func main() {
var buffer bytes.Buffer
enc := ascii85.NewEncoder(io.MultiWriter(os.Stdout, &buffer))
log.Println("encoding to stdout")
_, err := enc.Write(data())
enc.Close()
if err != nil {
log.Fatalf("failed encoding: %s", err)
}
println()
dec := ascii85.NewDecoder(&buffer)
log.Println("decoding to stdout")
io.Copy(os.Stdout, dec)
}
// pd.DecodedStream() returns decoded contents of a stream.
func (pd *PdfReaderT) DecodedStream(reference []byte) (DictionaryT, []byte) {
dic, data := pd.Stream(reference)
if f, ok := dic["/Filter"]; ok {
filter := pd.ForcedArray(f)
var decos [][]byte
if d, ok := dic["/DecodeParams"]; ok {
decos = pd.ForcedArray(d)
} else {
decos = make([][]byte, len(filter))
}
for ff := range filter {
deco := pd.Dic(decos[ff])
switch string(filter[ff]) {
case "/FlateDecode":
data = fancy.ReadAndClose(zlib.NewInflater(fancy.SliceReader(data)))
case "/LZWDecode":
early := true
if deco != nil {
if s, ok := deco["/EarlyChange"]; ok {
early = pd.Num(s) == 1
}
}
data = lzw.Decode(data, early)
case "/ASCII85Decode":
ds := data
for len(ds) > 1 && ds[len(ds)-1] < 33 {
ds = ds[0 : len(ds)-1]
}
if len(ds) >= 2 && ds[len(ds)-1] == '>' && ds[len(ds)-2] == '~' {
ds = ds[0 : len(ds)-2]
}
data = fancy.ReadAll(ascii85.NewDecoder(fancy.SliceReader(ds)))
case "/ASCIIHexDecode":
data = hex.Decode(string(data))
default:
data = []byte{}
}
}
}
return dic, data
}
func decodeStream(dic DictionaryT, data []byte) []byte {
if f, ok := dic["/Filter"]; ok {
filter := ForcedArray(f)
var decos [][]byte
if d, ok := dic["/DecodeParms"]; ok {
decos = ForcedArray(d)
} else {
decos = make([][]byte, len(filter))
}
for ff := range filter {
// XXX: if there are multiple filters but only one DecodeParams,
// it should be used for all filters
deco := Dictionary(decos[ff])
switch string(filter[ff]) {
case "/FlateDecode":
data = fancy.ReadAndClose(zlib.NewReader(fancy.SliceReader(data)))
case "/LZWDecode":
early := true
if deco != nil {
if s, ok := deco["/EarlyChange"]; ok {
early = num(s) == 1
}
}
data = lzw.Decode(data, early)
case "/ASCII85Decode":
ds := data
for len(ds) > 1 && ds[len(ds)-1] < 33 {
ds = ds[0 : len(ds)-1]
}
if len(ds) >= 2 && ds[len(ds)-1] == '>' && ds[len(ds)-2] == '~' {
ds = ds[0 : len(ds)-2]
}
data = fancy.ReadAll(ascii85.NewDecoder(fancy.SliceReader(ds)))
case "/ASCIIHexDecode":
data, _ = hex.DecodeString(string(data))
default:
util.Log("Unsupported filter", string(filter[ff]))
data = []byte{}
}
if s, ok := deco["/Predictor"]; ok {
pred := num(s)
switch {
case pred == 1:
// no predictor
case pred > 10:
colors := numdef(deco["/Colors"], 1)
columns := numdef(deco["/Columns"], 1)
bitspercomponent := numdef(deco["/BitsPerComponent"], 8)
util.Log("applying predictor", pred, colors, columns, bitspercomponent)
data = util.ApplyPNGPredictor(pred, colors, columns, bitspercomponent, data)
default:
util.Log("Unsupported predictor", pred)
return nil
}
}
}
}
return data
}
}
parameter := Dictionary{}
if i < len(parameters) {
parameter = parameters[i]
}
var err error
stream, err = decoder(stream, parameter)
if err != nil {
return nil, errors.New(string(filter) + ": " + err.Error())
}
}
return stream, nil
}
var decoders = map[Name]func([]byte, Dictionary) ([]byte, error){
Name("ASCII85Decode"): func(encoded []byte, dict Dictionary) ([]byte, error) {
// the -3 strips the end of data marker
return ioutil.ReadAll(ascii85.NewDecoder(bytes.NewBuffer(encoded[:len(encoded)-3])))
},
Name("FlateDecode"): func(encoded []byte, dict Dictionary) ([]byte, error) {
return ioutil.ReadAll(flate.NewReader(bytes.NewBuffer(encoded[2:])))
},
// There is some problem with LZWDecode and TestFilterExample3
// Name("LZWDecode"): func(encoded []byte, dict Dictionary) ([]byte, error) {
// return ioutil.ReadAll(lzw.NewReader(bytes.NewBuffer(encoded[:len(encoded)-3]), lzw.MSB, 8))
// },
}