python 的 PDF 数据流

Question

上下文： 我的代码从一些 png 文档中获取一组坐标，然后在某些字段中执行一些编辑（它使用这些坐标在某些区域绘制矩形）。

我希望我的最终输出是一个 pdf 文件，每个经过编辑的图像作为页面。我可以毫无问题地使用 fpdf 包实现此目的。

但是，我打算将此 pdf 文件作为电子邮件（base64 编码）附件发送。有没有办法从 fpdf 输出中获取 base64 字符串？

最重要的是，我可以在 fpdf 图像方法中使用图像二进制字符串吗？

请参阅下面的 redact_pdf 方法（我在此处放置了一些注释以便更清楚）

代码：

class Redaction:
def __init__(self,png_image_list,df_coordinates):
    self.png_image_list = png_image_list
    self.df_coordinates = df_coordinates
    
def _redact_images(self):
    redacted_images_bin = []
    for page_num,page_data in enumerate(self.png_image_list):
        im_page = Image.open(io.BytesIO(page_data))
        draw = ImageDraw.Draw(im_page)
        df_filtered = self.df_coordinates[self.df_coordinates['page_number'] == page_num+1]
        for index, row in df_filtered.iterrows():
            x0 = row['x0'] * im_page.size[0]
            y0 = row['y0'] * im_page.size[1]
            x1 = row['x1'] * im_page.size[0]
            y1 = row['y1'] * im_page.size[1]
            x2 = row['x2'] * im_page.size[0]
            y2 = row['y2'] * im_page.size[1]
            x3 = row['x3'] * im_page.size[0]
            y3 = row['y3'] * im_page.size[1]
            coords = [x0,y0,x1,y1,x2,y2,x3,y3]
            draw.polygon(coords,outline='blue',fill='yellow')
        redacted_images_bin.append(im_page)
        
    return redacted_images_bin

def redacted_pdf(self):
    redacted_images = self._redact_images()
    pdf = FPDF()
    pdf.set_auto_page_break(0)
    for index,img_redacted in enumerate(redacted_images):
        img_redacted.save(f"image_{index}.png")
        pdf.add_page()
        pdf.image(f"image_{index}.png",w=210,h=297)
        os.remove(f"image_{index}.png") # I would like to avoid file handling!
    pdf.output("doc.pdf","F") # I would like to avoid file handling!
    #return pdf #this is what I want, to return the pdf as base64 or binary

Answer 1

在 documentation 中，我发现您可以使用

获取字符串形式的 PDF

pdf_string = pdf.output(dest='S')

所以你可以使用标准模块base64

import fpdf
import base64

pdf = fpdf.FPDF()

# ... add some elements ...

pdf_string = pdf.output(dest='S')
pdf_bytes  = pdf_string.encode('utf-8')

base64_bytes  = base64.b64encode(pdf_bytes)
base64_string = base64_bytes.decode('utf-8')

print(base64_string)

结果：

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

至于image()：它需要filename（或url）并且不能与string或io.BytesIO()一起使用。

最终你可能会得到source code，你可以尝试改变它。

GitHub 上什至有请求：Support for StringIO objects as images

编辑：

我发现有一个分支 fpdf2 可以在 image() 中使用 pillow.Image - 参见 fpdf2 Image

并且在 source code 中我发现 image() 也可以与 io.BytesIO()

一起使用

fpdf2 的示例代码（output() 给出 bytes 而不是 string）

import fpdf
import base64
from PIL import Image
import io

#print(fpdf.__version__)

pdf = fpdf.FPDF()

pdf.add_page()

pdf.image('lenna.png')

pdf.image('https://upload.wikimedia.org/wikipedia/en/7/7d/Lenna_%28test_image%29.png')

f = open('lenna.png', 'rb')
pdf.image(f)

f = Image.open('lenna.png')
pdf.image(f)

f = open('lenna.png', 'rb')
b = io.BytesIO()
b.write(f.read())
pdf.image(b)

# save in file
pdf.output('output.pdf')

# get as bytes
pdf_bytes = pdf.output()

#print(pdf_bytes)

base64_bytes  = base64.b64encode(pdf_bytes)
base64_string = base64_bytes.decode('utf-8')

print(base64_string)

维基百科：Lenna [image]

fpdf2

中的写作测试

import fpdf   

pdf = fpdf.FPDF()

pdf.add_page()
pdf.image('https://upload.wikimedia.org/wikipedia/en/7/7d/Lenna_%28test_image%29.png')

# --- test 1 ---

pdf.output('output-test-1.pdf')

# --- test 2 ---

pdf_bytes = pdf.output()

with open('output-test-2.pdf', 'wb') as f:  # it will close automatically
    f.write(pdf_bytes)

# --- test 2 ---

pdf_bytes = pdf.output()

f = open('output-test-3.pdf', 'wb')
f.write(pdf_bytes)
f.close()  # don't forget to close when you write

python 的 PDF 数据流

PDF data stream with python

python

python-3.x

pyfpdf