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I'm trying to develop a simple app in Python Flet for displaying each page of a Pdf file. The code imports the pypdf library for PDF management. The UI consists of a button for loading the first page of the PDF and for skipping to the next page, and of a Flet container whose content is a Flet image. Flet image takes a Base64 encoded string which should correspond, in turn, to every single page of the PDF.

import flet as ft
import pypdf

def main(page: ft.Page):
    def btn_Click(e):
        cont.content = ft.Image(src_base64 = reader.pages[0],
            fit=ft.ImageFit.FILL,
            )
        page.update()
        
        if btn.data < len(reader.pages):
            btn.data +=1
            
    reader = pypdf.PdfReader('Your Pdf filename.pdf')

    cont = ft.Container(height = 0.8*page.height,
        width = 0.4 * page.width,
        border=ft.border.all(3, ft.colors.RED),)

    btn = ft.IconButton(
        icon=ft.icons.UPLOAD_FILE,
        on_click=btn_Click,
        icon_size=35,
        data=0,)    

    page.add(ft.Column([cont, btn], horizontal_alignment="center"))
    page.horizontal_alignment = "center"
    page.scroll = ft.ScrollMode.AUTO
    page.update()

ft.app(target=main, assets_dir="assets")

Once the button is clicked, I get this error:

Error decoding base64: FormatException: Invalid character (at character 1)
{'/Contents': [IndirectObject(2286, 0, 1969514531216), IndirectObject(2287,...
^

Searching in the web, I found that this exception already happened with Flutter, from which the framework Flet is derived. See this link, this and this. It was suggested to apply this conversion:

base64.decode(sourceContent.replaceAll(RegExp(r'\s+'), ''))

I don't know how to apply it to the my variable reader. Or, alternatevely, if pypdf contains a method for making this conversion.

I'm trying to develop a simple app in Python Flet for displaying each page of a Pdf file. The code imports the pypdf library for PDF management. The UI consists of a button for loading the first page of the PDF and for skipping to the next page, and of a Flet container whose content is a Flet image. Flet image takes a Base64 encoded string which should correspond, in turn, to every single page of the PDF.

import flet as ft
import pypdf

def main(page: ft.Page):
    def btn_Click(e):
        cont.content = ft.Image(src_base64 = reader.pages[0],
            fit=ft.ImageFit.FILL,
            )
        page.update()
        
        if btn.data < len(reader.pages):
            btn.data +=1
            
    reader = pypdf.PdfReader('Your Pdf filename.pdf')

    cont = ft.Container(height = 0.8*page.height,
        width = 0.4 * page.width,
        border=ft.border.all(3, ft.colors.RED),)

    btn = ft.IconButton(
        icon=ft.icons.UPLOAD_FILE,
        on_click=btn_Click,
        icon_size=35,
        data=0,)    

    page.add(ft.Column([cont, btn], horizontal_alignment="center"))
    page.horizontal_alignment = "center"
    page.scroll = ft.ScrollMode.AUTO
    page.update()

ft.app(target=main, assets_dir="assets")

Once the button is clicked, I get this error:

Error decoding base64: FormatException: Invalid character (at character 1)
{'/Contents': [IndirectObject(2286, 0, 1969514531216), IndirectObject(2287,...
^

Searching in the web, I found that this exception already happened with Flutter, from which the framework Flet is derived. See this link, this and this. It was suggested to apply this conversion:

base64.decode(sourceContent.replaceAll(RegExp(r'\s+'), ''))

I don't know how to apply it to the my variable reader. Or, alternatevely, if pypdf contains a method for making this conversion.

• python
• flutter
• dart
• pypdf
• flet

Share Improve this question Follow asked Nov 21, 2024 at 15:07 eljambaeljamba 37522 gold badges33 silver badges1616 bronze badges 1

• 2 pypdf has no rendering functionality and you could only export single-page PDF files as base64. It seems like you want to render the page content, thus you probably want to use another library (pdf2image based upon pdftocairo, PyMuPDF, Ghostscript or similar). – epR8GaYuh Commented Nov 22, 2024 at 20:07

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1 Answer 1

Sorted by: Reset to default 1

pypdf does not implement any rendering functionality, thus you cannot apply it to your use-case here. The output you get is the internal representation of the PDF page used by pypdf.

If you just want to display the PDF file inside the web browser, I would probably go with the pdf.js library which does all the rendering on the frontend side.

If you really need image-based output, there are lots of libraries/tools which you could use:

• pdf2image, which is based upon the poppler library
• (Py)MuPDF
• Ghostscript
• pypdfium2
• pyvips
• ...

An example for pdf2image to get the first page as JPG data could look like this:

import base64
from io import BytesIO

import pdf2image


images = pdf2image.convert_from_path('file.pdf', first_page=1, last_page=1, fmt='jpg', use_pdftocairo=True)
image = images[0]
image_buffer = BytesIO()
image.save(image_buffer, format='JPEG')
image_data = base64.b64encode(image_buffer.getvalue())

For further options, like the resolution to use for rendering etc., see the corresponding upstream documentation.

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