Update vendor for next release (#1343)

1 files changed, 795 insertions, 0 deletions

diff --git a/vendor/golang.org/x/image/ccitt/reader.go b/vendor/golang.org/x/image/ccitt/reader.go
new file mode 100644
index 00000000..340de053
--- /dev/null
+++ b/vendor/golang.org/x/image/ccitt/reader.go
@@ -0,0 +1,795 @@
+// Copyright 2019 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.
+
+//go:generate go run gen.go
+
+// Package ccitt implements a CCITT (fax) image decoder.
+package ccitt
+
+import (
+	"encoding/binary"
+	"errors"
+	"image"
+	"io"
+	"math/bits"
+)
+
+var (
+	errIncompleteCode          = errors.New("ccitt: incomplete code")
+	errInvalidBounds           = errors.New("ccitt: invalid bounds")
+	errInvalidCode             = errors.New("ccitt: invalid code")
+	errInvalidMode             = errors.New("ccitt: invalid mode")
+	errInvalidOffset           = errors.New("ccitt: invalid offset")
+	errMissingEOL              = errors.New("ccitt: missing End-of-Line")
+	errRunLengthOverflowsWidth = errors.New("ccitt: run length overflows width")
+	errRunLengthTooLong        = errors.New("ccitt: run length too long")
+	errUnsupportedMode         = errors.New("ccitt: unsupported mode")
+	errUnsupportedSubFormat    = errors.New("ccitt: unsupported sub-format")
+	errUnsupportedWidth        = errors.New("ccitt: unsupported width")
+)
+
+// Order specifies the bit ordering in a CCITT data stream.
+type Order uint32
+
+const (
+	// LSB means Least Significant Bits first.
+	LSB Order = iota
+	// MSB means Most Significant Bits first.
+	MSB
+)
+
+// SubFormat represents that the CCITT format consists of a number of
+// sub-formats. Decoding or encoding a CCITT data stream requires knowing the
+// sub-format context. It is not represented in the data stream per se.
+type SubFormat uint32
+
+const (
+	Group3 SubFormat = iota
+	Group4
+)
+
+// AutoDetectHeight is passed as the height argument to NewReader to indicate
+// that the image height (the number of rows) is not known in advance.
+const AutoDetectHeight = -1
+
+// Options are optional parameters.
+type Options struct {
+	// Align means that some variable-bit-width codes are byte-aligned.
+	Align bool
+	// Invert means that black is the 1 bit or 0xFF byte, and white is 0.
+	Invert bool
+}
+
+// maxWidth is the maximum (inclusive) supported width. This is a limitation of
+// this implementation, to guard against integer overflow, and not anything
+// inherent to the CCITT format.
+const maxWidth = 1 << 20
+
+func invertBytes(b []byte) {
+	for i, c := range b {
+		b[i] = ^c
+	}
+}
+
+func reverseBitsWithinBytes(b []byte) {
+	for i, c := range b {
+		b[i] = bits.Reverse8(c)
+	}
+}
+
+// highBits writes to dst (1 bit per pixel, most significant bit first) the
+// high (0x80) bits from src (1 byte per pixel). It returns the number of bytes
+// written and read such that dst[:d] is the packed form of src[:s].
+//
+// For example, if src starts with the 8 bytes [0x7D, 0x7E, 0x7F, 0x80, 0x81,
+// 0x82, 0x00, 0xFF] then 0x1D will be written to dst[0].
+//
+// If src has (8 * len(dst)) or more bytes then only len(dst) bytes are
+// written, (8 * len(dst)) bytes are read, and invert is ignored.
+//
+// Otherwise, if len(src) is not a multiple of 8 then the final byte written to
+// dst is padded with 1 bits (if invert is true) or 0 bits. If inverted, the 1s
+// are typically temporary, e.g. they will be flipped back to 0s by an
+// invertBytes call in the highBits caller, reader.Read.
+func highBits(dst []byte, src []byte, invert bool) (d int, s int) {
+	// Pack as many complete groups of 8 src bytes as we can.
+	n := len(src) / 8
+	if n > len(dst) {
+		n = len(dst)
+	}
+	dstN := dst[:n]
+	for i := range dstN {
+		src8 := src[i*8 : i*8+8]
+		dstN[i] = ((src8[0] & 0x80) >> 0) |
+			((src8[1] & 0x80) >> 1) |
+			((src8[2] & 0x80) >> 2) |
+			((src8[3] & 0x80) >> 3) |
+			((src8[4] & 0x80) >> 4) |
+			((src8[5] & 0x80) >> 5) |
+			((src8[6] & 0x80) >> 6) |
+			((src8[7] & 0x80) >> 7)
+	}
+	d, s = n, 8*n
+	dst, src = dst[d:], src[s:]
+
+	// Pack up to 7 remaining src bytes, if there's room in dst.
+	if (len(dst) > 0) && (len(src) > 0) {
+		dstByte := byte(0)
+		if invert {
+			dstByte = 0xFF >> uint(len(src))
+		}
+		for n, srcByte := range src {
+			dstByte |= (srcByte & 0x80) >> uint(n)
+		}
+		dst[0] = dstByte
+		d, s = d+1, s+len(src)
+	}
+	return d, s
+}
+
+type bitReader struct {
+	r io.Reader
+
+	// readErr is the error returned from the most recent r.Read call. As the
+	// io.Reader documentation says, when r.Read returns (n, err), "always
+	// process the n > 0 bytes returned before considering the error err".
+	readErr error
+
+	// order is whether to process r's bytes LSB first or MSB first.
+	order Order
+
+	// The high nBits bits of the bits field hold upcoming bits in MSB order.
+	bits  uint64
+	nBits uint32
+
+	// bytes[br:bw] holds bytes read from r but not yet loaded into bits.
+	br    uint32
+	bw    uint32
+	bytes [1024]uint8
+}
+
+func (b *bitReader) alignToByteBoundary() {
+	n := b.nBits & 7
+	b.bits <<= n
+	b.nBits -= n
+}
+
+// nextBitMaxNBits is the maximum possible value of bitReader.nBits after a
+// bitReader.nextBit call, provided that bitReader.nBits was not more than this
+// value before that call.
+//
+// Note that the decode function can unread bits, which can temporarily set the
+// bitReader.nBits value above nextBitMaxNBits.
+const nextBitMaxNBits = 31
+
+func (b *bitReader) nextBit() (uint64, error) {
+	for {
+		if b.nBits > 0 {
+			bit := b.bits >> 63
+			b.bits <<= 1
+			b.nBits--
+			return bit, nil
+		}
+
+		if available := b.bw - b.br; available >= 4 {
+			// Read 32 bits, even though b.bits is a uint64, since the decode
+			// function may need to unread up to maxCodeLength bits, putting
+			// them back in the remaining (64 - 32) bits. TestMaxCodeLength
+			// checks that the generated maxCodeLength constant fits.
+			//
+			// If changing the Uint32 call, also change nextBitMaxNBits.
+			b.bits = uint64(binary.BigEndian.Uint32(b.bytes[b.br:])) << 32
+			b.br += 4
+			b.nBits = 32
+			continue
+		} else if available > 0 {
+			b.bits = uint64(b.bytes[b.br]) << (7 * 8)
+			b.br++
+			b.nBits = 8
+			continue
+		}
+
+		if b.readErr != nil {
+			return 0, b.readErr
+		}
+
+		n, err := b.r.Read(b.bytes[:])
+		b.br = 0
+		b.bw = uint32(n)
+		b.readErr = err
+
+		if b.order != MSB {
+			reverseBitsWithinBytes(b.bytes[:b.bw])
+		}
+	}
+}
+
+func decode(b *bitReader, decodeTable [][2]int16) (uint32, error) {
+	nBitsRead, bitsRead, state := uint32(0), uint64(0), int32(1)
+	for {
+		bit, err := b.nextBit()
+		if err != nil {
+			if err == io.EOF {
+				err = errIncompleteCode
+			}
+			return 0, err
+		}
+		bitsRead |= bit << (63 - nBitsRead)
+		nBitsRead++
+
+		// The "&1" is redundant, but can eliminate a bounds check.
+		state = int32(decodeTable[state][bit&1])
+		if state < 0 {
+			return uint32(^state), nil
+		} else if state == 0 {
+			// Unread the bits we've read, then return errInvalidCode.
+			b.bits = (b.bits >> nBitsRead) | bitsRead
+			b.nBits += nBitsRead
+			return 0, errInvalidCode
+		}
+	}
+}
+
+// decodeEOL decodes the 12-bit EOL code 0000_0000_0001.
+func decodeEOL(b *bitReader) error {
+	nBitsRead, bitsRead := uint32(0), uint64(0)
+	for {
+		bit, err := b.nextBit()
+		if err != nil {
+			if err == io.EOF {
+				err = errMissingEOL
+			}
+			return err
+		}
+		bitsRead |= bit << (63 - nBitsRead)
+		nBitsRead++
+
+		if nBitsRead < 12 {
+			if bit&1 == 0 {
+				continue
+			}
+		} else if bit&1 != 0 {
+			return nil
+		}
+
+		// Unread the bits we've read, then return errMissingEOL.
+		b.bits = (b.bits >> nBitsRead) | bitsRead
+		b.nBits += nBitsRead
+		return errMissingEOL
+	}
+}
+
+type reader struct {
+	br        bitReader
+	subFormat SubFormat
+
+	// width is the image width in pixels.
+	width int
+
+	// rowsRemaining starts at the image height in pixels, when the reader is
+	// driven through the io.Reader interface, and decrements to zero as rows
+	// are decoded. Alternatively, it may be negative if the image height is
+	// not known in advance at the time of the NewReader call.
+	//
+	// When driven through DecodeIntoGray, this field is unused.
+	rowsRemaining int
+
+	// curr and prev hold the current and previous rows. Each element is either
+	// 0x00 (black) or 0xFF (white).
+	//
+	// prev may be nil, when processing the first row.
+	curr []byte
+	prev []byte
+
+	// ri is the read index. curr[:ri] are those bytes of curr that have been
+	// passed along via the Read method.
+	//
+	// When the reader is driven through DecodeIntoGray, instead of through the
+	// io.Reader interface, this field is unused.
+	ri int
+
+	// wi is the write index. curr[:wi] are those bytes of curr that have
+	// already been decoded via the decodeRow method.
+	//
+	// What this implementation calls wi is roughly equivalent to what the spec
+	// calls the a0 index.
+	wi int
+
+	// These fields are copied from the *Options (which may be nil).
+	align  bool
+	invert bool
+
+	// atStartOfRow is whether we have just started the row. Some parts of the
+	// spec say to treat this situation as if "wi = -1".
+	atStartOfRow bool
+
+	// penColorIsWhite is whether the next run is black or white.
+	penColorIsWhite bool
+
+	// seenStartOfImage is whether we've called the startDecode method.
+	seenStartOfImage bool
+
+	// truncated is whether the input is missing the final 6 consecutive EOL's
+	// (for Group3) or 2 consecutive EOL's (for Group4). Omitting that trailer
+	// (but otherwise padding to a byte boundary, with either all 0 bits or all
+	// 1 bits) is invalid according to the spec, but happens in practice when
+	// exporting from Adobe Acrobat to TIFF + CCITT. This package silently
+	// ignores the format error for CCITT input that has been truncated in that
+	// fashion, returning the full decoded image.
+	//
+	// Detecting trailer truncation (just after the final row of pixels)
+	// requires knowing which row is the final row, and therefore does not
+	// trigger if the image height is not known in advance.
+	truncated bool
+
+	// readErr is a sticky error for the Read method.
+	readErr error
+}
+
+func (z *reader) Read(p []byte) (int, error) {
+	if z.readErr != nil {
+		return 0, z.readErr
+	}
+	originalP := p
+
+	for len(p) > 0 {
+		// Allocate buffers (and decode any start-of-image codes), if
+		// processing the first or second row.
+		if z.curr == nil {
+			if !z.seenStartOfImage {
+				if z.readErr = z.startDecode(); z.readErr != nil {
+					break
+				}
+				z.atStartOfRow = true
+			}
+			z.curr = make([]byte, z.width)
+		}
+
+		// Decode the next row, if necessary.
+		if z.atStartOfRow {
+			if z.rowsRemaining < 0 {
+				// We do not know the image height in advance. See if the next
+				// code is an EOL. If it is, it is consumed. If it isn't, the
+				// bitReader shouldn't advance along the bit stream, and we
+				// simply decode another row of pixel data.
+				//
+				// For the Group4 subFormat, we may need to align to a byte
+				// boundary. For the Group3 subFormat, the previous z.decodeRow
+				// call (or z.startDecode call) has already consumed one of the
+				// 6 consecutive EOL's. The next EOL is actually the second of
+				// 6, in the middle, and we shouldn't align at that point.
+				if z.align && (z.subFormat == Group4) {
+					z.br.alignToByteBoundary()
+				}
+
+				if err := z.decodeEOL(); err == errMissingEOL {
+					// No-op. It's another row of pixel data.
+				} else if err != nil {
+					z.readErr = err
+					break
+				} else {
+					if z.readErr = z.finishDecode(true); z.readErr != nil {
+						break
+					}
+					z.readErr = io.EOF
+					break
+				}
+
+			} else if z.rowsRemaining == 0 {
+				// We do know the image height in advance, and we have already
+				// decoded exactly that many rows.
+				if z.readErr = z.finishDecode(false); z.readErr != nil {
+					break
+				}
+				z.readErr = io.EOF
+				break
+
+			} else {
+				z.rowsRemaining--
+			}
+
+			if z.readErr = z.decodeRow(z.rowsRemaining == 0); z.readErr != nil {
+				break
+			}
+		}
+
+		// Pack from z.curr (1 byte per pixel) to p (1 bit per pixel).
+		packD, packS := highBits(p, z.curr[z.ri:], z.invert)
+		p = p[packD:]
+		z.ri += packS
+
+		// Prepare to decode the next row, if necessary.
+		if z.ri == len(z.curr) {
+			z.ri, z.curr, z.prev = 0, z.prev, z.curr
+			z.atStartOfRow = true
+		}
+	}
+
+	n := len(originalP) - len(p)
+	if z.invert {
+		invertBytes(originalP[:n])
+	}
+	return n, z.readErr
+}
+
+func (z *reader) penColor() byte {
+	if z.penColorIsWhite {
+		return 0xFF
+	}
+	return 0x00
+}
+
+func (z *reader) startDecode() error {
+	switch z.subFormat {
+	case Group3:
+		if err := z.decodeEOL(); err != nil {
+			return err
+		}
+
+	case Group4:
+		// No-op.
+
+	default:
+		return errUnsupportedSubFormat
+	}
+
+	z.seenStartOfImage = true
+	return nil
+}
+
+func (z *reader) finishDecode(alreadySeenEOL bool) error {
+	numberOfEOLs := 0
+	switch z.subFormat {
+	case Group3:
+		if z.truncated {
+			return nil
+		}
+		// The stream ends with a RTC (Return To Control) of 6 consecutive
+		// EOL's, but we should have already just seen an EOL, either in
+		// z.startDecode (for a zero-height image) or in z.decodeRow.
+		numberOfEOLs = 5
+
+	case Group4:
+		autoDetectHeight := z.rowsRemaining < 0
+		if autoDetectHeight {
+			// Aligning to a byte boundary was already handled by reader.Read.
+		} else if z.align {
+			z.br.alignToByteBoundary()
+		}
+		// The stream ends with two EOL's. If the first one is missing, and we
+		// had an explicit image height, we just assume that the trailing two
+		// EOL's were truncated and return a nil error.
+		if err := z.decodeEOL(); err != nil {
+			if (err == errMissingEOL) && !autoDetectHeight {
+				z.truncated = true
+				return nil
+			}
+			return err
+		}
+		numberOfEOLs = 1
+
+	default:
+		return errUnsupportedSubFormat
+	}
+
+	if alreadySeenEOL {
+		numberOfEOLs--
+	}
+	for ; numberOfEOLs > 0; numberOfEOLs-- {
+		if err := z.decodeEOL(); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+func (z *reader) decodeEOL() error {
+	return decodeEOL(&z.br)
+}
+
+func (z *reader) decodeRow(finalRow bool) error {
+	z.wi = 0
+	z.atStartOfRow = true
+	z.penColorIsWhite = true
+
+	if z.align {
+		z.br.alignToByteBoundary()
+	}
+
+	switch z.subFormat {
+	case Group3:
+		for ; z.wi < len(z.curr); z.atStartOfRow = false {
+			if err := z.decodeRun(); err != nil {
+				return err
+			}
+		}
+		err := z.decodeEOL()
+		if finalRow && (err == errMissingEOL) {
+			z.truncated = true
+			return nil
+		}
+		return err
+
+	case Group4:
+		for ; z.wi < len(z.curr); z.atStartOfRow = false {
+			mode, err := decode(&z.br, modeDecodeTable[:])
+			if err != nil {
+				return err
+			}
+			rm := readerMode{}
+			if mode < uint32(len(readerModes)) {
+				rm = readerModes[mode]
+			}
+			if rm.function == nil {
+				return errInvalidMode
+			}
+			if err := rm.function(z, rm.arg); err != nil {
+				return err
+			}
+		}
+		return nil
+	}
+
+	return errUnsupportedSubFormat
+}
+
+func (z *reader) decodeRun() error {
+	table := blackDecodeTable[:]
+	if z.penColorIsWhite {
+		table = whiteDecodeTable[:]
+	}
+
+	total := 0
+	for {
+		n, err := decode(&z.br, table)
+		if err != nil {
+			return err
+		}
+		if n > maxWidth {
+			panic("unreachable")
+		}
+		total += int(n)
+		if total > maxWidth {
+			return errRunLengthTooLong
+		}
+		// Anything 0x3F or below is a terminal code.
+		if n <= 0x3F {
+			break
+		}
+	}
+
+	if total > (len(z.curr) - z.wi) {
+		return errRunLengthOverflowsWidth
+	}
+	dst := z.curr[z.wi : z.wi+total]
+	penColor := z.penColor()
+	for i := range dst {
+		dst[i] = penColor
+	}
+	z.wi += total
+	z.penColorIsWhite = !z.penColorIsWhite
+
+	return nil
+}
+
+// The various modes' semantics are based on determining a row of pixels'
+// "changing elements": those pixels whose color differs from the one on its
+// immediate left.
+//
+// The row above the first row is implicitly all white. Similarly, the column
+// to the left of the first column is implicitly all white.
+//
+// For example, here's Figure 1 in "ITU-T Recommendation T.6", where the
+// current and previous rows contain black (B) and white (w) pixels. The a?
+// indexes point into curr, the b? indexes point into prev.
+//
+//                 b1 b2
+//                 v  v
+// prev: BBBBBwwwwwBBBwwwww
+// curr: BBBwwwwwBBBBBBwwww
+//          ^    ^     ^
+//          a0   a1    a2
+//
+// a0 is the "reference element" or current decoder position, roughly
+// equivalent to what this implementation calls reader.wi.
+//
+// a1 is the next changing element to the right of a0, on the "coding line"
+// (the current row).
+//
+// a2 is the next changing element to the right of a1, again on curr.
+//
+// b1 is the first changing element on the "reference line" (the previous row)
+// to the right of a0 and of opposite color to a0.
+//
+// b2 is the next changing element to the right of b1, again on prev.
+//
+// The various modes calculate a1 (and a2, for modeH):
+//  - modePass calculates that a1 is at or to the right of b2.
+//  - modeH    calculates a1 and a2 without considering b1 or b2.
+//  - modeV*   calculates a1 to be b1 plus an adjustment (between -3 and +3).
+
+const (
+	findB1 = false
+	findB2 = true
+)
+
+// findB finds either the b1 or b2 value.
+func (z *reader) findB(whichB bool) int {
+	// The initial row is a special case. The previous row is implicitly all
+	// white, so that there are no changing pixel elements. We return b1 or b2
+	// to be at the end of the row.
+	if len(z.prev) != len(z.curr) {
+		return len(z.curr)
+	}
+
+	i := z.wi
+
+	if z.atStartOfRow {
+		// a0 is implicitly at -1, on a white pixel. b1 is the first black
+		// pixel in the previous row. b2 is the first white pixel after that.
+		for ; (i < len(z.prev)) && (z.prev[i] == 0xFF); i++ {
+		}
+		if whichB == findB2 {
+			for ; (i < len(z.prev)) && (z.prev[i] == 0x00); i++ {
+			}
+		}
+		return i
+	}
+
+	// As per figure 1 above, assume that the current pen color is white.
+	// First, walk past every contiguous black pixel in prev, starting at a0.
+	oppositeColor := ^z.penColor()
+	for ; (i < len(z.prev)) && (z.prev[i] == oppositeColor); i++ {
+	}
+
+	// Then walk past every contiguous white pixel.
+	penColor := ^oppositeColor
+	for ; (i < len(z.prev)) && (z.prev[i] == penColor); i++ {
+	}
+
+	// We're now at a black pixel (or at the end of the row). That's b1.
+	if whichB == findB2 {
+		// If we're looking for b2, walk past every contiguous black pixel
+		// again.
+		oppositeColor := ^penColor
+		for ; (i < len(z.prev)) && (z.prev[i] == oppositeColor); i++ {
+		}
+	}
+
+	return i
+}
+
+type readerMode struct {
+	function func(z *reader, arg int) error
+	arg      int
+}
+
+var readerModes = [...]readerMode{
+	modePass: {function: readerModePass},
+	modeH:    {function: readerModeH},
+	modeV0:   {function: readerModeV, arg: +0},
+	modeVR1:  {function: readerModeV, arg: +1},
+	modeVR2:  {function: readerModeV, arg: +2},
+	modeVR3:  {function: readerModeV, arg: +3},
+	modeVL1:  {function: readerModeV, arg: -1},
+	modeVL2:  {function: readerModeV, arg: -2},
+	modeVL3:  {function: readerModeV, arg: -3},
+	modeExt:  {function: readerModeExt},
+}
+
+func readerModePass(z *reader, arg int) error {
+	b2 := z.findB(findB2)
+	if (b2 < z.wi) || (len(z.curr) < b2) {
+		return errInvalidOffset
+	}
+	dst := z.curr[z.wi:b2]
+	penColor := z.penColor()
+	for i := range dst {
+		dst[i] = penColor
+	}
+	z.wi = b2
+	return nil
+}
+
+func readerModeH(z *reader, arg int) error {
+	// The first iteration finds a1. The second finds a2.
+	for i := 0; i < 2; i++ {
+		if err := z.decodeRun(); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+func readerModeV(z *reader, arg int) error {
+	a1 := z.findB(findB1) + arg
+	if (a1 < z.wi) || (len(z.curr) < a1) {
+		return errInvalidOffset
+	}
+	dst := z.curr[z.wi:a1]
+	penColor := z.penColor()
+	for i := range dst {
+		dst[i] = penColor
+	}
+	z.wi = a1
+	z.penColorIsWhite = !z.penColorIsWhite
+	return nil
+}
+
+func readerModeExt(z *reader, arg int) error {
+	return errUnsupportedMode
+}
+
+// DecodeIntoGray decodes the CCITT-formatted data in r into dst.
+//
+// It returns an error if dst's width and height don't match the implied width
+// and height of CCITT-formatted data.
+func DecodeIntoGray(dst *image.Gray, r io.Reader, order Order, sf SubFormat, opts *Options) error {
+	bounds := dst.Bounds()
+	if (bounds.Dx() < 0) || (bounds.Dy() < 0) {
+		return errInvalidBounds
+	}
+	if bounds.Dx() > maxWidth {
+		return errUnsupportedWidth
+	}
+
+	z := reader{
+		br:        bitReader{r: r, order: order},
+		subFormat: sf,
+		align:     (opts != nil) && opts.Align,
+		invert:    (opts != nil) && opts.Invert,
+		width:     bounds.Dx(),
+	}
+	if err := z.startDecode(); err != nil {
+		return err
+	}
+
+	width := bounds.Dx()
+	for y := bounds.Min.Y; y < bounds.Max.Y; y++ {
+		p := (y - bounds.Min.Y) * dst.Stride
+		z.curr = dst.Pix[p : p+width]
+		if err := z.decodeRow(y+1 == bounds.Max.Y); err != nil {
+			return err
+		}
+		z.curr, z.prev = nil, z.curr
+	}
+
+	if err := z.finishDecode(false); err != nil {
+		return err
+	}
+
+	if z.invert {
+		for y := bounds.Min.Y; y < bounds.Max.Y; y++ {
+			p := (y - bounds.Min.Y) * dst.Stride
+			invertBytes(dst.Pix[p : p+width])
+		}
+	}
+
+	return nil
+}
+
+// NewReader returns an io.Reader that decodes the CCITT-formatted data in r.
+// The resultant byte stream is one bit per pixel (MSB first), with 1 meaning
+// white and 0 meaning black. Each row in the result is byte-aligned.
+//
+// A negative height, such as passing AutoDetectHeight, means that the image
+// height is not known in advance. A negative width is invalid.
+func NewReader(r io.Reader, order Order, sf SubFormat, width int, height int, opts *Options) io.Reader {
+	readErr := error(nil)
+	if width < 0 {
+		readErr = errInvalidBounds
+	} else if width > maxWidth {
+		readErr = errUnsupportedWidth
+	}
+
+	return &reader{
+		br:            bitReader{r: r, order: order},
+		subFormat:     sf,
+		align:         (opts != nil) && opts.Align,
+		invert:        (opts != nil) && opts.Invert,
+		width:         width,
+		rowsRemaining: height,
+		readErr:       readErr,
+	}
+}