将TrueType字体加载到OpenCV

Question

我们可以加载自定义的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字体的一个子集。

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 
}; 

如果您想使用自定义字体，您可以尝试使用PIL.ImageFont。

一个基本的例子这里介绍：

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)