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package pngstructure
import (
"fmt"
"bytes"
"encoding/binary"
"github.com/dsoprea/go-logging"
)
type ChunkDecoder struct {
}
func NewChunkDecoder() *ChunkDecoder {
return new(ChunkDecoder)
}
func (cd *ChunkDecoder) Decode(c *Chunk) (decoded interface{}, err error) {
defer func() {
if state := recover(); state != nil {
err := log.Wrap(state.(error))
log.Panic(err)
}
}()
switch c.Type {
case "IHDR":
ihdr, err := cd.decodeIHDR(c)
log.PanicIf(err)
return ihdr, nil
}
// We don't decode this particular type.
return nil, nil
}
type ChunkIHDR struct {
Width uint32
Height uint32
BitDepth uint8
ColorType uint8
CompressionMethod uint8
FilterMethod uint8
InterlaceMethod uint8
}
func (ihdr *ChunkIHDR) String() string {
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)
}
func (cd *ChunkDecoder) decodeIHDR(c *Chunk) (ihdr *ChunkIHDR, err error) {
defer func() {
if state := recover(); state != nil {
err := log.Wrap(state.(error))
log.Panic(err)
}
}()
b := bytes.NewBuffer(c.Data)
ihdr = new(ChunkIHDR)
err = binary.Read(b, binary.BigEndian, &ihdr.Width)
log.PanicIf(err)
err = binary.Read(b, binary.BigEndian, &ihdr.Height)
log.PanicIf(err)
err = binary.Read(b, binary.BigEndian, &ihdr.BitDepth)
log.PanicIf(err)
err = binary.Read(b, binary.BigEndian, &ihdr.ColorType)
log.PanicIf(err)
err = binary.Read(b, binary.BigEndian, &ihdr.CompressionMethod)
log.PanicIf(err)
err = binary.Read(b, binary.BigEndian, &ihdr.FilterMethod)
log.PanicIf(err)
err = binary.Read(b, binary.BigEndian, &ihdr.InterlaceMethod)
log.PanicIf(err)
return ihdr, nil
}
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