cv2.putText(img, str(i), (123,456)), font, 2, (0,255,0), 3)

各参数依次是：图片，添加的文字，左上角坐标，字体，字体大小，颜色，字体粗细

其中字体可以选择

FONT_HERSHEY_SIMPLEX

Python: cv.FONT_HERSHEY_SIMPLEX

normal size sans-serif font

FONT_HERSHEY_PLAIN

Python: cv.FONT_HERSHEY_PLAIN

small size sans-serif font

FONT_HERSHEY_DUPLEX

Python: cv.FONT_HERSHEY_DUPLEX

normal size sans-serif font (more complex than FONT_HERSHEY_SIMPLEX)

FONT_HERSHEY_COMPLEX

Python: cv.FONT_HERSHEY_COMPLEX

normal size serif font

FONT_HERSHEY_TRIPLEX

Python: cv.FONT_HERSHEY_TRIPLEX

normal size serif font (more complex than FONT_HERSHEY_COMPLEX)

FONT_HERSHEY_COMPLEX_SMALL

Python: cv.FONT_HERSHEY_COMPLEX_SMALL

smaller version of FONT_HERSHEY_COMPLEX

FONT_HERSHEY_SCRIPT_SIMPLEX

Python: cv.FONT_HERSHEY_SCRIPT_SIMPLEX

hand-writing style font

FONT_HERSHEY_SCRIPT_COMPLEX

Python: cv.FONT_HERSHEY_SCRIPT_COMPLEX

more complex variant of FONT_HERSHEY_SCRIPT_SIMPLEX

FONT_ITALIC

Python: cv.FONT_ITALIC

flag for italic font

字体大小，数值越大，字体越大

字体粗细，越大越粗，数值表示描绘的线条占有的直径像素个数

Python:

img =cv.putText(img, text, org, fontFace,fontScale,color[, thickness[, lineType[, bottomLeftOrigin]]])