gtsocial-umbx

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chunk_decoder.go (1877B)

      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 	// We don't decode this particular type.
     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 }