doc.go

// Copyright ©2023 The go-pdf Authors. All rights reserved.
// Use of this source code is governed by a MIT-style
// license that can be found in the LICENSE file.

/*
Package fpdf implements a PDF document generator with high level
support for text, drawing and images.

# Features

-   UTF-8 support

-   Choice of measurement unit, page format and margins

-   Page header and footer management

-   Automatic page breaks, line breaks, and text justification

-   Inclusion of JPEG, PNG, GIF, TIFF and basic path-only SVG images

-   Colors, gradients and alpha channel transparency

-   Outline bookmarks

-   Internal and external links

-   TrueType, Type1 and encoding support

-   Page compression

-   Lines, Bézier curves, arcs, and ellipses

-   Rotation, scaling, skewing, translation, and mirroring

-   Clipping

-   Document protection

-   Layers

-   Templates

-   Barcodes

-   Charting facility

-   Import PDFs as templates

go-pdf/fpdf has no dependencies other than the Go standard library. All tests
pass on Linux, Mac and Windows platforms.

go-pdf/fpdf supports UTF-8 TrueType fonts and “right-to-left” languages. Note
that Chinese, Japanese, and Korean characters may not be included in
many general purpose fonts. For these languages, a specialized font (for
example, NotoSansSC for simplified Chinese) can be used.

Also, support is provided to automatically translate UTF-8 runes to code
page encodings for languages that have fewer than 256 glyphs.

# Installation

To install the package on your system, run

	go get github.com/go-pdf/fpdf

Later, to receive updates, run

	go get -u -v github.com/go-pdf/fpdf/...

# Quick Start

The following Go code generates a simple PDF file.

	pdf := fpdf.New("P", "mm", "A4", "")
	pdf.AddPage()
	pdf.SetFont("Arial", "B", 16)
	pdf.Cell(40, 10, "Hello, world")
	err := pdf.OutputFileAndClose("hello.pdf")

See the functions in the fpdf_test.go file (shown as examples in this
documentation) for more advanced PDF examples.

# Errors

If an error occurs in an Fpdf method, an internal error field is set.
After this occurs, Fpdf method calls typically return without performing
any operations and the error state is retained. This error management
scheme facilitates PDF generation since individual method calls do not
need to be examined for failure; it is generally sufficient to wait
until after Output() is called. For the same reason, if an error occurs
in the calling application during PDF generation, it may be desirable
for the application to transfer the error to the Fpdf instance by
calling the SetError() method or the SetErrorf() method. At any time
during the life cycle of the Fpdf instance, the error state can be
determined with a call to Ok() or Err(). The error itself can be
retrieved with a call to Error().

# Conversion Notes

This package is a relatively straightforward translation from the
original FPDF library written in PHP (despite the caveat in the
introduction to Effective Go). The API names have been retained even
though the Go idiom would suggest otherwise (for example, pdf.GetX() is
used rather than simply pdf.X()). The similarity of the two libraries
makes the original FPDF website a good source of information. It
includes a forum and FAQ.

However, some internal changes have been made. Page content is built up
using buffers (of type bytes.Buffer) rather than repeated string
concatenation. Errors are handled as explained above rather than
panicking. Output is generated through an interface of type io.Writer or
io.WriteCloser. A number of the original PHP methods behave differently
based on the type of the arguments that are passed to them; in these
cases additional methods have been exported to provide similar
functionality. Font definition files are produced in JSON rather than
PHP.

# Example PDFs

A side effect of running go test ./... is the production of a number of
example PDFs. These can be found in the go-pdf/fpdf/pdf directory after the
tests complete.

Please note that these examples run in the context of a test. In order
run an example as a standalone application, you’ll need to examine
fpdf_test.go for some helper routines, for example exampleFilename() and
summary().

Example PDFs can be compared with reference copies in order to verify
that they have been generated as expected. This comparison will be
performed if a PDF with the same name as the example PDF is placed in
the go-pdf/fpdf/pdf/reference directory and if the third argument to
ComparePDFFiles() in internal/example/example.go is true. (By default it
is false.) The routine that summarizes an example will look for this
file and, if found, will call ComparePDFFiles() to check the example PDF
for equality with its reference PDF. If differences exist between the
two files they will be printed to standard output and the test will
fail. If the reference file is missing, the comparison is considered to
succeed. In order to successfully compare two PDFs, the placement of
internal resources must be consistent and the internal creation
timestamps must be the same. To do this, the methods SetCatalogSort()
and SetCreationDate() need to be called for both files. This is done
automatically for all examples.

# Nonstandard Fonts

Nothing special is required to use the standard PDF fonts (courier,
helvetica, times, zapfdingbats) in your documents other than calling
SetFont().

You should use AddUTF8Font() or AddUTF8FontFromBytes() to add a TrueType
UTF-8 encoded font. Use RTL() and LTR() methods switch between
“right-to-left” and “left-to-right” mode.

In order to use a different non-UTF-8 TrueType or Type1 font, you will
need to generate a font definition file and, if the font will be
embedded into PDFs, a compressed version of the font file. This is done
by calling the MakeFont function or using the included makefont command
line utility. To create the utility, cd into the makefont subdirectory
and run “go build”. This will produce a standalone executable named
makefont. Select the appropriate encoding file from the font
subdirectory and run the command as in the following example.

	./makefont --embed --enc=../font/cp1252.map --dst=../font ../font/calligra.ttf

In your PDF generation code, call AddFont() to load the font and, as
with the standard fonts, SetFont() to begin using it. Most examples,
including the package example, demonstrate this method. Good sources of
free, open-source fonts include Google Fonts and DejaVu Fonts.

# Related Packages

The draw2d package is a two dimensional vector graphics library that can
generate output in different forms. It uses gofpdf for its document
production mode.

# Contributing Changes

gofpdf is a global community effort and you are invited to make it even
better. If you have implemented a new feature or corrected a problem,
please consider contributing your change to the project. A contribution
that does not directly pertain to the core functionality of gofpdf
should be placed in its own directory directly beneath the contrib
directory.

Here are guidelines for making submissions. Your change should

-   be compatible with the MIT License

-   be properly documented

-   be formatted with go fmt

-   include an example in fpdf_test.go if appropriate

-   conform to the standards of golint and go vet, that is, golint . and
go vet . should not generate any warnings

-   not diminish test coverage

Pull requests are the preferred means of accepting your changes.

# License

gofpdf is released under the MIT License. It is copyrighted by Kurt Jung
and the contributors acknowledged below.

# Acknowledgments

This package’s code and documentation are closely derived from the FPDF
library created by Olivier Plathey, and a number of font and image
resources are copied directly from it. Bruno Michel has provided
valuable assistance with the code. Drawing support is adapted from the
FPDF geometric figures script by David Hernández Sanz. Transparency
support is adapted from the FPDF transparency script by Martin Hall-May.
Support for gradients and clipping is adapted from FPDF scripts by
Andreas Würmser. Support for outline bookmarks is adapted from Olivier
Plathey by Manuel Cornes. Layer support is adapted from Olivier Plathey.
Support for transformations is adapted from the FPDF transformation
script by Moritz Wagner and Andreas Würmser. PDF protection is adapted
from the work of Klemen Vodopivec for the FPDF product. Lawrence
Kesteloot provided code to allow an image’s extent to be determined
prior to placement. Support for vertical alignment within a cell was
provided by Stefan Schroeder. Ivan Daniluk generalized the font and
image loading code to use the Reader interface while maintaining
backward compatibility. Anthony Starks provided code for the Polygon
function. Robert Lillack provided the Beziergon function and corrected
some naming issues with the internal curve function. Claudio Felber
provided implementations for dashed line drawing and generalized font
loading. Stani Michiels provided support for multi-segment path drawing
with smooth line joins, line join styles, enhanced fill modes, and has
helped greatly with package presentation and tests. Templating is
adapted by Marcus Downing from the FPDF_Tpl library created by Jan
Slabon and Setasign. Jelmer Snoeck contributed packages that generate a
variety of barcodes and help with registering images on the web. Jelmer
Snoek and Guillermo Pascual augmented the basic HTML functionality with
aligned text. Kent Quirk implemented backwards-compatible support for
reading DPI from images that support it, and for setting DPI manually
and then having it properly taken into account when calculating image
size. Paulo Coutinho provided support for static embedded fonts. Dan
Meyers added support for embedded JavaScript. David Fish added a generic
alias-replacement function to enable, among other things, table of
contents functionality. Andy Bakun identified and corrected a problem in
which the internal catalogs were not sorted stably. Paul Montag added
encoding and decoding functionality for templates, including images that
are embedded in templates; this allows templates to be stored
independently of gofpdf. Paul also added support for page boxes used in
printing PDF documents. Wojciech Matusiak added supported for word
spacing. Artem Korotkiy added support of UTF-8 fonts. Dave Barnes added
support for imported objects and templates. Brigham Thompson added
support for rounded rectangles. Joe Westcott added underline
functionality and optimized image storage. Benoit KUGLER contributed
support for rectangles with corners of unequal radius, modification
times, and for file attachments and annotations.

# Roadmap

-   Remove all legacy code page font support; use UTF-8 exclusively

-   Improve test coverage as reported by the coverage tool.
*/
package fpdf // import "github.com/go-pdf/fpdf"