使用 Matplotlib 创建标志

简介

本实验将指导你使用 Python 的 Matplotlib 库创建 Firefox 标志的过程。

虚拟机提示

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导入所需库

我们将首先导入此项目所需的所有库，其中包括 re、matplotlib.pyplot、numpy、matplotlib.patches 和 matplotlib.path。

import re
import matplotlib.pyplot as plt
import numpy as np
import matplotlib.patches as patches
from matplotlib.path import Path

定义Firefox标志路径

我们将使用SVG路径数据定义Firefox标志的路径。

firefox = "M28.4,22.469c0.479-0.964,0.851-1.991,1.095-3.066c0.953-3.661,0.666-6.854,0.666-6.854l-0.327,2.104c0,0-0.469-3.896-1.044-5.353c-0.881-2.231-1.273-2.214-1.274-2.21c0.542,1.379,0.494,2.169,0.483,2.288c-0.01-0.016-0.019-0.032-0.027-0.047c-0.131-0.324-0.797-1.819-2.225-2.878c-2.502-2.481-5.943-4.014-9.745-4.015c-4.056,0-7.705,1.745-10.238,4.525C5.444,6.5,5.183,5.938,5.159,5.317c0,0-0.002,0.002-0.006,0.005c0-0.011-0.003-0.021-0.003-0.031c0,0-1.61,1.247-1.436,4.612c-0.299,0.574-0.56,1.172-0.777,1.791c-0.375,0.817-0.75,2.004-1.059,3.746c0,0,0.133-0.422,0.399-0.988c-0.064,0.482-0.103,0.971-0.116,1.467c-0.09,0.845-0.118,1.865-0.039,3.088c0,0,0.032-0.406,0.136-1.021c0.834,6.854,6.667,12.165,13.743,12.165l0,0c1.86,0,3.636-0.37,5.256-1.036C24.938,27.771,27.116,25.196,28.4,22.469zM16.002,3.356c2.446,0,4.73,0.68,6.68,1.86c-2.274-0.528-3.433-0.261-3.423-0.248c0.013,0.015,3.384,0.589,3.981,1.411c0,0-1.431,0-2.856,0.41c-0.065,0.019,5.242,0.663,6.327,5.966c0,0-0.582-1.213-1.301-1.42c0.473,1.439,0.351,4.17-0.1,5.528c-0.058,0.174-0.118-0.755-1.004-1.155c0.284,2.037-0.018,5.268-1.432,6.158c-0.109,0.07,0.887-3.189,0.201-1.93c-4.093,6.276-8.959,2.539-10.934,1.208c1.585,0.388,3.267,0.108,4.242-0.559c0.982-0.672,1.564-1.162,2.087-1.047c0.522,0.117,0.87-0.407,0.464-0.872c-0.405-0.466-1.392-1.105-2.725-0.757c-0.94,0.247-2.107,1.287-3.886,0.233c-1.518-0.899-1.507-1.63-1.507-2.095c0-0.366,0.257-0.88,0.734-1.028c0.58,0.062,1.044,0.214,1.537,0.466c0.005-0.135,0.006-0.315-0.001-0.519c0.039-0.077,0.015-0.311-0.047-0.596c-0.036-0.287-0.097-0.582-0.19-0.851c0.01-0.002,0.017-0.007,0.021-0.021c0.076-0.344,2.147-1.544,2.299-1.659c0.153-0.114,0.55-0.378,0.506-1.183c-0.015-0.265-0.058-0.294-2.232-0.286c-0.917,0.003-1.425-0.894-1.589-1.245c0.222-1.231,0.863-2.11,1.919-2.704c0.02-0.011,0.015-0.021-0.008-0.027c0.219-0.127-2.524-0.006-3.76,1.604C9.674,8.045,9.219,7.95,8.71,7.95c-0.638,0-1.139,0.07-1.603,0.187c-0.05,0.013-0.122,0.011-0.208-0.001C6.769,8.04,6.575,7.88,6.365,7.672c0.161-0.18,0.324-0.356,0.495-0.526C9.201,4.804,12.43,3.357,16.002,3.356z"  ## noqa

解析SVG路径数据

我们将使用 svg_parse 函数把SVG路径数据解析为顶点和代码，以便Matplotlib使用。

def svg_parse(path):
    commands = {'M': (Path.MOVETO,),
                'L': (Path.LINETO,),
                'Q': (Path.CURVE3,)*2,
                'C': (Path.CURVE4,)*3,
                'Z': (Path.CLOSEPOLY,)}
    vertices = []
    codes = []
    cmd_values = re.split("([A-Za-z])", path)[1:]  ## 按命令分割。
    for cmd, values in zip(cmd_values[::2], cmd_values[1::2]):
        ## 数字由逗号或 +/- 符号分隔（但不在字符串开头）。
        points = ([*map(float, re.split(",|(?<!^)(?=[+-])", values))] if values
                  else [(0., 0.)])  ## 仅用于 "z/Z"（CLOSEPOLY）。
        points = np.reshape(points, (-1, 2))
        if cmd.islower():
            points += vertices[-1][-1]
        codes.extend(commands[cmd.upper()])
        vertices.append(points)
    return np.array(codes), np.concatenate(vertices)

## 解析Firefox标志路径数据
codes, verts = svg_parse(firefox)
path = Path(verts, codes)

创建绘图

现在我们将使用Matplotlib创建绘图，方法是向绘图中添加两个 PathPatch 对象。一个将是橙色填充形状，另一个将是白色轮廓。

## 设置绘图界限
xmin, ymin = verts.min(axis=0) - 1
xmax, ymax = verts.max(axis=0) + 1

## 创建绘图
fig = plt.figure(figsize=(5, 5), facecolor="0.75")  ## 灰色背景
ax = fig.add_axes([0, 0, 1, 1], frameon=False, aspect=1,
                  xlim=(xmin, xmax),  ## 居中
                  ylim=(ymax, ymin),  ## 居中，上下颠倒
                  xticks=[], yticks=[])  ## 无刻度

## 添加白色轮廓
ax.add_patch(patches.PathPatch(path, facecolor='none', edgecolor='w', lw=6))

## 添加橙色形状
ax.add_patch(patches.PathPatch(path, facecolor='orange', edgecolor='k', lw=2))

## 显示绘图
plt.show()

总结

在这个实验中，我们学习了如何使用Matplotlib创建Firefox标志的绘图。我们使用一个自定义函数解析了SVG路径数据，并使用 PathPatch 对象创建了绘图。这个实验很好地介绍了Matplotlib在创建复杂形状和设计方面的能力。