Tryanks/pdfsign
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Add encoding

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This commit is contained in:
Jeroen Bobbeldijk
2017-09-17 11:00:06 +02:00
parent 322998775c
commit e9e71178d7
1 changed files with 42 additions and 10 deletions
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52
sign/pdfxref.go
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@@ -80,16 +80,14 @@ func (context *SignContext) writeXrefTable() error {
func (context *SignContext) writeXrefStream() error {
// @todo: DO NOT FORGET TO ADD SELF REFERENCE!!!
// @todo: fix format (columns) for stream
// @todo: add PNG-Up support.
var streamBytes bytes.Buffer
w := zlib.NewWriter(&streamBytes)
buffer := bytes.NewBuffer(nil)
// Create the new catalog xref line.
visual_signature_object_start_position := strconv.FormatInt(context.Filesize, 10)
visual_signature_xref_line := leftPad(visual_signature_object_start_position, "0", 10-len(visual_signature_object_start_position)) + " 00000 n \n"
// Write the new catalog xref line.
if _, err := w.Write([]byte(visual_signature_xref_line)); err != nil {
if _, err := buffer.Write([]byte(visual_signature_xref_line)); err != nil {
return err
}
@@ -98,7 +96,7 @@ func (context *SignContext) writeXrefStream() error {
catalog_xref_line := leftPad(catalog_object_start_position, "0", 10-len(catalog_object_start_position)) + " 00000 n \n"
// Write the new catalog xref line.
if _, err := w.Write([]byte(catalog_xref_line)); err != nil {
if _, err := buffer.Write([]byte(catalog_xref_line)); err != nil {
return err
}
@@ -107,7 +105,7 @@ func (context *SignContext) writeXrefStream() error {
info_xref_line := leftPad(info_object_start_position, "0", 10-len(info_object_start_position)) + " 00000 n \n"
// Write the new signature xref line.
if _, err := w.Write([]byte(info_xref_line)); err != nil {
if _, err := buffer.Write([]byte(info_xref_line)); err != nil {
return err
}
@@ -116,10 +114,14 @@ func (context *SignContext) writeXrefStream() error {
signature_xref_line := leftPad(signature_object_start_position, "0", 10-len(signature_object_start_position)) + " 00000 n \n"
// Write the new signature xref line.
if _, err := w.Write([]byte(signature_xref_line)); err != nil {
if _, err := buffer.Write([]byte(signature_xref_line)); err != nil {
return err
}
streamBytes, err := EncodePNGUPBytes(5, buffer.Bytes())
if err != nil {
return err
}
w.Close()
new_info := "Info " + strconv.FormatInt(int64(context.InfoData.ObjectId), 10) + " 0 R"
new_root := "Root " + strconv.FormatInt(int64(context.CatalogData.ObjectId), 10) + " 0 R"
@@ -130,7 +132,7 @@ func (context *SignContext) writeXrefStream() error {
id1 := hex.EncodeToString([]byte(id.Index(0).RawString()))
new_xref := strconv.Itoa(int(context.SignData.ObjectId + 1)) + " 0 obj\n"
new_xref += "<< /Type /XRef /Length " + strconv.Itoa(len(streamBytes.Bytes())) + " /Filter /FlateDecode /DecodeParms << /Columns 5 /Predictor 12 >> /W [ 1 3 1 ] /Prev " + strconv.FormatInt(context.PDFReader.XrefInformation.StartPos, 10) + " /Size " + strconv.FormatInt(context.PDFReader.XrefInformation.ItemCount+5, 10) + " /Index [ " + strconv.FormatInt(context.PDFReader.XrefInformation.ItemCount, 10) + " 5 ] /" + new_info + " /" + new_root + " /ID [<" + id0 + "><" + id1 + ">] >>\n"
new_xref += "<< /Type /XRef /Length " + strconv.Itoa(len(streamBytes)) + " /Filter /FlateDecode /DecodeParms << /Columns 5 /Predictor 12 >> /W [ 1 3 1 ] /Prev " + strconv.FormatInt(context.PDFReader.XrefInformation.StartPos, 10) + " /Size " + strconv.FormatInt(context.PDFReader.XrefInformation.ItemCount+5, 10) + " /Index [ " + strconv.FormatInt(context.PDFReader.XrefInformation.ItemCount, 10) + " 5 ] /" + new_info + " /" + new_root + " /ID [<" + id0 + "><" + id1 + ">] >>\n"
if _, err := context.OutputFile.Write([]byte(new_xref)); err != nil {
return err
}
@@ -139,7 +141,7 @@ func (context *SignContext) writeXrefStream() error {
return err
}
if _, err := context.OutputFile.Write(streamBytes.Bytes()); err != nil {
if _, err := context.OutputFile.Write(streamBytes); err != nil {
return err
}
@@ -149,3 +151,33 @@ func (context *SignContext) writeXrefStream() error {
return nil
}
func EncodePNGUPBytes(columns int, data []byte) ([]byte, error) {
// @todo: this is PNG SUB, we need PNG UP.
rowCount := len(data) / columns
if len(data)%columns != 0 {
return nil, errors.New("Invalid row/column length")
}
buffer := bytes.NewBuffer(nil)
tmpRowData := make([]byte, columns)
for i := 0; i < rowCount; i++ {
rowData := data[columns*i : columns*(i+1)]
tmpRowData[0] = rowData[0]
for j := 1; j < columns; j++ {
tmpRowData[j] = byte(int(rowData[j]-rowData[j-1]) % 256)
}
buffer.WriteByte(1)
buffer.Write(tmpRowData)
}
data = buffer.Bytes()
var b bytes.Buffer
w := zlib.NewWriter(&b)
w.Write(data)
w.Close()
return b.Bytes(), nil
}