python3.6环境下安装freetype库和基本使用方法(推荐)

FreeType库是一个完全免费（开源）的、高质量的且可移植的字体引擎，它提供统一的接口来访问多种字体格式文件，包括TrueType, OpenType, Type1, CID, CFF, Windows FON/FNT, X11 PCF等。在做图像展示的时候，可以写入中文文字，效果还是很好。

在之前安装库时基本都是直接切换到python3.6环境下直接pip install XXX，在安装freetype直接pip install freetype不可以了，查了半天又是编译又是官网下载的，太麻烦，不推荐。

（1）正确的安装方法：
注意：一定要加上 -py

pip install freetype-py

（2）常用调用方法

已经封装好了一个文件，可直接保存后调用。

import freetype
import copy


class put_chinese_text(object):
 def __init__(self, ttf):
  self._face = freetype.Face(ttf)

 def draw_text(self, image, pos, text, text_size, 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
  '''
  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
  ypos = int(ascender)

  text = text
  img = self.draw_string(image, pos[0], pos[1] + 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
  pen = freetype.Vector()
  pen.x = x_pos << 6 # div 64
  pen.y = y_pos << 6

  hscale = 1.0
  matrix = freetype.Matrix(int(hscale) * 0x10000, int(0.2 * 0x10000), \
         int(0.0 * 0x10000), int(1.1 * 0x10000))
  cur_pen = freetype.Vector()
  pen_translate = freetype.Vector()

  image = copy.deepcopy(img)
  for cur_char in text:
   self._face.set_transform(matrix, pen_translate)

   self._face.load_char(cur_char)
   kerning = self._face.get_kerning(prev_char, cur_char)
   pen.x += kerning.x
   slot = self._face.glyph
   bitmap = slot.bitmap

   cur_pen.x = pen.x
   cur_pen.y = pen.y - slot.bitmap_top * 64
   self.draw_ft_bitmap(image, bitmap, cur_pen, color)

   pen.x += slot.advance.x
   prev_char = cur_char

  return image

 def draw_ft_bitmap(self, img, bitmap, pen, color):
  '''
  draw each char
  :param bitmap: bitmap
  :param pen: pen
  :param color: pen color e.g.(0,0,255) - red
  :return:  image
  '''
  x_pos = pen.x >> 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:
     try:
      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]
     except:
      continue


if __name__ == '__main__':
 # just for test
 import cv2

 line = '毛不易'
 img = cv2.imread('./aa.jpg')

 color_ = (0, 255, 0) # Green
 pos = (3, 3)
 text_size = 24
 ft = put_chinese_text('yahei.ttf')
 image = ft.draw_text(img, pos, line, text_size, color_)

 cv2.imshow('ss', image)
 cv2.waitKey(0)

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