github.com/pdfcpu/pdfcpu@v0.11.1/pkg/filter/dctDecode.go (about)

     1  /*
     2  Copyright 2021 The pdfcpu Authors.
     3  
     4  Licensed under the Apache License, Version 2.0 (the "License");
     5  you may not use this file except in compliance with the License.
     6  You may obtain a copy of the License at
     7  
     8  	http://www.apache.org/licenses/LICENSE-2.0
     9  
    10  Unless required by applicable law or agreed to in writing, software
    11  distributed under the License is distributed on an "AS IS" BASIS,
    12  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    13  See the License for the specific language governing permissions and
    14  limitations under the License.
    15  */
    16  
    17  package filter
    18  
    19  import (
    20  	"bytes"
    21  	"encoding/gob"
    22  	"image/jpeg"
    23  	"io"
    24  )
    25  
    26  type dctDecode struct {
    27  	baseFilter
    28  }
    29  
    30  // Encode implements encoding for a DCTDecode filter.
    31  func (f dctDecode) Encode(r io.Reader) (io.Reader, error) {
    32  
    33  	return nil, nil
    34  }
    35  
    36  // Decode implements decoding for a DCTDecode filter.
    37  func (f dctDecode) Decode(r io.Reader) (io.Reader, error) {
    38  	return f.DecodeLength(r, -1)
    39  }
    40  
    41  func (f dctDecode) DecodeLength(r io.Reader, maxLen int64) (io.Reader, error) {
    42  	im, err := jpeg.Decode(r)
    43  	if err != nil {
    44  		return nil, err
    45  	}
    46  
    47  	var b bytes.Buffer
    48  
    49  	enc := gob.NewEncoder(&b)
    50  
    51  	if err := enc.Encode(im); err != nil {
    52  		return nil, err
    53  	}
    54  
    55  	return &b, nil
    56  }