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imgproxy/image_size/tiff.go

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Go
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2019-10-10 15:20:25 +02:00
package imagesize
2019-09-27 13:49:52 +02:00
import (
"bufio"
"bytes"
"encoding/binary"
"io"
)
var (
tiffLeHeader = []byte("II\x2A\x00")
tiffBeHeader = []byte("MM\x00\x2A")
)
const (
tiffDtByte = 1
tiffDtShort = 3
tiffDtLong = 4
tiffImageWidth = 256
tiffImageLength = 257
)
type tiffReader interface {
io.Reader
Discard(n int) (discarded int, err error)
}
func asTiffReader(r io.Reader) tiffReader {
if rr, ok := r.(tiffReader); ok {
return rr
}
return bufio.NewReader(r)
}
type TiffFormatError string
func (e TiffFormatError) Error() string { return "invalid TIFF format: " + string(e) }
func DecodeTiffMeta(rr io.Reader) (*Meta, error) {
var (
tmp [12]byte
byteOrder binary.ByteOrder
)
r := asTiffReader(rr)
if _, err := io.ReadFull(r, tmp[:8]); err != nil {
return nil, err
}
switch {
case bytes.Equal(tiffLeHeader, tmp[0:4]):
byteOrder = binary.LittleEndian
case bytes.Equal(tiffBeHeader, tmp[0:4]):
byteOrder = binary.BigEndian
default:
return nil, TiffFormatError("malformed header")
}
ifdOffset := int(byteOrder.Uint32(tmp[4:8]))
if _, err := r.Discard(ifdOffset - 8); err != nil {
return nil, err
}
if _, err := io.ReadFull(r, tmp[0:2]); err != nil {
return nil, err
}
numItems := int(byteOrder.Uint16(tmp[0:2]))
var width, height int
for i := 0; i < numItems; i++ {
if _, err := io.ReadFull(r, tmp[:]); err != nil {
return nil, err
}
tag := byteOrder.Uint16(tmp[0:2])
if tag != tiffImageWidth && tag != tiffImageLength {
continue
}
datatype := byteOrder.Uint16(tmp[2:4])
var value int
switch datatype {
case tiffDtByte:
value = int(tmp[9])
case tiffDtShort:
value = int(byteOrder.Uint16(tmp[8:10]))
case tiffDtLong:
value = int(byteOrder.Uint32(tmp[8:12]))
default:
return nil, TiffFormatError("unsupported IFD entry datatype")
}
if tag == tiffImageWidth {
width = value
} else {
height = value
}
if width > 0 && height > 0 {
return &Meta{
Format: "tiff",
Width: width,
Height: height,
}, nil
}
}
return nil, TiffFormatError("image dimensions are not specified")
}
func init() {
RegisterFormat(string(tiffLeHeader), DecodeTiffMeta)
RegisterFormat(string(tiffBeHeader), DecodeTiffMeta)
}