// Copyright 2011 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// Package tiff implements a TIFF image decoder and encoder.
//
// The TIFF specification is at http://partners.adobe.com/public/developer/en/tiff/TIFF6.pdf
package tiff // import "golang.org/x/image/tiff"
import (
"compress/zlib"
"encoding/binary"
"fmt"
"image"
"image/color"
"io"
"io/ioutil"
"math"
"golang.org/x/image/ccitt"
"golang.org/x/image/tiff/lzw"
)
// A FormatError reports that the input is not a valid TIFF image.
type FormatError string
func (e FormatError) Error() string {
return "tiff: invalid format: " + string(e)
}
// An UnsupportedError reports that the input uses a valid but
// unimplemented feature.
type UnsupportedError string
func (e UnsupportedError) Error() string {
return "tiff: unsupported feature: " + string(e)
}
var errNoPixels = FormatError("not enough pixel data")
type decoder struct {
r io.ReaderAt
byteOrder binary.ByteOrder
config image.Config
mode imageMode
bpp uint
features map[int][]uint
palette []color.Color
buf []byte
off int // Current offset in buf.
v uint32 // Buffer value for reading with arbitrary bit depths.
nbits uint // Remaining number of bits in v.
}
// firstVal returns the first uint of the features entry with the given tag,
// or 0 if the tag does not exist.
func (d *decoder) firstVal(tag int) uint {
f := d.features[tag]
if len(f) == 0 {
return 0
}
return f[0]
}
// ifdUint decodes the IFD entry in p, which must be of the Byte, Short
// or Long type, and returns the decoded uint values.
func (d *decoder) ifdUint(p []byte) (u []uint, err error) {
var raw []byte
if len(p) < ifdLen {
return nil, FormatError("bad IFD entry")
}
datatype := d.byteOrder.Uint16(p[2:4])
if dt := int(datatype); dt <= 0 || dt >= len(lengths) {
return nil, UnsupportedError("IFD entry datatype")
}
count := d.byteOrder.Uint32(p[4:8])
if count > math.MaxInt32/lengths[datatype] {
return nil, FormatError("IFD data too large")
}
if datalen := lengths[datatype] * count; datalen > 4 {
// The IFD contains a pointer to the real value.
raw = make([]byte, datalen)
_, err = d.r.ReadAt(raw, int64(d.byteOrder.Uint32(p[8:12])))
} else {
raw = p[8 : 8+datalen]
}
if err != nil {
return nil, err
}
u = make([]uint, count)
switch datatype {
case dtByte:
for i := uint32(0); i < count; i++ {
u[i] = uint(raw[i])
}
case dtShort:
for i := uint32(0); i < count; i++ {
u[i] = uint(d.byteOrder.Uint16(raw[2*i : 2*(i+1)]))
}
case dtLong:
for i := uint32(0); i < count; i++ {
u[i] = uint(d.byteOrder.Uint32(raw[4*i : 4*(i+1)]))
}
default:
return nil, UnsupportedError("data type")
}
return u, nil
}
// parseIFD decides whether the IFD entry in p is "interesting" and
// stows away the data in the decoder. It returns the tag number of the
// entry and an error, if any.
func (d *decoder) parseIFD(p []byte) (int, error) {
tag := d.byteOrder.Uint16(p[0:2])
switch tag {
case tBitsPerSample,
tExtraSamples,
tPhotometricInterpretation,
tCompression,
tPredictor,
tStripOffsets,
tStripByteCounts,
tRowsPerStrip,
tTileWidth,
tTileLength,
tTileOffsets,
tTileByteCounts,
tImageLength,
tImageWidth,
tFillOrder,
tT4Options,
tT6Options:
val, err := d.ifdUint(p)
if err != nil {
return 0, err
}
d.features[int(tag)] = val
case tColorMap:
val, err := d.ifdUint(p)
if err != nil {
return 0, err
}
numcolors := len(val) / 3
if len(val)%3 != 0 || numcolors <= 0 || numcolors > 256 {
return 0, FormatError("bad ColorMap length")
}
d.palette = make([]color.Color, numcolors)
for i := 0; i < numcolors; i++ {
d.palette[i] = color.RGBA64{
uint16(val[i]),
uint16(val[i+numcolors]),
uint16(val[i+2*numcolors]),
0xffff,
}
}
case tSampleFormat:
// Page 27 of the spec: If the SampleFormat is present and
// the value is not 1 [= unsigned integer data], a Baseline
// TIFF reader that cannot handle the SampleFormat value
// must terminate the import process gracefully.
val, err := d.ifdUint(p)
if err != nil {
return 0, err
}
for _, v := range val {
if v != 1 {
return 0, UnsupportedError("sample format")
}
}
}
return int(tag), nil
}
// readBits reads n bits from the internal buffer starting at the current offset.
func (d *decoder) readBits(n uint) (v uint32, ok bool) {
for d.nbits < n {
d.v <<= 8
if d.off >= len(d.buf) {
return 0, false
}
d.v |= uint32(d.buf[d.off])
d.off++
d.nbits += 8
}
d.nbits -= n
rv := d.v >> d.nbits
d.v &^= rv << d.nbits
return rv, true
}
// flushBits discards the unread bits in the buffer used by readBits.
// It is used at the end of a line.
func (d *decoder) flushBits() {
d.v = 0
d.nbits = 0
}
// minInt returns the smaller of x or y.
func minInt(a, b int) int {
if a <= b {
return a
}
return b
}
// decode decodes the raw data of an image.
// It reads from d.buf and writes the strip or tile into dst.
func (d *decoder) decode(dst image.Image, xmin, ymin, xmax, ymax int) error {
d.off = 0
// Apply horizontal predictor if necessary.
// In this case, p contains the color difference to the preceding pixel.
// See page 64-65 of the spec.
if d.firstVal(tPredictor) == prHorizontal {
switch d.bpp {
case 16:
var off int
n := 2 * len(d.features[tBitsPerSample]) // bytes per sample times samples per pixel
for y := ymin; y < ymax; y++ {
off += n
for x := 0; x < (xmax-xmin-1)*n; x += 2 {
if off+2 > len(d.buf) {
return errNoPixels
}
v0 := d.byteOrder.Uint16(d.buf[off-n : off-n+2])
v1 := d.byteOrder.Uint16(d.buf[off : off+2])
d.byteOrder.PutUint16(d.buf[off:off+2], v1+v0)
off += 2
}
}
case 8:
var off int
n := 1 * len(d.features[tBitsPerSample]) // bytes per sample times samples per pixel
for y := ymin; y < ymax; y++ {
off += n
for x := 0; x < (xmax-xmin-1)*n; x++ {
if off >= len(d.buf) {
return errNoPixels
}
d.buf[off] += d.buf[off-n]
off++
}
}
case 1:
return UnsupportedError("horizontal predictor with 1 BitsPerSample")
}
}
rMaxX := minInt(xmax, dst.Bounds().Max.X)
rMaxY := minInt(ymax, dst.Bounds().Max.Y)
switch d.mode {
case mGray, mGrayInvert:
if d.bpp == 16 {
img := dst.(*image.Gray16)
for y := ymin; y < rMaxY; y++ {
for x := xmin; x < rMaxX; x++ {
if d.off+2 > len(d.buf) {
return errNoPixels
}
v := d.byteOrder.Uint16(d.buf[d.off : d.off+2])
d.off += 2
if d.mode == mGrayInvert {
v = 0xffff - v
}
img.SetGray16(x, y, color.Gray16{v})
}
if rMaxX == img.Bounds().Max.X {
d.off += 2 * (xmax - img.Bounds().Max.X)
}
}
} else {
img := dst.(*image.Gray)
max := uint32((1 << d.bpp) - 1)
for y := ymin; y < rMaxY; y++ {
for x := xmin; x < rMaxX; x++ {
v, ok := d.readBits(d.bpp)
if !ok {
return errNoPixels
}
v = v * 0xff / max
if d.mode == mGrayInvert {
v = 0xff - v
}
img.SetGray(x, y, color.Gray{uint8(v)})
}
d.flushBits()
}
}
case mPaletted:
img := dst.(*image.Paletted)
for y := ymin; y < rMaxY; y++ {
for x := xmin; x < rMaxX; x++ {
v, ok := d.readBits(d.bpp)
if !ok {
return errNoPixels
}
img.SetColorIndex(x, y, uint8(v))
}
d.flushBits()
}
case mRGB:
if d.bpp == 16 {
img := dst.(*image.RGBA64)
for y := ymin; y < rMaxY; y++ {
for x := xmin; x < rMaxX; x++ {
if d.off+6 > len(d.buf) {
return errNoPixels
}
r := d.byteOrder.Uint16(d.buf[d.off+0 : d.off+2])
g := d.byteOrder.Uint16(d.buf[d.off+2 : d.off+4])
b := d.byteOrder.Uint16(d.buf[d.off+4 : d.off+6])
d.off += 6
img.SetRGBA64(x, y, color.RGBA64{r, g, b, 0xffff})
}
}
} else {
img := dst.(*image.RGBA)
for y := ymin; y < rMaxY; y++ {
min := img.PixOffset(xmin, y)
max := img.PixOffset(rMaxX, y)
off := (y - ymin) * (xmax - xmin) * 3
for i := min; i < max; i += 4 {
if off+3 > len(d.buf) {
return errNoPixels
}
img.Pix[i+0] = d.buf[off+0]
img.Pix[i+1] = d.buf[off+1]
img.Pix[i+2] = d.buf[off+2]
img.Pix[i+3] = 0xff
off += 3
}
}
}
case mNRGBA:
if d.bpp == 16 {
img := dst.(*image.NRGBA64)
for y := ymin; y < rMaxY; y++ {
for x := xmin; x < rMaxX; x++ {
if d.off+8 > len(d.buf) {
return errNoPixels
}
r := d.byteOrder.Uint16(d.buf[d.off+0 : d.off+2])
g := d.byteOrder.Uint16(d.buf[d.off+2 : d.off+4])
b := d.byteOrder.Uint16(d.buf[d.off+4 : d.off+6])
a := d.byteOrder.Uint16(d.buf[d.off+6 : d.off+8])
d.off += 8
img.SetNRGBA64(x, y, color.NRGBA64{r, g, b, a})
}
}
} else {
img := dst.(*image.NRGBA)
for y := ymin; y < rMaxY; y++ {
min := img.PixOffset(xmin, y)
max := img.PixOffset(rMaxX, y)
i0, i1 := (y-ymin)*(xmax-xmin)*4, (y-ymin+1)*(xmax-xmin)*4
if i1 > len(d.buf) {
return errNoPixels
}
copy(img.Pix[min:max], d.buf[i0:i1])
}
}
case mRGBA:
if d.bpp == 16 {
img := dst.(*image.RGBA64)
for y := ymin; y < rMaxY; y++ {
for x := xmin; x < rMaxX; x++ {
if d.off+8 > len(d.buf) {
return errNoPixels
}
r := d.byteOrder.Uint16(d.buf[d.off+0 : d.off+2])
g := d.byteOrder.Uint16(d.buf[d.off+2 : d.off+4])
b := d.byteOrder.Uint16(d.buf[d.off+4 : d.off+6])
a := d.byteOrder.Uint16(d.buf[d.off+6 : d.off+8])
d.off += 8
img.SetRGBA64(x, y, color.RGBA64{r, g, b, a})
}
}
} else {
img := dst.(*image.RGBA)
for y := ymin; y < rMaxY; y++ {
min := img.PixOffset(xmin, y)
max := img.PixOffset(rMaxX, y)
i0, i1 := (y-ymin)*(xmax-xmin)*4, (y-ymin+1)*(xmax-xmin)*4
if i1 > len(d.buf) {
return errNoPixels
}
copy(img.Pix[min:max], d.buf[i0:i1])
}
}
}
return nil
}
func newDecoder(r io.Reader) (*decoder, error) {
d := &decoder{
r: newReaderAt(r),
features: make(map[int][]uint),
}
p := make([]byte, 8)
if _, err := d.r.ReadAt(p, 0); err != nil {
if err == io.EOF {
err = io.ErrUnexpectedEOF
}
return nil, err
}
switch string(p[0:4]) {
case leHeader:
d.byteOrder = binary.LittleEndian
case beHeader:
d.byteOrder = binary.BigEndian
default:
return nil, FormatError("malformed header")
}
ifdOffset := int64(d.byteOrder.Uint32(p[4:8]))
// The first two bytes contain the number of entries (12 bytes each).
if _, err := d.r.ReadAt(p[0:2], ifdOffset); err != nil {
return nil, err
}
numItems := int(d.byteOrder.Uint16(p[0:2]))
// All IFD entries are read in one chunk.
p = make([]byte, ifdLen*numItems)
if _, err := d.r.ReadAt(p, ifdOffset+2); err != nil {
return nil, err
}
prevTag := -1
for i := 0; i < len(p); i += ifdLen {
tag, err := d.parseIFD(p[i : i+ifdLen])
if err != nil {
return nil, err
}
if tag <= prevTag {
return nil, FormatError("tags are not sorted in ascending order")
}
prevTag = tag
}
d.config.Width = int(d.firstVal(tImageWidth))
d.config.Height = int(d.firstVal(tImageLength))
if _, ok := d.features[tBitsPerSample]; !ok {
// Default is 1 per specification.
d.features[tBitsPerSample] = []uint{1}
}
d.bpp = d.firstVal(tBitsPerSample)
switch d.bpp {
case 0:
return nil, FormatError("BitsPerSample must not be 0")
case 1, 8, 16:
// Nothing to do, these are accepted by this implementation.
default:
return nil, UnsupportedError(fmt.Sprintf("BitsPerSample of %v", d.bpp))
}
// Determine the image mode.
switch d.firstVal(tPhotometricInterpretation) {
case pRGB:
if d.bpp == 16 {
for _, b := range d.features[tBitsPerSample] {
if b != 16 {
return nil, FormatError("wrong number of samples for 16bit RGB")
}
}
} else {
for _, b := range d.features[tBitsPerSample] {
if b != 8 {
return nil, FormatError("wrong number of samples for 8bit RGB")
}
}
}
// RGB images normally have 3 samples per pixel.
// If there are more, ExtraSamples (p. 31-32 of the spec)
// gives their meaning (usually an alpha channel).
//
// This implementation does not support extra samples
// of an unspecified type.
switch len(d.features[tBitsPerSample]) {
case 3:
d.mode = mRGB
if d.bpp == 16 {
d.config.ColorModel = color.RGBA64Model
} else {
d.config.ColorModel = color.RGBAModel
}
case 4:
switch d.firstVal(tExtraSamples) {
case 1:
d.mode = mRGBA
if d.bpp == 16 {
d.config.ColorModel = color.RGBA64Model
} else {
d.config.ColorModel = color.RGBAModel
}
case 2:
d.mode = mNRGBA
if d.bpp == 16 {
d.config.ColorModel = color.NRGBA64Model
} else {
d.config.ColorModel = color.NRGBAModel
}
default:
return nil, FormatError("wrong number of samples for RGB")
}
default:
return nil, FormatError("wrong number of samples for RGB")
}
case pPaletted:
d.mode = mPaletted
d.config.ColorModel = color.Palette(d.palette)
case pWhiteIsZero:
d.mode = mGrayInvert
if d.bpp == 16 {
d.config.ColorModel = color.Gray16Model
} else {
d.config.ColorModel = color.GrayModel
}
case pBlackIsZero:
d.mode = mGray
if d.bpp == 16 {
d.config.ColorModel = color.Gray16Model
} else {
d.config.ColorModel = color.GrayModel
}
default:
return nil, UnsupportedError("color model")
}
return d, nil
}
// DecodeConfig returns the color model and dimensions of a TIFF image without
// decoding the entire image.
func DecodeConfig(r io.Reader) (image.Config, error) {
d, err := newDecoder(r)
if err != nil {
return image.Config{}, err
}
return d.config, nil
}
func ccittFillOrder(tiffFillOrder uint) ccitt.Order {
if tiffFillOrder == 2 {
return ccitt.LSB
}
return ccitt.MSB
}
// Decode reads a TIFF image from r and returns it as an image.Image.
// The type of Image returned depends on the contents of the TIFF.
func Decode(r io.Reader) (img image.Image, err error) {
d, err := newDecoder(r)
if err != nil {
return
}
blockPadding := false
blockWidth := d.config.Width
blockHeight := d.config.Height
blocksAcross := 1
blocksDown := 1
if d.config.Width == 0 {
blocksAcross = 0
}
if d.config.Height == 0 {
blocksDown = 0
}
var blockOffsets, blockCounts []uint
if int(d.firstVal(tTileWidth)) != 0 {
blockPadding = true
blockWidth = int(d.firstVal(tTileWidth))
blockHeight = int(d.firstVal(tTileLength))
if blockWidth != 0 {
blocksAcross = (d.config.Width + blockWidth - 1) / blockWidth
}
if blockHeight != 0 {
blocksDown = (d.config.Height + blockHeight - 1) / blockHeight
}
blockCounts = d.features[tTileByteCounts]
blockOffsets = d.features[tTileOffsets]
} else {
if int(d.firstVal(tRowsPerStrip)) != 0 {
blockHeight = int(d.firstVal(tRowsPerStrip))
}
if blockHeight != 0 {
blocksDown = (d.config.Height + blockHeight - 1) / blockHeight
}
blockOffsets = d.features[tStripOffsets]
blockCounts = d.features[tStripByteCounts]
}
// Check if we have the right number of strips/tiles, offsets and counts.
if n := blocksAcross * blocksDown; len(blockOffsets) < n || len(blockCounts) < n {
return nil, FormatError("inconsistent header")
}
imgRect := image.Rect(0, 0, d.config.Width, d.config.Height)
switch d.mode {
case mGray, mGrayInvert:
if d.bpp == 16 {
img = image.NewGray16(imgRect)
} else {
img = image.NewGray(imgRect)
}
case mPaletted:
img = image.NewPaletted(imgRect, d.palette)
case mNRGBA:
if d.bpp == 16 {
img = image.NewNRGBA64(imgRect)
} else {
img = image.NewNRGBA(imgRect)
}
case mRGB, mRGBA:
if d.bpp == 16 {
img = image.NewRGBA64(imgRect)
} else {
img = image.NewRGBA(imgRect)
}
}
for i := 0; i < blocksAcross; i++ {
blkW := blockWidth
if !blockPadding && i == blocksAcross-1 && d.config.Width%blockWidth != 0 {
blkW = d.config.Width % blockWidth
}
for j := 0; j < blocksDown; j++ {
blkH := blockHeight
if !blockPadding && j == blocksDown-1 && d.config.Height%blockHeight != 0 {
blkH = d.config.Height % blockHeight
}
offset := int64(blockOffsets[j*blocksAcross+i])
n := int64(blockCounts[j*blocksAcross+i])
switch d.firstVal(tCompression) {
// According to the spec, Compression does not have a default value,
// but some tools interpret a missing Compression value as none so we do
// the same.
case cNone, 0:
if b, ok := d.r.(*buffer); ok {
d.buf, err = b.Slice(int(offset), int(n))
} else {
d.buf = make([]byte, n)
_, err = d.r.ReadAt(d.buf, offset)
}
case cG3:
inv := d.firstVal(tPhotometricInterpretation) == pWhiteIsZero
order := ccittFillOrder(d.firstVal(tFillOrder))
r := ccitt.NewReader(io.NewSectionReader(d.r, offset, n), order, ccitt.Group3, blkW, blkH, &ccitt.Options{Invert: inv, Align: false})
d.buf, err = ioutil.ReadAll(r)
case cG4:
inv := d.firstVal(tPhotometricInterpretation) == pWhiteIsZero
order := ccittFillOrder(d.firstVal(tFillOrder))
r := ccitt.NewReader(io.NewSectionReader(d.r, offset, n), order, ccitt.Group4, blkW, blkH, &ccitt.Options{Invert: inv, Align: false})
d.buf, err = ioutil.ReadAll(r)
case cLZW:
r := lzw.NewReader(io.NewSectionReader(d.r, offset, n), lzw.MSB, 8)
d.buf, err = ioutil.ReadAll(r)
r.Close()
case cDeflate, cDeflateOld:
var r io.ReadCloser
r, err = zlib.NewReader(io.NewSectionReader(d.r, offset, n))
if err != nil {
return nil, err
}
d.buf, err = ioutil.ReadAll(r)
r.Close()
case cPackBits:
d.buf, err = unpackBits(io.NewSectionReader(d.r, offset, n))
default:
err = UnsupportedError(fmt.Sprintf("compression value %d", d.firstVal(tCompression)))
}
if err != nil {
return nil, err
}
xmin := i * blockWidth
ymin := j * blockHeight
xmax := xmin + blkW
ymax := ymin + blkH
err = d.decode(img, xmin, ymin, xmax, ymax)
if err != nil {
return nil, err
}
}
}
return
}
func init() {
image.RegisterFormat("tiff", leHeader, Decode, DecodeConfig)
image.RegisterFormat("tiff", beHeader, Decode, DecodeConfig)
}
