Pillow库的使用+图片转字符串

最新推荐文章于 2025-02-18 17:20:44 发布

Zach_z

最新推荐文章于 2025-02-18 17:20:44 发布

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分类专栏： python 文章标签： python 图像处理 pillow 图片转字符串

本文链接：https://blog.youkuaiyun.com/Zach_z/article/details/77394523

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13 篇文章

订阅专栏

一、Pillow

PIL(Python Imaging Library)是一个 Python 图像处理库,Pillow 是一个对 PIL 友好的分支

1. 安装Pillow

pip install Pillow

如果下载失败或者超时，Linux下用国内镜像下载

pip  install --index https://pypi.mirrors.ustc.edu.cn/simple/ pillow

2. Image类

PIL中最重要的是Image类,可以通过几种方法实例化:从文件中加载图像，处理其他图像得到，或者直接创建一个图像

2.1从文件中加载图像

使用open()函数加载图像，通过使用示例属性查看文件内容

from PIL import Image
im=Image.open("./2+2.jpg")
print(im.format, im.size, im.mode)

运行结果：

$ python test1.py
('JPEG', (954, 960), 'RGB')

format：这个属性标识了图像来源。如果图像不是从文件读取它的值就是None

size：属性是一个二元tuple，包含width和height（宽度和高度，单位都是px）

mode 属性定义了图像bands的数量和名称，以及像素类型和深度。常见的modes 有 “L” (luminance) 表示灰度图像, “RGB” 表示真彩色图像, and “CMYK” 表示出版图像

如果文件打开错误，返回 IOError 错误

2.2对图像进行处理

2.2.1图像的裁剪

用PIL.Image.Image.crop方法获取图像一个子矩形区域

box = (0,0,500,500)
region = im.crop(box)

2.2.2图像的旋转

rotate(x): x需要顺时针旋转的角度

region = region.rotate(90) //顺时针旋转90°

在Pillow中，对于一些常见的旋转作了专门的定义：

region = region.transpose(Image.FLIP_LEFT_RIGHT)
region = region.transpose(Image.FLIP_TOP_BOTTOM)
region = region.transpose(Image.ROTATE_90)
region = region.transpose(Image.ROTATE_180)
region = region.transpose(Image.ROTATE_270)

2.2.3图像的粘贴合并

paste(now,old),粘贴矩形选区时候必须保持尺寸一致

im.paste(region, box)

2.2.4图像大小变换

resize((x,y))

im=im.resize((600,600))

2.2.5 颜色变换

convert(“L”) 彩色转化为黑白

convert(“CMYK”) 转化为出版彩色

im = im.convert("L")
im = im.convert("CMYK")

2.3 保存图片

save方法即可保存图片

综合上面图像处理方法的代码:

from PIL import Image
im=Image.open("./2+2.jpg") #打开图片
print(im.format, im.size, im.mode) #打印相关属性
box = (0,0,500,500) 
region = im.crop(box) #选取了一块500*500px的矩形选区
region = region.rotate(90) #选区顺时针旋转90°
im.paste(region, box) #粘贴到原图位置
im=im.resize((600,600)) #原图图片大小变为600*600
im = im.convert("L") #图片转化为灰色
print(im.format, im.size, im.mode) #打印相关属性
im.save("./2+2_new.jpg") #保存图片

运行结果

$ python test1.py
('JPEG', (954, 960), 'RGB')
(None, (600, 600), 'L')

之前图片:

这里写图片描述
之后图片:

这里写图片描述

二、图片转字符串

1.原理

用一个字符表现一种颜色，将彩色图(RGB)转换成灰度图，用著名心理学公式

Gray = R*0.299 + G*0.587 + B*0.114

灰度值:指黑白图像中点的颜色深度，范围一般从0到255，白色为255，黑色为0.

创建一个不重复的字符列表，灰度值小（暗）的用列表开头的符号，灰度值大（亮）的用列表末尾的符号

2.实现

#*- coding:utf-8 -*-

from PIL import Image
import argparse

#命令行输入参数处理
parser = argparse.ArgumentParser()

parser.add_argument('file')     #输入文件
parser.add_argument('-o', '--output')   #输出文件
parser.add_argument('--width', type = int, default = 80) #输出字符画宽
parser.add_argument('--height', type = int, default = 80) #输出字符画高

#获取参数
args = parser.parse_args()

IMG = args.file
WIDTH = args.width
HEIGHT = args.height
OUTPUT = args.output

ascii_char = list("$@B%8&WM#*oahkbdpqwmZO0QLCJUYXzcvunxrjft/\|()1{}[]?-_+~<>i!lI;:,\"^`'. ")

# 将256灰度映射到70个字符上
def get_char(r,g,b,alpha = 256):
    if alpha == 0:
        return ' '
    length = len(ascii_char)
    gray = int(0.299 * r + 0.587 * g + 0.114 * b)
    unit = (256.0 + 1)/length
    return ascii_char[int(gray/unit)]

if __name__ == '__main__':

    im = Image.open(IMG)
    im = im.resize((WIDTH,HEIGHT), Image.NEAREST)

    txt = ""

    for i in range(HEIGHT):
        for j in range(WIDTH):
            txt += get_char(*im.getpixel((j,i)))
        txt += '\n'

    print txt

    #字符画输出到文件
    if OUTPUT:
        with open(OUTPUT,'w') as f:
            f.write(txt)
    else:
        with open("output.txt",'w') as f:
            f.write(txt)

运行结果:

$ python pic_to_str.py 2+2.jpg -o 2+2.txt
$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$
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