OCR-PIL.Image與Base64 String的互相轉換

1. 基本環境

• py2: python2.7.13
• py3: python3.6.2
• PIL: pip(2/3) install pillow, PIL庫已不再維護，而pillow是PIL的一個分支，如今已超越PIL

2. Convert PIL.Image to Base64 String

• py2 ：先使用CStringIO.StringIO把圖片內容轉爲二進制流，再進行base64編碼

# -*- coding: utf-8 -*-

import base64
from cStringIO import StringIO

# pip2 install pillow
from PIL import Image


def image_to_base64(image_path):
    img = Image.open(image_path)
    output_buffer = StringIO()
    img.save(output_buffer, format='JPEG')
    binary_data = output_buffer.getvalue()
    base64_data = base64.b64encode(binary_data)
    return base64_data

• py3：python3中沒有cStringIO，對應的是io，但卻不能使用io.StringIO來處理圖片，它用來處理文本的IO操作，處理圖片的應該是io.BytesIO

import base64
from io import BytesIO

# pip3 install pillow
from PIL import Image

# 若img.save()報錯 cannot write mode RGBA as JPEG
# 則img = Image.open(image_path).convert('RGB')
def image_to_base64(image_path):
    img = Image.open(image_path)
    output_buffer = BytesIO()
    img.save(output_buffer, format='JPEG')
    byte_data = output_buffer.getvalue()
    base64_str = base64.b64encode(byte_data)
    return base64_str

3. Convert Base64 String to PIL.Image

• py2:

# -*- coding: utf-8 -*-

import re
import base64
from cStringIO import StringIO

from PIL import Image


def base64_to_image(base64_str, image_path=None):
    base64_data = re.sub('^data:image/.+;base64,', '', base64_str)
    binary_data = base64.b64decode(base64_data)
    img_data = StringIO(binary_data)
    img = Image.open(img_data)
    if image_path:
        img.save(image_path)
    return img

• py3:

import re
import base64
from io import BytesIO

from PIL import Image


def base64_to_image(base64_str, image_path=None):
    base64_data = re.sub('^data:image/.+;base64,', '', base64_str)
    byte_data = base64.b64decode(base64_data)
    image_data = BytesIO(byte_data)
    img = Image.open(image_data)
    if image_path:
        img.save(image_path)
    return img

4. 參考網址

[1] https://stackoverflow.com/questions/16065694/is-it-possible-to-create-encodeb64-from-image-object

[2] https://stackoverflow.com/questions/31826335/how-to-convert-pil-image-image-object-to-base64-string

[3] https://stackoverflow.com/questions/26070547/decoding-base64-from-post-to-use-in-pil