Example explanation of Python generating verification code

Verification code is often used in web development. In order to prevent robot registration or malicious login and query, its role cannot be underestimated

But verification code is not actually a function that can be done. It needs to generate pictures and watermarks. In fact, each Each language has related functions to generate image and text watermarks. Including php, which I am familiar with, haha, today I will mainly share how to use python to generate verification codes.

Python mainly uses the following modules to generate verification codes: Image, ImageDraw, ImageFont, ImageFilter and random number generation module Random.

The code is as follows:

#!/usr/bin/env python
#coding=utf-8
import random
import Image, ImageDraw, ImageFont, ImageFilter
  
_letter_cases = "abcdefghjkmnpqrstuvwxy" # 小写字母，去除可能干扰的i，l，o，z
_upper_cases = _letter_cases.upper() # 大写字母
_numbers = ''.join(map(str, range(3, 10))) # 数字
init_chars = ''.join((_letter_cases, _upper_cases, _numbers))
fontType="/usr/share/fonts/truetype/freefont/FreeSans.ttf"
  
def create_validate_code(size=(120, 30),
                             chars=init_chars,
                             img_type="GIF",
                             mode="RGB",
                             bg_color=(255, 255, 255),
                             fg_color=(0, 0, 255),
                             font_size=18,
                             font_type=fontType,
                             length=4,
                             draw_lines=True,
                             n_line=(1, 2),
                             draw_points=True,
                             point_chance = 2):
  '''
  @todo: 生成验证码图片
  @param size: 图片的大小，格式（宽，高），默认为(120, 30)
  @param chars: 允许的字符集合，格式字符串
  @param img_type: 图片保存的格式，默认为GIF，可选的为GIF，JPEG，TIFF，PNG
  @param mode: 图片模式，默认为RGB
  @param bg_color: 背景颜色，默认为白色
  @param fg_color: 前景色，验证码字符颜色，默认为蓝色#0000FF
  @param font_size: 验证码字体大小
  @param font_type: 验证码字体，默认为 ae_AlArabiya.ttf
  @param length: 验证码字符个数
  @param draw_lines: 是否划干扰线
  @param n_lines: 干扰线的条数范围，格式元组，默认为(1, 2)，只有draw_lines为True时有效
  @param draw_points: 是否画干扰点
  @param point_chance: 干扰点出现的概率，大小范围[0, 100]
  @return: [0]: PIL Image实例
  @return: [1]: 验证码图片中的字符串
  '''
  
  width, height = size # 宽， 高
  img = Image.new(mode, size, bg_color) # 创建图形
  draw = ImageDraw.Draw(img) # 创建画笔
  if draw_lines:
    create_lines(draw,n_line,width,height)
  if draw_points:
    create_points(draw,point_chance,width,height)
  strs = create_strs(draw,chars,length,font_type, font_size,width,height,fg_color)
  
  # 图形扭曲参数
  params = [1 - float(random.randint(1, 2)) / 100,
            0,
            0,
            0,
            1 - float(random.randint(1, 10)) / 100,
            float(random.randint(1, 2)) / 500,
            0.001,
            float(random.randint(1, 2)) / 500
            ]
  img = img.transform(size, Image.PERSPECTIVE, params) # 创建扭曲
  
  img = img.filter(ImageFilter.EDGE_ENHANCE_MORE) # 滤镜，边界加强（阈值更大）
  
  return img, strs
  
  
def create_lines(draw,n_line,width,height):
  '''绘制干扰线'''
  line_num = random.randint(n_line[0],n_line[1]) # 干扰线条数
  for i in range(line_num):
    # 起始点
    begin = (random.randint(0, width), random.randint(0, height))
    #结束点
    end = (random.randint(0, width), random.randint(0, height))
    draw.line([begin, end], fill=(0, 0, 0))
  
def create_points(draw,point_chance,width,height):
  '''绘制干扰点'''
  chance = min(100, max(0, int(point_chance))) # 大小限制在[0, 100]
   
  for w in xrange(width):
    for h in xrange(height):
      tmp = random.randint(0, 100)
      if tmp > 100 - chance:
        draw.point((w, h), fill=(0, 0, 0))
  
def create_strs(draw,chars,length,font_type, font_size,width,height,fg_color):
  '''绘制验证码字符'''
  '''生成给定长度的字符串，返回列表格式'''
  c_chars = random.sample(chars, length)
  strs = ' %s ' % ' '.join(c_chars) # 每个字符前后以空格隔开
   
  font = ImageFont.truetype(font_type, font_size)
  font_width, font_height = font.getsize(strs)
  
  draw.text(((width - font_width) / 3, (height - font_height) / 3),strs, font=font, fill=fg_color)
   
  return ''.join(c_chars)
  
  
if __name__ == "__main__":
    code_img = create_validate_code()
    code_img[0].save("validate.gif", "GIF")
    print code_img[1]