mirror of
https://github.com/superseriousbusiness/gotosocial.git
synced 2024-11-25 09:51:01 +00:00
777 lines
20 KiB
Go
777 lines
20 KiB
Go
// Copyright 2011 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// Package tiff implements a TIFF image decoder and encoder.
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//
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// The TIFF specification is at http://partners.adobe.com/public/developer/en/tiff/TIFF6.pdf
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package tiff // import "golang.org/x/image/tiff"
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import (
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"bytes"
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"compress/zlib"
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"encoding/binary"
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"fmt"
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"image"
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"image/color"
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"io"
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"math"
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"golang.org/x/image/ccitt"
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"golang.org/x/image/tiff/lzw"
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)
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// A FormatError reports that the input is not a valid TIFF image.
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type FormatError string
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func (e FormatError) Error() string {
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return "tiff: invalid format: " + string(e)
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}
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// An UnsupportedError reports that the input uses a valid but
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// unimplemented feature.
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type UnsupportedError string
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func (e UnsupportedError) Error() string {
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return "tiff: unsupported feature: " + string(e)
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}
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var errNoPixels = FormatError("not enough pixel data")
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const maxChunkSize = 10 << 20 // 10M
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// safeReadtAt is a verbatim copy of internal/saferio.ReadDataAt from the
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// standard library, which is used to read data from a reader using a length
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// provided by untrusted data, without allocating the entire slice ahead of time
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// if it is large (>maxChunkSize). This allows us to avoid allocating giant
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// slices before learning that we can't actually read that much data from the
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// reader.
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func safeReadAt(r io.ReaderAt, n uint64, off int64) ([]byte, error) {
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if int64(n) < 0 || n != uint64(int(n)) {
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// n is too large to fit in int, so we can't allocate
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// a buffer large enough. Treat this as a read failure.
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return nil, io.ErrUnexpectedEOF
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}
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if n < maxChunkSize {
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buf := make([]byte, n)
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_, err := r.ReadAt(buf, off)
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if err != nil {
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// io.SectionReader can return EOF for n == 0,
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// but for our purposes that is a success.
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if err != io.EOF || n > 0 {
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return nil, err
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}
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}
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return buf, nil
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}
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var buf []byte
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buf1 := make([]byte, maxChunkSize)
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for n > 0 {
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next := n
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if next > maxChunkSize {
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next = maxChunkSize
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}
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_, err := r.ReadAt(buf1[:next], off)
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if err != nil {
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return nil, err
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}
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buf = append(buf, buf1[:next]...)
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n -= next
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off += int64(next)
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}
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return buf, nil
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}
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type decoder struct {
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r io.ReaderAt
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byteOrder binary.ByteOrder
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config image.Config
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mode imageMode
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bpp uint
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features map[int][]uint
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palette []color.Color
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buf []byte
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off int // Current offset in buf.
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v uint32 // Buffer value for reading with arbitrary bit depths.
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nbits uint // Remaining number of bits in v.
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}
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// firstVal returns the first uint of the features entry with the given tag,
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// or 0 if the tag does not exist.
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func (d *decoder) firstVal(tag int) uint {
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f := d.features[tag]
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if len(f) == 0 {
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return 0
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}
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return f[0]
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}
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// ifdUint decodes the IFD entry in p, which must be of the Byte, Short
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// or Long type, and returns the decoded uint values.
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func (d *decoder) ifdUint(p []byte) (u []uint, err error) {
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var raw []byte
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if len(p) < ifdLen {
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return nil, FormatError("bad IFD entry")
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}
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datatype := d.byteOrder.Uint16(p[2:4])
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if dt := int(datatype); dt <= 0 || dt >= len(lengths) {
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return nil, UnsupportedError("IFD entry datatype")
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}
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count := d.byteOrder.Uint32(p[4:8])
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if count > math.MaxInt32/lengths[datatype] {
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return nil, FormatError("IFD data too large")
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}
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if datalen := lengths[datatype] * count; datalen > 4 {
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// The IFD contains a pointer to the real value.
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raw, err = safeReadAt(d.r, uint64(datalen), int64(d.byteOrder.Uint32(p[8:12])))
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} else {
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raw = p[8 : 8+datalen]
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}
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if err != nil {
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return nil, err
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}
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u = make([]uint, count)
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switch datatype {
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case dtByte:
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for i := uint32(0); i < count; i++ {
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u[i] = uint(raw[i])
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}
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case dtShort:
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for i := uint32(0); i < count; i++ {
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u[i] = uint(d.byteOrder.Uint16(raw[2*i : 2*(i+1)]))
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}
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case dtLong:
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for i := uint32(0); i < count; i++ {
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u[i] = uint(d.byteOrder.Uint32(raw[4*i : 4*(i+1)]))
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}
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default:
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return nil, UnsupportedError("data type")
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}
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return u, nil
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}
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// parseIFD decides whether the IFD entry in p is "interesting" and
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// stows away the data in the decoder. It returns the tag number of the
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// entry and an error, if any.
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func (d *decoder) parseIFD(p []byte) (int, error) {
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tag := d.byteOrder.Uint16(p[0:2])
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switch tag {
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case tBitsPerSample,
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tExtraSamples,
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tPhotometricInterpretation,
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tCompression,
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tPredictor,
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tStripOffsets,
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tStripByteCounts,
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tRowsPerStrip,
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tTileWidth,
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tTileLength,
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tTileOffsets,
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tTileByteCounts,
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tImageLength,
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tImageWidth,
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tFillOrder,
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tT4Options,
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tT6Options:
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val, err := d.ifdUint(p)
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if err != nil {
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return 0, err
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}
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d.features[int(tag)] = val
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case tColorMap:
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val, err := d.ifdUint(p)
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if err != nil {
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return 0, err
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}
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numcolors := len(val) / 3
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if len(val)%3 != 0 || numcolors <= 0 || numcolors > 256 {
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return 0, FormatError("bad ColorMap length")
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}
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d.palette = make([]color.Color, numcolors)
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for i := 0; i < numcolors; i++ {
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d.palette[i] = color.RGBA64{
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uint16(val[i]),
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uint16(val[i+numcolors]),
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uint16(val[i+2*numcolors]),
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0xffff,
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}
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}
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case tSampleFormat:
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// Page 27 of the spec: If the SampleFormat is present and
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// the value is not 1 [= unsigned integer data], a Baseline
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// TIFF reader that cannot handle the SampleFormat value
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// must terminate the import process gracefully.
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val, err := d.ifdUint(p)
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if err != nil {
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return 0, err
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}
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for _, v := range val {
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if v != 1 {
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return 0, UnsupportedError("sample format")
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}
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}
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}
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return int(tag), nil
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}
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// readBits reads n bits from the internal buffer starting at the current offset.
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func (d *decoder) readBits(n uint) (v uint32, ok bool) {
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for d.nbits < n {
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d.v <<= 8
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if d.off >= len(d.buf) {
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return 0, false
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}
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d.v |= uint32(d.buf[d.off])
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d.off++
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d.nbits += 8
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}
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d.nbits -= n
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rv := d.v >> d.nbits
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d.v &^= rv << d.nbits
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return rv, true
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}
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// flushBits discards the unread bits in the buffer used by readBits.
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// It is used at the end of a line.
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func (d *decoder) flushBits() {
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d.v = 0
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d.nbits = 0
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}
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// minInt returns the smaller of x or y.
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func minInt(a, b int) int {
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if a <= b {
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return a
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}
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return b
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}
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// decode decodes the raw data of an image.
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// It reads from d.buf and writes the strip or tile into dst.
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func (d *decoder) decode(dst image.Image, xmin, ymin, xmax, ymax int) error {
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d.off = 0
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// Apply horizontal predictor if necessary.
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// In this case, p contains the color difference to the preceding pixel.
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// See page 64-65 of the spec.
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if d.firstVal(tPredictor) == prHorizontal {
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switch d.bpp {
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case 16:
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var off int
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n := 2 * len(d.features[tBitsPerSample]) // bytes per sample times samples per pixel
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for y := ymin; y < ymax; y++ {
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off += n
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for x := 0; x < (xmax-xmin-1)*n; x += 2 {
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if off+2 > len(d.buf) {
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return errNoPixels
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}
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v0 := d.byteOrder.Uint16(d.buf[off-n : off-n+2])
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v1 := d.byteOrder.Uint16(d.buf[off : off+2])
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d.byteOrder.PutUint16(d.buf[off:off+2], v1+v0)
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off += 2
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}
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}
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case 8:
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var off int
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n := 1 * len(d.features[tBitsPerSample]) // bytes per sample times samples per pixel
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for y := ymin; y < ymax; y++ {
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off += n
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for x := 0; x < (xmax-xmin-1)*n; x++ {
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if off >= len(d.buf) {
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return errNoPixels
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}
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d.buf[off] += d.buf[off-n]
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off++
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}
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}
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case 1:
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return UnsupportedError("horizontal predictor with 1 BitsPerSample")
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}
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}
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rMaxX := minInt(xmax, dst.Bounds().Max.X)
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rMaxY := minInt(ymax, dst.Bounds().Max.Y)
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switch d.mode {
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case mGray, mGrayInvert:
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if d.bpp == 16 {
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img := dst.(*image.Gray16)
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for y := ymin; y < rMaxY; y++ {
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for x := xmin; x < rMaxX; x++ {
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if d.off+2 > len(d.buf) {
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return errNoPixels
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}
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v := d.byteOrder.Uint16(d.buf[d.off : d.off+2])
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d.off += 2
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if d.mode == mGrayInvert {
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v = 0xffff - v
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}
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img.SetGray16(x, y, color.Gray16{v})
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}
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if rMaxX == img.Bounds().Max.X {
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d.off += 2 * (xmax - img.Bounds().Max.X)
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}
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}
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} else {
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img := dst.(*image.Gray)
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max := uint32((1 << d.bpp) - 1)
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for y := ymin; y < rMaxY; y++ {
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for x := xmin; x < rMaxX; x++ {
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v, ok := d.readBits(d.bpp)
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if !ok {
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return errNoPixels
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}
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v = v * 0xff / max
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if d.mode == mGrayInvert {
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v = 0xff - v
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}
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img.SetGray(x, y, color.Gray{uint8(v)})
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}
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d.flushBits()
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}
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}
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case mPaletted:
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img := dst.(*image.Paletted)
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for y := ymin; y < rMaxY; y++ {
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for x := xmin; x < rMaxX; x++ {
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v, ok := d.readBits(d.bpp)
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if !ok {
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return errNoPixels
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}
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img.SetColorIndex(x, y, uint8(v))
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}
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d.flushBits()
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}
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case mRGB:
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if d.bpp == 16 {
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img := dst.(*image.RGBA64)
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for y := ymin; y < rMaxY; y++ {
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for x := xmin; x < rMaxX; x++ {
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if d.off+6 > len(d.buf) {
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return errNoPixels
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}
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r := d.byteOrder.Uint16(d.buf[d.off+0 : d.off+2])
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g := d.byteOrder.Uint16(d.buf[d.off+2 : d.off+4])
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b := d.byteOrder.Uint16(d.buf[d.off+4 : d.off+6])
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d.off += 6
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img.SetRGBA64(x, y, color.RGBA64{r, g, b, 0xffff})
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}
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}
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} else {
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img := dst.(*image.RGBA)
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for y := ymin; y < rMaxY; y++ {
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min := img.PixOffset(xmin, y)
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max := img.PixOffset(rMaxX, y)
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off := (y - ymin) * (xmax - xmin) * 3
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for i := min; i < max; i += 4 {
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if off+3 > len(d.buf) {
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return errNoPixels
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}
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img.Pix[i+0] = d.buf[off+0]
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img.Pix[i+1] = d.buf[off+1]
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img.Pix[i+2] = d.buf[off+2]
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img.Pix[i+3] = 0xff
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off += 3
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}
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}
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}
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case mNRGBA:
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if d.bpp == 16 {
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img := dst.(*image.NRGBA64)
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for y := ymin; y < rMaxY; y++ {
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for x := xmin; x < rMaxX; x++ {
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if d.off+8 > len(d.buf) {
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return errNoPixels
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}
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r := d.byteOrder.Uint16(d.buf[d.off+0 : d.off+2])
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g := d.byteOrder.Uint16(d.buf[d.off+2 : d.off+4])
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b := d.byteOrder.Uint16(d.buf[d.off+4 : d.off+6])
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a := d.byteOrder.Uint16(d.buf[d.off+6 : d.off+8])
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d.off += 8
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img.SetNRGBA64(x, y, color.NRGBA64{r, g, b, a})
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}
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}
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} else {
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img := dst.(*image.NRGBA)
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for y := ymin; y < rMaxY; y++ {
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min := img.PixOffset(xmin, y)
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max := img.PixOffset(rMaxX, y)
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i0, i1 := (y-ymin)*(xmax-xmin)*4, (y-ymin+1)*(xmax-xmin)*4
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if i1 > len(d.buf) {
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return errNoPixels
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}
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copy(img.Pix[min:max], d.buf[i0:i1])
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}
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}
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case mRGBA:
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if d.bpp == 16 {
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img := dst.(*image.RGBA64)
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for y := ymin; y < rMaxY; y++ {
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for x := xmin; x < rMaxX; x++ {
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if d.off+8 > len(d.buf) {
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return errNoPixels
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}
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r := d.byteOrder.Uint16(d.buf[d.off+0 : d.off+2])
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g := d.byteOrder.Uint16(d.buf[d.off+2 : d.off+4])
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b := d.byteOrder.Uint16(d.buf[d.off+4 : d.off+6])
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a := d.byteOrder.Uint16(d.buf[d.off+6 : d.off+8])
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d.off += 8
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img.SetRGBA64(x, y, color.RGBA64{r, g, b, a})
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}
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}
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} else {
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img := dst.(*image.RGBA)
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for y := ymin; y < rMaxY; y++ {
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min := img.PixOffset(xmin, y)
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max := img.PixOffset(rMaxX, y)
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i0, i1 := (y-ymin)*(xmax-xmin)*4, (y-ymin+1)*(xmax-xmin)*4
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if i1 > len(d.buf) {
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return errNoPixels
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}
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copy(img.Pix[min:max], d.buf[i0:i1])
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}
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}
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}
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return nil
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}
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func newDecoder(r io.Reader) (*decoder, error) {
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d := &decoder{
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r: newReaderAt(r),
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features: make(map[int][]uint),
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}
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p := make([]byte, 8)
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if _, err := d.r.ReadAt(p, 0); err != nil {
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if err == io.EOF {
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err = io.ErrUnexpectedEOF
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}
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return nil, err
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}
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switch string(p[0:4]) {
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case leHeader:
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d.byteOrder = binary.LittleEndian
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case beHeader:
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d.byteOrder = binary.BigEndian
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default:
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return nil, FormatError("malformed header")
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}
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ifdOffset := int64(d.byteOrder.Uint32(p[4:8]))
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// The first two bytes contain the number of entries (12 bytes each).
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if _, err := d.r.ReadAt(p[0:2], ifdOffset); err != nil {
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return nil, err
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}
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numItems := int(d.byteOrder.Uint16(p[0:2]))
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// All IFD entries are read in one chunk.
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var err error
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p, err = safeReadAt(d.r, uint64(ifdLen*numItems), ifdOffset+2)
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if err != nil {
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return nil, err
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}
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prevTag := -1
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for i := 0; i < len(p); i += ifdLen {
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tag, err := d.parseIFD(p[i : i+ifdLen])
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if err != nil {
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return nil, err
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}
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if tag <= prevTag {
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return nil, FormatError("tags are not sorted in ascending order")
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}
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prevTag = tag
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}
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d.config.Width = int(d.firstVal(tImageWidth))
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d.config.Height = int(d.firstVal(tImageLength))
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if _, ok := d.features[tBitsPerSample]; !ok {
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// Default is 1 per specification.
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d.features[tBitsPerSample] = []uint{1}
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}
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d.bpp = d.firstVal(tBitsPerSample)
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switch d.bpp {
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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")
|
|
}
|
|
if d.firstVal(tPhotometricInterpretation) != pRGB {
|
|
if len(d.features[tBitsPerSample]) != 1 {
|
|
return nil, UnsupportedError("extra samples")
|
|
}
|
|
}
|
|
|
|
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))
|
|
|
|
// The specification says that tile widths and lengths must be a multiple of 16.
|
|
// We currently permit invalid sizes, but reject anything too small to limit the
|
|
// amount of work a malicious input can force us to perform.
|
|
if blockWidth < 8 || blockHeight < 8 {
|
|
return nil, FormatError("tile size is too small")
|
|
}
|
|
|
|
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)
|
|
}
|
|
}
|
|
|
|
if blocksAcross == 0 || blocksDown == 0 {
|
|
return
|
|
}
|
|
// Maximum data per pixel is 8 bytes (RGBA64).
|
|
blockMaxDataSize := int64(blockWidth) * int64(blockHeight) * 8
|
|
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, err = safeReadAt(d.r, uint64(n), 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 = readBuf(r, d.buf, blockMaxDataSize)
|
|
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 = readBuf(r, d.buf, blockMaxDataSize)
|
|
case cLZW:
|
|
r := lzw.NewReader(io.NewSectionReader(d.r, offset, n), lzw.MSB, 8)
|
|
d.buf, err = readBuf(r, d.buf, blockMaxDataSize)
|
|
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 = readBuf(r, d.buf, blockMaxDataSize)
|
|
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 readBuf(r io.Reader, buf []byte, lim int64) ([]byte, error) {
|
|
b := bytes.NewBuffer(buf[:0])
|
|
_, err := b.ReadFrom(io.LimitReader(r, lim))
|
|
return b.Bytes(), err
|
|
}
|
|
|
|
func init() {
|
|
image.RegisterFormat("tiff", leHeader, Decode, DecodeConfig)
|
|
image.RegisterFormat("tiff", beHeader, Decode, DecodeConfig)
|
|
}
|