Creating a complex PDF file according to precise instructions and meticulous specifications

Question

[Sorry for my bad English]

We are developing an application that manages information about public transportation. The application should generate posters for signage at bus stops.

The posters should conform to detailed and strict regulatory rules, in every detail. Typography, colors, tables, lines, symbols, embedded images and much more.

We need to produce the poster as a PDF file, which will be sent for printing.

Our question: How to produce this file in a reliable and efficient way?

Do we should to create an HTML+CSS file, then use a library that converts HTML to PDF? Can we trust the library to convert the HTML completely accurately?

Or we should to use libraries that generate PDF directly like iText. Do they support creating a complex PDF according to exact specifications?

And what is the most suitable environment to do it? Our first priority is do.net core, but if there is no choice, we will also consider using python or node.

And a final question, to which field of knowledge does this belong? What skills are needed to perform the task? We want to publish a tender for this task, and don't know what to ask for.

Answer 1

disclaimer: I am the author of borb , the library used in this answer

In general, there are two kinds of PDF libraries.

• high level libraries: These libraries allow you to easily add content (images, text, tables, lists, etc) without having to specify too much. It's easier for you (the user) but you're giving up precise control.
• low level libraries: These libraries bring you (the user) down to the nitty gritty level of the PDF. You can manipulate content and place it at exact positions. You can define a color space (ensuring the color can be calibrated), etc. This also means you give up comfort. You can not (easily) split text, automatically flow content blocks, etc

borb allows you to do both. You can place content at exact coordinates, you can specify your own fonts, you can set colors using RGB, HSV, etc

You can also use a PageLayout which will take over most of the content-placement.

This is an example using absolute positioning:

from borb.pdf import Document
from borb.pdf import Page
from borb.pdf import Paragraph
from borb.pdf import PDF
from borb.pdf.canvas.geometry.rectangle import Rectangle

from decimal import Decimal


def main():
    # create Document
    doc: Document = Document()

    # create Page
    page: Page = Page()

    # add Page to Document
    doc.add_page(page)

    # define layout rectangle
    # fmt: off
    r: Rectangle = Rectangle(
        Decimal(59),                # x: 0 + page_margin
        Decimal(848 - 84 - 100),    # y: page_height - page_margin - height_of_textbox
        Decimal(595 - 59 * 2),      # width: page_width - 2 * page_margin
        Decimal(100),               # height
    )
    # fmt: on

    # the next line of code uses absolute positioning
    Paragraph("Hello World!").paint(page, r)

    # store
    with open("output.pdf", "wb") as pdf_file_handle:
        PDF.dumps(pdf_file_handle, doc)


if __name__ == "__main__":
    main()

And this is that same example using a PageLayout

from borb.pdf import Document
from borb.pdf import Page
from borb.pdf import PageLayout
from borb.pdf import SingleColumnLayout
from borb.pdf import Paragraph
from borb.pdf import PDF


def main():
    # create Document
    doc: Document = Document()

    # create Page
    page: Page = Page()

    # add Page to Document
    doc.add_page(page)

    # set a PageLayout
    layout: PageLayout = SingleColumnLayout(page)

    # add a Paragraph
    layout.add(Paragraph("Hello World!"))

    # store
    with open("output.pdf", "wb") as pdf_file_handle:
        PDF.dumps(pdf_file_handle, doc)


if __name__ == "__main__":
    main()