82 lines
1.6 KiB
Go
82 lines
1.6 KiB
Go
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package pngstructure
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import (
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"bytes"
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"fmt"
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"encoding/binary"
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)
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type ChunkDecoder struct {
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}
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func NewChunkDecoder() *ChunkDecoder {
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return new(ChunkDecoder)
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}
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func (cd *ChunkDecoder) Decode(c *Chunk) (decoded interface{}, err error) {
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switch c.Type {
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case "IHDR":
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return cd.decodeIHDR(c)
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}
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// We don't decode this type.
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return nil, nil
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}
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type ChunkIHDR struct {
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Width uint32
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Height uint32
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BitDepth uint8
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ColorType uint8
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CompressionMethod uint8
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FilterMethod uint8
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InterlaceMethod uint8
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}
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func (ihdr *ChunkIHDR) String() string {
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return fmt.Sprintf("IHDR<WIDTH=(%d) HEIGHT=(%d) DEPTH=(%d) COLOR-TYPE=(%d) COMP-METHOD=(%d) FILTER-METHOD=(%d) INTRLC-METHOD=(%d)>",
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ihdr.Width, ihdr.Height, ihdr.BitDepth, ihdr.ColorType, ihdr.CompressionMethod, ihdr.FilterMethod, ihdr.InterlaceMethod,
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)
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}
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func (cd *ChunkDecoder) decodeIHDR(c *Chunk) (*ChunkIHDR, error) {
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var (
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b = bytes.NewBuffer(c.Data)
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ihdr = new(ChunkIHDR)
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readf = func(data interface{}) error {
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return binary.Read(b, binary.BigEndian, data)
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}
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)
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if err := readf(&ihdr.Width); err != nil {
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return nil, err
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}
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if err := readf(&ihdr.Height); err != nil {
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return nil, err
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}
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if err := readf(&ihdr.BitDepth); err != nil {
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return nil, err
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}
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if err := readf(&ihdr.ColorType); err != nil {
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return nil, err
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}
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if err := readf(&ihdr.CompressionMethod); err != nil {
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return nil, err
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}
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if err := readf(&ihdr.FilterMethod); err != nil {
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return nil, err
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}
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if err := readf(&ihdr.InterlaceMethod); err != nil {
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return nil, err
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}
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return ihdr, nil
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}
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