python画矩形框

在Python中，通常使用matplotlib、PIL（Pillow）或OpenCV等库来绘制矩形框。这里给出一些基本的例子：

1. **使用matplotlib**：

import matplotlib.pyplot as plt
import numpy as np

def draw_rectangle(x, y, width, height, ax=None):
    if ax is None:
        fig, ax = plt.subplots()
    rect = patches.Rectangle((x, y), width, height, fill=False, edgecolor='red', linewidth=2)
    ax.add_patch(rect)
    ax.set_xlim([0, width+width])
    ax.set_ylim([0, height+height])
    return ax

# 示例
ax = draw_rectangle(50, 75, 100, 50)
plt.show()

2. **使用PIL（Pillow）**，对于图像操作更为方便：

from PIL import Image, ImageDraw, ImageFont

def draw_rectangle(image, x, y, width, height, color=(255, 0, 0)):
    draw = ImageDraw.Draw(image)
    draw.rectangle([(x, y), (x + width, y + height)], outline=color)
    del draw
    return image

# 示例
image = Image.new("RGB", (400, 400), "white")
rect_image = draw_rectangle(image, 50, 50, 100, 100)
rect_image.show()

3. **使用OpenCV**:

import cv2

def draw_rectangle_on_image(img, pt1, pt2, color=(0, 0, 255), thickness=2):
    cv2.rectangle(img, pt1, pt2, color, thickness)
    return img

# 示例
img = np.zeros((400, 400, 3), dtype=np.uint8)
pt1 = (50, 50)
pt2 = (150, 150)
result_img = draw_rectangle_on_image(img, pt1, pt2)
cv2.imshow('Rectangle', result_img)
cv2.waitKey(0)
cv2.destroyAllWindows()

以上代码分别展示了如何在图形窗口、图像文件以及OpenCV的BGR图片上绘制矩形框。