
# draggable annotations
an1 = ax1.annotate('Drag me 1', xy =(.5, .7),
xycoords ='data',
ha ="center", va ="center",
bbox = bbox_args,
)
an2 = ax1.annotate('Drag me 2', xy =(.5, .5),
xycoords = an1,
xytext =(.5, .3),
textcoords = 'axes fraction',
ha = "center",
va = "center",
bbox = bbox_args,
arrowprops = dict(patchB = an1.get_bbox_patch(),
connectionstyle = "arc3, rad = 0.2",
**arrow_args))
an1.draggable()
an2.draggable()
an3 = ax1.annotate('', xy =(.5, .5), xycoords = an2,
xytext =(.5, .5), textcoords = an1,
ha ="center", va ="center",
bbox = bbox_args,
arrowprops = dict(patchA = an1.get_bbox_patch(),
patchB = an2.get_bbox_patch(),
connectionstyle ="arc3, rad = 0.2",
**arrow_args))
# Finally we'll show off some more
# complex annotation and placement
text = ax2.annotate('xy =(0, 1)\nxycoords = ("data", "axes fraction")',
xy =(0, 1),
xycoords = ("data", 'axes fraction'),
xytext = (0, -20),
textcoords ='offset points',
ha = "center",
va = "top",
bbox = bbox_args,
arrowprops = arrow_args)
ax2.annotate('xy =(0.5, 0)\nxycoords = artist',
xy =(0.5, 0.),
xycoords = text,
xytext = (0, -20),
textcoords = 'offset points',
ha = "center",
va = "top",
bbox = bbox_args,
arrowprops = arrow_args)
ax2.annotate('xy =(0.8, 0.5)\nxycoords = ax1.transData',
xy =(0.8, 0.5),
xycoords = ax1.transData,
xytext = (10, 10),
textcoords = OffsetFrom(ax2.bbox, (0, 0), "points"),
ha = "left",
va = "bottom",
bbox = bbox_args,
arrowprops = arrow_args)
ax2.set(xlim =[-2, 2], ylim =[-2, 2])
plt.show()輸出：
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注：本文由純淨天空篩選整理自RajuKumar19大神的英文原創作品 Matplotlib.text.OffsetFrom class in python。非經特殊聲明，原始代碼版權歸原作者所有，本譯文未經允許或授權，請勿轉載或複製。