Erweiterung von Kurt Jungs gopdf, das leider nicht weiterentwickelt wird
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package gofpdf
import (
// Attachment defines a content to be included in the pdf, in one
// of the following ways :
// - associated with the document as a whole : see SetAttachments()
// - accessible via a link localized on a page : see AddAttachmentAnnotation()
type Attachment struct {
Content []byte
// Filename is the displayed name of the attachment
Filename string
// Description is only displayed when using AddAttachmentAnnotation(),
// and might be modified by the pdf reader.
Description string
objectNumber int // filled when content is included
// return the hex encoded checksum of `data`
func checksum(data []byte) string {
tmp := md5.Sum(data)
sl := make([]byte, len(tmp))
for i, v := range tmp {
sl[i] = v
return hex.EncodeToString(sl)
// Writes a compressed file like object as ``/EmbeddedFile``. Compressing is
// done with deflate. Includes length, compressed length and MD5 checksum.
func (f *Fpdf) writeCompressedFileObject(content []byte) {
lenUncompressed := len(content)
sum := checksum(content)
compressed := sliceCompress(content)
lenCompressed := len(compressed)
f.outf("<< /Type /EmbeddedFile /Length %d /Filter /FlateDecode /Params << /CheckSum <%s> /Size %d >> >>\n",
lenCompressed, sum, lenUncompressed)
// Embed includes the content of `a`, and update its internal reference.
func (f *Fpdf) embed(a *Attachment) {
if a.objectNumber != 0 { // already embedded (objectNumber start at 2)
oldState := f.state
f.state = 1 // we write file content in the main buffer
streamID := f.n
f.outf("<< /Type /Filespec /F () /UF %s /EF << /F %d 0 R >> /Desc %s\n>>",
a.objectNumber = f.n
f.state = oldState
// SetAttachments writes attachments as embedded files (document attachment).
// These attachments are global, see AddAttachmentAnnotation() for a link
// anchored in a page. Note that only the last call of SetAttachments is
// useful, previous calls are discarded. Be aware that not all PDF readers
// support document attachments. See the SetAttachment example for a
// demonstration of this method.
func (f *Fpdf) SetAttachments(as []Attachment) {
f.attachments = as
// embed current attachments. store object numbers
// for later use by getEmbeddedFiles()
func (f *Fpdf) putAttachments() {
for i, a := range f.attachments {
f.attachments[i] = a
// return /EmbeddedFiles tree name catalog entry.
func (f Fpdf) getEmbeddedFiles() string {
names := make([]string, len(f.attachments))
for i, as := range f.attachments {
names[i] = fmt.Sprintf("(Attachement%d) %d 0 R ", i+1, as.objectNumber)
nameTree := fmt.Sprintf("<< /Names [\n %s \n] >>", strings.Join(names, "\n"))
return nameTree
// ---------------------------------- Annotations ----------------------------------
type annotationAttach struct {
x, y, w, h float64 // fpdf coordinates (y diff and scaling done)
// AddAttachmentAnnotation puts a link on the current page, on the rectangle
// defined by `x`, `y`, `w`, `h`. This link points towards the content defined
// in `a`, which is embedded in the document. Note than no drawing is done by
// this method : a method like `Cell()` or `Rect()` should be called to
// indicate to the reader that there is a link here. Requiring a pointer to an
// Attachment avoids useless copies in the resulting pdf: attachment pointing
// to the same data will have their content only be included once, and be
// shared amongst all links. Be aware that not all PDF readers support
// annotated attachments. See the AddAttachmentAnnotation example for a
// demonstration of this method.
func (f *Fpdf) AddAttachmentAnnotation(a *Attachment, x, y, w, h float64) {
if a == nil {
f.pageAttachments[] = append(f.pageAttachments[], annotationAttach{
Attachment: a,
x: x * f.k, y: f.hPt - y*f.k, w: w * f.k, h: h * f.k,
// embed current annotations attachments. store object numbers
// for later use by putAttachmentAnnotationLinks(), which is
// called for each page.
func (f *Fpdf) putAnnotationsAttachments() {
// avoid duplication
m := map[*Attachment]bool{}
for _, l := range f.pageAttachments {
for _, an := range l {
if m[an.Attachment] { // already embedded
func (f *Fpdf) putAttachmentAnnotationLinks(out *fmtBuffer, page int) {
for _, an := range f.pageAttachments[page] {
x1, y1, x2, y2 := an.x, an.y, an.x+an.w, an.y-an.h
as := fmt.Sprintf("<< /Type /XObject /Subtype /Form /BBox [%.2f %.2f %.2f %.2f] /Length 0 >>",
x1, y1, x2, y2)
as += "\nstream\nendstream"
out.printf("<< /Type /Annot /Subtype /FileAttachment /Rect [%.2f %.2f %.2f %.2f] /Border [0 0 0]\n",
x1, y1, x2, y2)
out.printf("/Contents %s ", f.textstring(utf8toutf16(an.Description)))
out.printf("/T %s ", f.textstring(utf8toutf16(an.Filename)))
out.printf("/AP << /N %s>>", as)
out.printf("/FS %d 0 R >>\n", an.objectNumber)