python 解决OpenCV显示中文字符 存在的缺点：cv2->pil 中 Image.fromarray(img)存在耗时4~5ms。

因工作需要，要在图片中显示中文字符，并且要求速度足够快，在网上搜罗一番后，总结下几个解决方法。

1.方法一：转PIL后使用PIL相关函数添加中文字符

from PIL import Image, ImageDraw, ImageFont
import cv2
import numpy as np
# cv2读取图片，名称不能有汉字
img = cv2.imread('pic1.jpeg') 
# cv2和PIL中颜色的hex码的储存顺序不同
cv2img = cv2.cvtColor(img, cv2.COLOR_BGR2RGB) 
pilimg = Image.fromarray(cv2img)
# PIL图片上打印汉字
draw = ImageDraw.Draw(pilimg) # 图片上打印
#simsun 宋体
font = ImageFont.truetype("simsun.ttf", 40, encoding="utf-8") 
#位置，文字，颜色==红色，字体引入
draw.text((20, 20), "你好", (255, 0, 0), font=font) 
# PIL图片转cv2 图片
cv2charimg = cv2.cvtColor(np.array(pilimg), cv2.COLOR_RGB2BGR)
cv2.imshow("img", cv2charimg)
cv2.waitKey (0)
cv2.destroyAllWindows()

存在的缺点：cv2->pil 中 Image.fromarray(img)存在耗时4~5ms

2.方法二：opencv重新编译带freetype

编译过程略。

import cv2
import numpy as np
# 创建一个黑色的图像
img = np.zeros((300, 500, 3), dtype=np.uint8)
# 中文文本
text = '你好，OpenCV！'
# 设置字体相关参数
font_path = 'path/to/your/chinese/font.ttf' # 替换为你的中文字体文件路径
font_size = 24
font_color = (255, 255, 255)
thickness = 2
# 使用 truetype 字体加载中文字体
font = cv2.freetype.createFreeType2()
font.loadFontData(font_path)
# 在图像上放置中文文本
position = (50, 150)
font.putText(img, text, position, font_size, font_color, thickness=thickness)
# 显示图像
cv2.imshow('Image with Chinese Text', img)
cv2.waitKey(0)
cv2.destroyAllWindows()

缺点：编译过程复杂繁琐，容易报一些列的错误，编译时确保已安装第三方库freetype和harfbuzz，并且配置编译参数时需打开freetype。

3.方法三：使用freetype-py

pip install freetype-py

ft.py

import numpy as np
import freetype
import copy
import pdb
import time
 
class PutChineseText(object):
 def __init__(self, ttf, text_size):
 self._face = freetype.Face(ttf)
 hscale = 1.0
 self.matrix = freetype.Matrix(int(hscale)*0x10000, int(0.2*0x10000),int(0.0*0x10000), int(1.1*0x10000))
 self.cur_pen = freetype.Vector()
 self.pen_translate = freetype.Vector()
 self._face.set_transform(self.matrix, self.pen_translate)
 self._face.set_char_size(text_size * 64)
 metrics = self._face.size
 ascender = metrics.ascender/64.0
 
 #descender = metrics.descender/64.0
 #height = metrics.height/64.0
 #linegap = height - ascender + descender
 self.ypos = int(ascender)
 self.pen = freetype.Vector()
 
 def draw_text(self, image, pos, text, text_color):
 '''
 draw chinese(or not) text with ttf
 :param image: image(numpy.ndarray) to draw text
 :param pos: where to draw text
 :param text: the context, for chinese should be unicode type
 :param text_size: text size
 :param text_color:text color
 :return: image
 '''
 
 
 # if not isinstance(text, unicode):
 # text = text.decode('utf-8')
 img = self.draw_string(image, pos[0], pos[1]+self.ypos, text, text_color)
 return img
 
 def draw_string(self, img, x_pos, y_pos, text, color):
 '''
 draw string
 :param x_pos: text x-postion on img
 :param y_pos: text y-postion on img
 :param text: text (unicode)
 :param color: text color
 :return: image
 '''
 prev_char = 0
 
 self.pen.x = x_pos 6
 y_pos = pen.y >> 6
 cols = bitmap.width
 rows = bitmap.rows
 
 glyph_pixels = bitmap.buffer
 
 for row in range(rows):
 for col in range(cols):
 if glyph_pixels[row*cols + col] != 0:
 img[y_pos + row][x_pos + col][0] = color[0]
 img[y_pos + row][x_pos + col][1] = color[1]
 img[y_pos + row][x_pos + col][2] = color[2]
 
 
if __name__ == '__main__':
 # just for test
 import cv2
 
 line = '你好'
 img = np.zeros([300,300,3])
 
 color_ = (0,255,0) # Green
 pos = (40, 40)
 text_size = 24
 
 ft = PutChineseText('font/simsun.ttc',text_size=20)
 t1 = time.time()
 image = ft.draw_text(img, pos, line, color_)
 print(f'draw load . ({time.time() - t1:.3f}s)')
 
 cv2.imshow('ss', image)
 cv2.waitKey(0)

缺点：每个字符耗时在0.3~1ms左右，耗时略大。

4.方法四：使用OpenCV5.0

4.1 编译opencv5.x版本

编译过程较复杂，不推荐。

4.2 使用rolling版本

卸载原先安装的opencv

pip uninstall opencv-python
pip uninstall opencv-contrib-python

安装rolling版本

pip install opencv-python-rolling
pip install opencv-contrib-python-rolling

安装完毕后，cv2.putText即可支持中文字符。

缺点：5.0版本暂未正式发布，可能存在不稳定情况

优点：耗时几乎没有