如何在Python的Matplotlib中为每个1×1像素添加边框并标注数值

我使用Python的Matplotlib编写了以下代码生成图像，现咨询如何为每个1×1像素添加边框，以及如何添加数组中对应的像素网格编号？

import matplotlib.pyplot as plt
import numpy as np
fig, ax = plt.subplots()
ax.set_title('Satellite 1')
grid=np.array(
[
[
1,1,2,2,3,3,4,4,5,5,6,6,7,7,8,8,],
[
9,9,10,10,11,11,12,12,13,13,14,14,15,15,16,16,],
[
17,17,18,18,19,19,20,0,21,21,22,0,23,23,24,24,],
[
25,25,26,26,27,27,28,28,29,29,30,30,31,31,32,32,],
[
33,33,34,0,35,35,36,36,37,37,0,38,39,39,40,40,],
[
41,41,41,42,42,42,43,43,43,44,44,44,45,45,45,0,],
]
)

#ax.imshow(grid)
im = plt.imshow(grid, cmap='PuBuGn')

# Move left and bottom spines outward by 10 points
ax.spines['left'].set_position(('outward', 10))
ax.spines['bottom'].set_position(('outward', 10))

# Hide the right and top spines
ax.spines['right'].set_visible(True)
ax.spines['top'].set_visible(True)

# Only show ticks on the left and bottom spines
ax.yaxis.set_ticks_position('left')
ax.xaxis.set_ticks_position('bottom')
im.axes.get_xaxis().set_visible(True)
im.axes.get_yaxis().set_visible(True)
ax.set_frame_on(True)

ax.set_aspect('equal')

plt.colorbar(orientation='horizontal')

plt.show()

1. 为每个像素添加边框 #

利用Matplotlib的网格线功能，将网格线对齐到像素边缘即可实现边框效果，核心是调整刻度与网格的位置匹配：

• 设置x、y轴刻度为像素中心位置
• 开启网格线并设置样式，让网格线刚好落在像素边界
• 隐藏刻度线避免视觉干扰

2. 添加像素网格编号 #

遍历数组每个元素，在对应像素中心位置添加文本标注，可按需跳过值为0的元素：

• 双重循环遍历数组的行与列
• 使用ax.text()在像素中心写入对应编号，设置居中对齐与字体样式

完整修改代码 #

import matplotlib.pyplot as plt
import numpy as np
fig, ax = plt.subplots()
ax.set_title('Satellite 1')
grid=np.array(
[
[1,1,2,2,3,3,4,4,5,5,6,6,7,7,8,8,],
[9,9,10,10,11,11,12,12,13,13,14,14,15,15,16,16,],
[17,17,18,18,19,19,20,0,21,21,22,0,23,23,24,24,],
[25,25,26,26,27,27,28,28,29,29,30,30,31,31,32,32,],
[33,33,34,0,35,35,36,36,37,37,0,38,39,39,40,40,],
[41,41,41,42,42,42,43,43,43,44,44,44,45,45,45,0,],
]
)

# 绘制基础图像
im = plt.imshow(grid, cmap='PuBuGn')

# --- 添加像素边框 ---
ax.set_xticks(np.arange(grid.shape[1]))
ax.set_yticks(np.arange(grid.shape[0]))
ax.grid(color='black', linestyle='-', linewidth=0.5)
ax.tick_params(axis='both', which='both', length=0, labelleft=True, labelbottom=True)

# --- 添加网格编号 ---
for i in range(grid.shape[0]):
    for j in range(grid.shape[1]):
        val = grid[i, j]
        if val != 0:
            ax.text(j, i, str(val), ha='center', va='center', color='white', fontsize=8)

# 保留原有轴样式设置
ax.spines['left'].set_position(('outward', 10))
ax.spines['bottom'].set_position(('outward', 10))
ax.spines['right'].set_visible(True)
ax.spines['top'].set_visible(True)
ax.yaxis.set_ticks_position('left')
ax.xaxis.set_ticks_position('bottom')
ax.set_aspect('equal')

plt.colorbar(orientation='horizontal')
plt.show()

关键说明 #

• 边框实现：网格线通过刻度位置对齐，刚好覆盖每个像素的边缘，形成1×1的边框效果
• 编号添加：ax.text(j, i, ...)中，j对应列索引（x坐标）、i对应行索引（y坐标），ha和va参数确保文本在像素内居中，可根据需求调整字体大小、颜色

内容的提问来源于stack exchange，提问作者MO MO MA