Tryanks/pdfsign
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Fix up stream

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This commit is contained in:
Jeroen Bobbeldijk
2017-09-17 12:33:49 +02:00
parent fa31007f97
commit 3d7049d4e8
1 changed files with 22 additions and 43 deletions
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65
sign/pdfxref.go
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@@ -6,7 +6,7 @@ import (
"encoding/hex"
"compress/zlib"
"bytes"
"log"
"encoding/binary"
)
func (context *SignContext) writeXref() error {
@@ -79,51 +79,19 @@ func (context *SignContext) writeXrefTable() error {
}
func (context *SignContext) writeXrefStream() error {
// @todo: add self reference.
// @todo: fix format (columns) for stream, first column is 1 (sub) or 2 (up)
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 := buffer.Write([]byte(visual_signature_xref_line)); err != nil {
return err
}
// Create the new catalog xref line.
catalog_object_start_position := strconv.FormatInt(context.Filesize+context.VisualSignData.Length, 10)
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 := buffer.Write([]byte(catalog_xref_line)); err != nil {
return err
}
// Create the new signature xref line.
info_object_start_position := strconv.FormatInt(context.Filesize+context.VisualSignData.Length+context.CatalogData.Length, 10)
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 := buffer.Write([]byte(info_xref_line)); err != nil {
return err
}
// Create the new signature xref line.
signature_object_start_position := strconv.FormatInt(context.Filesize+context.VisualSignData.Length+context.CatalogData.Length+context.InfoData.Length, 10)
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 := buffer.Write([]byte(signature_xref_line)); err != nil {
return err
}
predictor := context.PDFReader.Trailer().Key("DecodeParms").Key("Predictor").Int64()
streamBytes := []byte{}
err := errors.New("")
writeXrefStreamLine(buffer, 1, int(context.Filesize), 0)
writeXrefStreamLine(buffer, 1, int(context.Filesize+context.VisualSignData.Length), 0)
writeXrefStreamLine(buffer, 1, int(context.Filesize+context.VisualSignData.Length+context.CatalogData.Length), 0)
writeXrefStreamLine(buffer, 1, int(context.Filesize+context.VisualSignData.Length+context.CatalogData.Length+context.InfoData.Length), 0)
writeXrefStreamLine(buffer, 1, int(context.NewXrefStart), 0)
// If original uses PNG Sub, use that.
if predictor == 11 {
streamBytes, err = EncodePNGSUBBytes(5, buffer.Bytes())
@@ -168,6 +136,18 @@ func (context *SignContext) writeXrefStream() error {
return nil
}
func writeXrefStreamLine(b *bytes.Buffer, xreftype byte, offset int, gen byte) {
b.WriteByte(xreftype);
b.Write(encodeInt(offset));
b.WriteByte(gen);
}
func encodeInt(i int) []byte {
result := make([]byte, 4)
binary.BigEndian.PutUint32(result, uint32(i))
return result[1:4]
}
func EncodePNGSUBBytes(columns int, data []byte) ([]byte, error) {
rowCount := len(data) / columns
if len(data)%columns != 0 {
@@ -215,15 +195,14 @@ func EncodePNGUPBytes(columns int, data []byte) ([]byte, error) {
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++ {
for j := 0; j < columns; j++ {
tmpRowData[j] = byte(int(rowData[j]-prevRowData[j]) % 256)
}
// Save the previous row for prediction.
prevRowData = tmpRowData
copy(prevRowData, rowData)
buffer.WriteByte(1)
buffer.WriteByte(2)
buffer.Write(tmpRowData)
}