将TrueType字体加载到OpenCV

Question

我们可以加载自定义TrueType字体并将其与cv2.putText函数一起使用吗？

font = cv2.FONT_HERSHEY_SIMPLEX
cv2.putText(img,'OpenCV',(10,500), font, 4,(255,255,255),2,cv2.LINE_AA)

Answer 1

在OpenCV中，只支持Hershey字体的一部分。

在opencv2/core.hpp中，您可以找到此枚举HersheyFonts。

//! Only a subset of Hershey fonts
enum HersheyFonts {
    FONT_HERSHEY_SIMPLEX        = 0, //!< normal size sans-serif font
    FONT_HERSHEY_PLAIN          = 1, //!< small size sans-serif font
    FONT_HERSHEY_DUPLEX         = 2, //!< normal size sans-serif font (more complex than FONT_HERSHEY_SIMPLEX)
    FONT_HERSHEY_COMPLEX        = 3, //!< normal size serif font
    FONT_HERSHEY_TRIPLEX        = 4, //!< normal size serif font (more complex than FONT_HERSHEY_COMPLEX)
    FONT_HERSHEY_COMPLEX_SMALL  = 5, //!< smaller version of FONT_HERSHEY_COMPLEX
    FONT_HERSHEY_SCRIPT_SIMPLEX = 6, //!< hand-writing style font
    FONT_HERSHEY_SCRIPT_COMPLEX = 7, //!< more complex variant of FONT_HERSHEY_SCRIPT_SIMPLEX
    FONT_ITALIC                 = 16 //!< flag for italic font
};

如果要使用自定义字体，可以尝试PIL.ImageFont。

此处提供了一个基本示例：

import numpy as np
from PIL import ImageFont, ImageDraw, Image
import cv2
import time

## Make canvas and set the color
img = np.zeros((200,400,3),np.uint8)
b,g,r,a = 0,255,0,0

## Use cv2.FONT_HERSHEY_XXX to write English.
text = time.strftime("%Y/%m/%d %H:%M:%S %Z", time.localtime()) 
cv2.putText(img,  text, (50,50), cv2.FONT_HERSHEY_SIMPLEX, 0.7, (b,g,r), 1, cv2.LINE_AA)

## Use simsum.ttc to write Chinese.
fontpath = "./simsun.ttc"     
font = ImageFont.truetype(fontpath, 32)
img_pil = Image.fromarray(img)
draw = ImageDraw.Draw(img_pil)
draw.text((50, 100),  "国庆节/中秋节 快乐!", font = font, fill = (b, g, r, a))
img = np.array(img_pil)

## Display 
cv2.imshow("res", img);cv2.waitKey();cv2.destroyAllWindows()
cv2.imwrite("res.png", img)

Answer 2

对于新查看者，OpenCV自OpenCV 3.0.0起通过FreeType2类支持自定义字体。参见一些不错的示例代码：https://docs.opencv.org/4.1.1/d9/dfa/classcv_1_1freetype_1_1FreeType2.html

Answer 3

您还可以使用https://github.com/bunkahle/PILasOPENCV处的库PILasOPENCV将truetype字体与Python OpenCV结合使用。不需要PIL或枕头。该模块取决于库freetype-py。字体将这样导入：

iris %>% 
    group_by(Species) %>% 
    summarise(out = list(SlowFunction(Sepal.Length))) %>%
    unnest
# A tibble: 3 x 3
#  Species     mean    sd
#  <fct>      <dbl> <dbl>
#1 setosa      5.01 0.352
#2 versicolor  5.94 0.516
#3 virginica   6.59 0.636

该库是常用PIL函数的包装，但在内部与OpenCV一起使用。