1 package pngstructure
2
3 import (
4 "bytes"
5 "fmt"
6
7 "encoding/binary"
8
9 "github.com/dsoprea/go-logging"
10 )
11
12 type ChunkDecoder struct {
13 }
14
15 func NewChunkDecoder() *ChunkDecoder {
16 return new(ChunkDecoder)
17 }
18
19 func (cd *ChunkDecoder) Decode(c *Chunk) (decoded interface{}, err error) {
20 defer func() {
21 if state := recover(); state != nil {
22 err := log.Wrap(state.(error))
23 log.Panic(err)
24 }
25 }()
26
27 switch c.Type {
28 case "IHDR":
29 ihdr, err := cd.decodeIHDR(c)
30 log.PanicIf(err)
31
32 return ihdr, nil
33 }
34
35
36 return nil, nil
37 }
38
39 type ChunkIHDR struct {
40 Width uint32
41 Height uint32
42 BitDepth uint8
43 ColorType uint8
44 CompressionMethod uint8
45 FilterMethod uint8
46 InterlaceMethod uint8
47 }
48
49 func (ihdr *ChunkIHDR) String() string {
50 return fmt.Sprintf("IHDR<WIDTH=(%d) HEIGHT=(%d) DEPTH=(%d) COLOR-TYPE=(%d) COMP-METHOD=(%d) FILTER-METHOD=(%d) INTRLC-METHOD=(%d)>", ihdr.Width, ihdr.Height, ihdr.BitDepth, ihdr.ColorType, ihdr.CompressionMethod, ihdr.FilterMethod, ihdr.InterlaceMethod)
51 }
52
53 func (cd *ChunkDecoder) decodeIHDR(c *Chunk) (ihdr *ChunkIHDR, err error) {
54 defer func() {
55 if state := recover(); state != nil {
56 err := log.Wrap(state.(error))
57 log.Panic(err)
58 }
59 }()
60
61 b := bytes.NewBuffer(c.Data)
62
63 ihdr = new(ChunkIHDR)
64
65 err = binary.Read(b, binary.BigEndian, &ihdr.Width)
66 log.PanicIf(err)
67
68 err = binary.Read(b, binary.BigEndian, &ihdr.Height)
69 log.PanicIf(err)
70
71 err = binary.Read(b, binary.BigEndian, &ihdr.BitDepth)
72 log.PanicIf(err)
73
74 err = binary.Read(b, binary.BigEndian, &ihdr.ColorType)
75 log.PanicIf(err)
76
77 err = binary.Read(b, binary.BigEndian, &ihdr.CompressionMethod)
78 log.PanicIf(err)
79
80 err = binary.Read(b, binary.BigEndian, &ihdr.FilterMethod)
81 log.PanicIf(err)
82
83 err = binary.Read(b, binary.BigEndian, &ihdr.InterlaceMethod)
84 log.PanicIf(err)
85
86 return ihdr, nil
87 }
88
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