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|
package pngstructure
import (
"bytes"
"fmt"
"encoding/binary"
)
type ChunkDecoder struct {
}
func NewChunkDecoder() *ChunkDecoder {
return new(ChunkDecoder)
}
func (cd *ChunkDecoder) Decode(c *Chunk) (decoded interface{}, err error) {
switch c.Type {
case "IHDR":
return cd.decodeIHDR(c)
}
// We don't decode this 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) (*ChunkIHDR, error) {
var (
b = bytes.NewBuffer(c.Data)
ihdr = new(ChunkIHDR)
readf = func(data interface{}) error {
return binary.Read(b, binary.BigEndian, data)
}
)
if err := readf(&ihdr.Width); err != nil {
return nil, err
}
if err := readf(&ihdr.Height); err != nil {
return nil, err
}
if err := readf(&ihdr.BitDepth); err != nil {
return nil, err
}
if err := readf(&ihdr.ColorType); err != nil {
return nil, err
}
if err := readf(&ihdr.CompressionMethod); err != nil {
return nil, err
}
if err := readf(&ihdr.FilterMethod); err != nil {
return nil, err
}
if err := readf(&ihdr.InterlaceMethod); err != nil {
return nil, err
}
return ihdr, nil
}
|
