one-file-pdf

A minimalist Go PDF writer in 1982 lines. Draws text, images and shapes. Helps understand the PDF format. Used in production for reports.

Description

The main idea behind this project was: "How small can I make a PDF generator for it to still be useful for 80% of common PDF generation needs?"

The result is a single .go file with less than 1999 lines of code.

Programming language: Go

License: MIT License

Tags: GUI     Graphics     Writer     PDF     Minimalist     Printing    

README

one-file-pdf - A minimalist PDF generator in <2K lines and 1 file

The main idea behind this project was:
"How small can I make a PDF generator for it to still be useful for 80% of common PDF generation needs?"

The result is a single .go file with less than 1999 lines of code, about 400 of which are color and glyph-size constants, and ~350 are comments.

• It's easier to learn about the internals of the PDF format with a small, concise library.
• The current version of the file is indicated in the header (the timestamp).

Features:

• The essentials for generating PDF documents, sufficient for common business reports.
• Use all built-in PDF fonts: Courier, Helvetica, Symbol, Times, ZapfDingbats, and their variants
• Specify colo(u)rs by name (144 web colors), HTML codes (#RRGGBB) or RGB value
• Set columns for text (like tab stops on the page)
• Built-in grid option to help measurement and positioning
• Metadata properties: author, creator, keywords, subject and title
• Set the measurement units you want: mm, cm, inches, twips or points
• Draw lines with different thickness
• Filled or outline rectangles, circles and ellipses
• JPEG, GIF and transparent PNG images (filled with specified background color)
• Stream compression can be turned on or off (PDF files normally compress streams to reduce file size, but turning it off helps in debugging or learning about PDF commands)

Not Yet Supported:

• Unicode (requires font embedding)
• Font embedding
• PDF encryption
• Paths, curves and complex graphics

Installation:

    go get github.com/balacode/one-file-pdf

Naming Convention:

All types in are prefixed with PDF for public, and 'pdf' for private types. The only type you need to use is PDF, while PDFColorNames are left public for reference.

Hello World:

package main 

import (
    "fmt"
    "github.com/balacode/one-file-pdf"
)

func main() {
    fmt.Println(`Generating a "Hello World" PDF...`)

    // create a new PDF using 'A4' page size
    var pdf = pdf.NewPDF("A4")

    // set the measurement units to centimeters
    pdf.SetUnits("cm")

    // draw a grid to help us align stuff (just a guide, not necessary)
    pdf.DrawUnitGrid()

    // draw the word 'HELLO' in orange, using 100pt bold Helvetica font
    // - text is placed on top of, not below the Y-coordinate
    // - you can use method chaining
    pdf.SetFont("Helvetica-Bold", 100).
        SetXY(5, 5).
        SetColor("Orange").
        DrawText("HELLO")

    // draw the word 'WORLD' in blue-violet, using 100pt Helvetica font
    // note that here we use the colo(u)r hex code instead
    // of its name, using the CSS/HTML format: #RRGGBB
    pdf.SetXY(5, 9).
        SetColor("#8A2BE2").
        SetFont("Helvetica", 100).
        DrawText("WORLD!")

    // draw a flower icon using 300pt Zapf-Dingbats font
    pdf.SetX(7).SetY(17).
        SetColorRGB(255, 0, 0).
        SetFont("ZapfDingbats", 300).
        DrawText("a")

    // save the file:
    // if the file exists, it will be overwritten
    // if the file is in use, prints an error message
    pdf.SaveFile("hello.pdf")
} //                                                                        main

Samples:

Click on a sample to see the PDF in more detail.

[["Hello World!" sample image](demo/samples/hello.png)](demo/samples/hello.pdf)

[["Synergy Ipsum" sample image](demo/samples/corporate.png)](demo/samples/corporate.pdf)

Changelog:

These are the most recent changes in the functionality of the package, not including internal changes which are best seen in the commits history.

2018-04-14

• Changed CurrentPage from read-only to read/write property: added SetCurrentPage()
• Created PageCount() read-only property
• Created dingbats() demo to generate zapf_dingbats_table.pdf. You can use this table to look up the hex code for each icon.
• Changed text encoding from /WinAnsiEncoding to /StandardEncoding

See [changelog.md](./doc/changelog.md) for changes made earlier.

Roadmap:

• Achieve 100% test coverage
• Create a unit test for every method
• Unicode support
• Partial font embedding