130 lines
3.6 KiB
Go
130 lines
3.6 KiB
Go
package core
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import (
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"fmt"
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"gitea.tecamino.com/paadi/pdfmerge/internal/pdf/common"
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)
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// NewEncoderFromStream creates a StreamEncoder based on the stream's dictionary.
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func NewEncoderFromStream(streamObj *PdfObjectStream) (StreamEncoder, error) {
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filterObj := TraceToDirectObject(streamObj.PdfObjectDictionary.Get("Filter"))
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if filterObj == nil {
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// No filter, return raw data back.
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return NewRawEncoder(), nil
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}
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if _, isNull := filterObj.(*PdfObjectNull); isNull {
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// Filter is null -> raw data.
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return NewRawEncoder(), nil
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}
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// The filter should be a name or an array with a list of filter names.
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method, ok := filterObj.(*PdfObjectName)
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if !ok {
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array, ok := filterObj.(*PdfObjectArray)
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if !ok {
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return nil, fmt.Errorf("filter not a Name or Array object")
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}
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if len(*array) == 0 {
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// Empty array -> indicates raw filter (no filter).
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return NewRawEncoder(), nil
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}
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if len(*array) != 1 {
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menc, err := newMultiEncoderFromStream(streamObj)
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if err != nil {
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common.Log.Error("Failed creating multi encoder: %v", err)
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return nil, err
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}
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common.Log.Trace("Multi enc: %s\n", menc)
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return menc, nil
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}
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// Single element.
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filterObj = (*array)[0]
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method, ok = filterObj.(*PdfObjectName)
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if !ok {
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return nil, fmt.Errorf("filter array member not a Name object")
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}
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}
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switch *method {
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case StreamEncodingFilterNameFlate:
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return newFlateEncoderFromStream(streamObj, nil)
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case StreamEncodingFilterNameLZW:
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return newLZWEncoderFromStream(streamObj, nil)
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case StreamEncodingFilterNameDCT:
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return newDCTEncoderFromStream(streamObj, nil)
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case StreamEncodingFilterNameRunLength:
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return newRunLengthEncoderFromStream()
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case StreamEncodingFilterNameASCIIHex:
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return NewASCIIHexEncoder(), nil
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case StreamEncodingFilterNameASCII85, "A85":
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return NewASCII85Encoder(), nil
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case StreamEncodingFilterNameCCITTFax:
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return NewCCITTFaxEncoder(), nil
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case StreamEncodingFilterNameJBIG2:
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return NewJBIG2Encoder(), nil
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case StreamEncodingFilterNameJPX:
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return NewJPXEncoder(), nil
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default:
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common.Log.Debug("error: Unsupported encoding method!")
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return nil, fmt.Errorf("unsupported encoding method (%s)", *method)
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}
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}
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// DecodeStream decodes the stream data and returns the decoded data.
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// An error is returned upon failure.
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func DecodeStream(streamObj *PdfObjectStream) ([]byte, error) {
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common.Log.Trace("Decode stream")
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encoder, err := NewEncoderFromStream(streamObj)
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if err != nil {
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common.Log.Debug("Stream decoding failed: %v", err)
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return nil, err
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}
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common.Log.Trace("Encoder: %#v\n", encoder)
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decoded, err := encoder.DecodeStream(streamObj)
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if err != nil {
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common.Log.Debug("Stream decoding failed: %v", err)
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return nil, err
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}
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return decoded, nil
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}
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// EncodeStream encodes the stream data using the encoded specified by the stream's dictionary.
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func EncodeStream(streamObj *PdfObjectStream) error {
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common.Log.Trace("Encode stream")
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encoder, err := NewEncoderFromStream(streamObj)
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if err != nil {
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common.Log.Debug("Stream decoding failed: %v", err)
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return err
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}
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if lzwenc, is := encoder.(*LZWEncoder); is {
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// If LZW:
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// Make sure to use EarlyChange 0.. We do not have write support for 1 yet.
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lzwenc.EarlyChange = 0
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streamObj.PdfObjectDictionary.Set("EarlyChange", MakeInteger(0))
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}
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common.Log.Trace("Encoder: %+v\n", encoder)
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encoded, err := encoder.EncodeBytes(streamObj.Stream)
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if err != nil {
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common.Log.Debug("Stream encoding failed: %v", err)
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return err
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}
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streamObj.Stream = encoded
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// Update length
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streamObj.PdfObjectDictionary.Set("Length", MakeInteger(int64(len(encoded))))
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return nil
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}
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