pillow实例 | 生成随机验证码

1 PIL(Python Image Library)

PIL是Python进行基本图片处理的package，囊括了诸如图片的剪裁、缩放、写入文字等功能。现在，我便以生成随机验证码为例，讲述PIL的基本用法。

PIL库似乎已经被人抛弃，就为更新，上次使用时竟然不能用show()直接将图片，在系统默认的图片管理器中打开。好在pillow，一个PIL的方言，将PIL继续维护了下去。

生成验证码一般需要对写入的文字进行旋转、扭曲、变色等一系列操作，才能避免计算机算法的识别。

因此定义一个生成验证码的类是一个不错的选择，旋转、扭曲、变色就作为这个类的一系列方法。

2 初始化Captcha类

Captcha是Completely Automated Public Turing Test to Tell Computers and Humans Apart (全自动区分计算机和人类的图灵测试)的简称，是世界上最为著名的验证码项目，后来被google受够，现在它们开始用图片以外的其他方式来区分人与计算机

初始化需要设置验证码图片的大小、以及字体的大小，默认已选择了比较合适的值。

需要用到Draw子包的new方法新建一张图片，要给定mode、size和color。这就像是现实画画中的幕布。

mode与不同的图片表示格式有关，

彩色图片是可以通过红R、绿G、蓝B三原色合成而来，存储在计算机里的便是3个矩阵，这种最常见的模式叫做'RGB'；

黑白图片则只需要一层，用'1'表示；

在计算机屏幕显示的彩色图片在三原色的基础上，进而出现一个透明层，表示能够透过多少下一层图片，这种模式叫做'RGBA'，A代指alpha。

from PIL import Image

class Captcha(object):
    def __init__(self,size=(100,40),fontSize=30):
        self.font = ImageFont.truetype('C:\Windows\Fonts\Arial.ttf',fontSize)
        self.size = size
        self.image = Image.new('RGBA',self.size,(255,)*4)
        self.texts = self.randNum(5)

ImageFont包用于处理字体，需要具体给定使用字体的路径以及字体的大小，Windows系统下字都在C:\Windows\Fonts\路径下。

3 生成随机的数字及颜色

随机数字

使用random包的randint(start,end)方法，随机产生0~9中的一个数字，需要注意的是包含start和end

    def randNum(self,bits):
        return ''.join(str(random.randint(0,9)) for i in range(bits))

随机颜色

颜色一般用8位表示，十进制下便是0~255的一个整数，随机生成一个三元组即可

    def randColor(self):
        self.fontColor = (random.randint(0,250),random.randint(0,250),random.randint(0,250))

这都非常简单

4 写入文字

写入文字需要用到ImageDraw包

    def write(self,text,x):
        draw = ImageDraw.Draw(self.image)
        draw.text((x,4),text,fill=self.fontColor,font=self.font)

text方法需要指定，写入文字的位置，以左上角为原点，当然以像素为单位；写入的文字；写入文字的颜色；最后说字体

5 旋转文字

旋转一般不是直接旋转文字，而是旋转幕布，在这里需要随机旋转一个角度。

旋转幕布会产生一个问题，旋转后边边角角会伸到画板的外面，而最终我们需要一个方方正正的验证码图片。

伸到画板外面的幕布需要剪裁掉，因为旋转空余的地方又需要补上。

Image.composite(img1,img2,img1)就可以解决这个问题，它会把img1透明/空白的地方，用img2补上。在这里应该是纯白的背景。

    def rotate(self):
        rot = self.image.rotate(random.randint(-10,10),expand=0) #默认为0，表示剪裁掉伸到画板外面的部分
        fff = Image.new('RGBA',rot.size,(255,)*4)
        self.image = Image.composite(rot,fff,rot)

6 形成验证码

有了上面的方法作铺垫，以一定的间隔，写上几个数字，就得到验证码了

    def writeNum(self):
        x = 10
        xplus = 15
        for text in self.texts:
            self.randColor()
            self.write(text, x)
            self.rotate()
            x += xplus
        return self.texts

此方法会返回验证码的文字，这样计算机才能判断人是否输入正确。不像上面的几个方法，这个方法是面向用户的。

最终的效果是这样子的aaarticlea/jpeg;base64,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" alt="" /> aaarticlea/jpeg;base64,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" alt="" />

附：完整的代码

class Captcha(object):
    def __init__(self,size=(100,40),fontSize=30):
        self.font = ImageFont.truetype('C:\Windows\Fonts\Arial.ttf',fontSize)
        self.size = size
        self.image = Image.new('RGBA',self.size,(255,)*4)
        self.texts = self.randNum(5)

    def rotate(self):
        rot = self.image.rotate(random.randint(-10,10),expand=0)
        fff = Image.new('RGBA',rot.size,(255,)*4)
        self.image = Image.composite(rot,fff,rot)

    def randColor(self):
        self.fontColor = (random.randint(0,250),random.randint(0,250),random.randint(0,250))

    def randNum(self,bits):
        return ''.join(str(random.randint(0,9)) for i in range(bits))

    def write(self,text,x):
        draw = ImageDraw.Draw(self.image)
        draw.text((x,4),text,fill=self.fontColor,font=self.font)

    def writeNum(self):
        x = 10
        xplus = 15
        for text in self.texts:
            self.randColor()
            self.write(text, x)
            self.rotate()
            x += xplus
        return self.texts

    def save(self):
        self.image.save('captcha.jpg')

img = Captcha()
num = img.writeNum()
#img.image.show()
#img.save()