cv2.putText(img, text, org, fontFace,fontScale, color[, thickness[, lineType[, bottomLeftOrigin]]])

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，数值表示线占有直径像素个数