Python Matplotlib.text.OffsetFrom用法及代码示例

Matplotlib是Python中令人惊叹的可视化库，用于数组的二维图。 Matplotlib是一个基于NumPy数组的多平台数据可视化库，旨在与更广泛的SciPy堆栈配合使用。

matplotlib.text.OffsetFrom

这个matplotlib.text.OffsetFrom class是用于处理批注的可调用帮助程序类。

用法： class matplotlib.text.OffsetFrom(artist, ref_coord, unit=’points’)

参数：

artist:该对象用于计算偏移量。它通常是Artist，BboxBase或Transform。
ref_coord:是长度2序列。如果是Artist或BboxBase，则此值是偏移量原点到位置的偏移量(以艺术家边界框的分数为单位)，而如果Artist是Transform，则该偏移量原点是应用于此值的变换。
unit:它用于管理要用于偏移输入的屏幕单位(像素或点)。

该类的方法：

get_unit(self):它是__call__使用的转换输入的单位。
set_unit(self, unit):它是__call__使用的转换输入的单位，其中，单位参数在‘points’或‘pixels’中。

范例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()

输出：

范例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()

输出：

相关用法

注：本文由纯净天空筛选整理自RajuKumar19大神的英文原创作品 Matplotlib.text.OffsetFrom class in python。非经特殊声明，原始代码版权归原作者所有，本译文未经允许或授权，请勿转载或复制。