mirror of
https://github.com/cwinfo/matterbridge.git
synced 2024-11-27 03:11:36 +00:00
401 lines
8.5 KiB
Go
401 lines
8.5 KiB
Go
// 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 qr
|
|
|
|
// PNG writer for QR codes.
|
|
|
|
import (
|
|
"bytes"
|
|
"encoding/binary"
|
|
"hash"
|
|
"hash/crc32"
|
|
)
|
|
|
|
// PNG returns a PNG image displaying the code.
|
|
//
|
|
// PNG uses a custom encoder tailored to QR codes.
|
|
// Its compressed size is about 2x away from optimal,
|
|
// but it runs about 20x faster than calling png.Encode
|
|
// on c.Image().
|
|
func (c *Code) PNG() []byte {
|
|
var p pngWriter
|
|
return p.encode(c)
|
|
}
|
|
|
|
type pngWriter struct {
|
|
tmp [16]byte
|
|
wctmp [4]byte
|
|
buf bytes.Buffer
|
|
zlib bitWriter
|
|
crc hash.Hash32
|
|
}
|
|
|
|
var pngHeader = []byte("\x89PNG\r\n\x1a\n")
|
|
|
|
func (w *pngWriter) encode(c *Code) []byte {
|
|
scale := c.Scale
|
|
siz := c.Size
|
|
|
|
w.buf.Reset()
|
|
|
|
// Header
|
|
w.buf.Write(pngHeader)
|
|
|
|
// Header block
|
|
binary.BigEndian.PutUint32(w.tmp[0:4], uint32((siz+8)*scale))
|
|
binary.BigEndian.PutUint32(w.tmp[4:8], uint32((siz+8)*scale))
|
|
w.tmp[8] = 1 // 1-bit
|
|
w.tmp[9] = 0 // gray
|
|
w.tmp[10] = 0
|
|
w.tmp[11] = 0
|
|
w.tmp[12] = 0
|
|
w.writeChunk("IHDR", w.tmp[:13])
|
|
|
|
// Comment
|
|
w.writeChunk("tEXt", comment)
|
|
|
|
// Data
|
|
w.zlib.writeCode(c)
|
|
w.writeChunk("IDAT", w.zlib.bytes.Bytes())
|
|
|
|
// End
|
|
w.writeChunk("IEND", nil)
|
|
|
|
return w.buf.Bytes()
|
|
}
|
|
|
|
var comment = []byte("Software\x00QR-PNG http://qr.swtch.com/")
|
|
|
|
func (w *pngWriter) writeChunk(name string, data []byte) {
|
|
if w.crc == nil {
|
|
w.crc = crc32.NewIEEE()
|
|
}
|
|
binary.BigEndian.PutUint32(w.wctmp[0:4], uint32(len(data)))
|
|
w.buf.Write(w.wctmp[0:4])
|
|
w.crc.Reset()
|
|
copy(w.wctmp[0:4], name)
|
|
w.buf.Write(w.wctmp[0:4])
|
|
w.crc.Write(w.wctmp[0:4])
|
|
w.buf.Write(data)
|
|
w.crc.Write(data)
|
|
crc := w.crc.Sum32()
|
|
binary.BigEndian.PutUint32(w.wctmp[0:4], crc)
|
|
w.buf.Write(w.wctmp[0:4])
|
|
}
|
|
|
|
func (b *bitWriter) writeCode(c *Code) {
|
|
const ftNone = 0
|
|
|
|
b.adler32.Reset()
|
|
b.bytes.Reset()
|
|
b.nbit = 0
|
|
|
|
scale := c.Scale
|
|
siz := c.Size
|
|
|
|
// zlib header
|
|
b.tmp[0] = 0x78
|
|
b.tmp[1] = 0
|
|
b.tmp[1] += uint8(31 - (uint16(b.tmp[0])<<8+uint16(b.tmp[1]))%31)
|
|
b.bytes.Write(b.tmp[0:2])
|
|
|
|
// Start flate block.
|
|
b.writeBits(1, 1, false) // final block
|
|
b.writeBits(1, 2, false) // compressed, fixed Huffman tables
|
|
|
|
// White border.
|
|
// First row.
|
|
b.byte(ftNone)
|
|
n := (scale*(siz+8) + 7) / 8
|
|
b.byte(255)
|
|
b.repeat(n-1, 1)
|
|
// 4*scale rows total.
|
|
b.repeat((4*scale-1)*(1+n), 1+n)
|
|
|
|
for i := 0; i < 4*scale; i++ {
|
|
b.adler32.WriteNByte(ftNone, 1)
|
|
b.adler32.WriteNByte(255, n)
|
|
}
|
|
|
|
row := make([]byte, 1+n)
|
|
for y := 0; y < siz; y++ {
|
|
row[0] = ftNone
|
|
j := 1
|
|
var z uint8
|
|
nz := 0
|
|
for x := -4; x < siz+4; x++ {
|
|
// Raw data.
|
|
for i := 0; i < scale; i++ {
|
|
z <<= 1
|
|
if !c.Black(x, y) {
|
|
z |= 1
|
|
}
|
|
if nz++; nz == 8 {
|
|
row[j] = z
|
|
j++
|
|
nz = 0
|
|
}
|
|
}
|
|
}
|
|
if j < len(row) {
|
|
row[j] = z
|
|
}
|
|
for _, z := range row {
|
|
b.byte(z)
|
|
}
|
|
|
|
// Scale-1 copies.
|
|
b.repeat((scale-1)*(1+n), 1+n)
|
|
|
|
b.adler32.WriteN(row, scale)
|
|
}
|
|
|
|
// White border.
|
|
// First row.
|
|
b.byte(ftNone)
|
|
b.byte(255)
|
|
b.repeat(n-1, 1)
|
|
// 4*scale rows total.
|
|
b.repeat((4*scale-1)*(1+n), 1+n)
|
|
|
|
for i := 0; i < 4*scale; i++ {
|
|
b.adler32.WriteNByte(ftNone, 1)
|
|
b.adler32.WriteNByte(255, n)
|
|
}
|
|
|
|
// End of block.
|
|
b.hcode(256)
|
|
b.flushBits()
|
|
|
|
// adler32
|
|
binary.BigEndian.PutUint32(b.tmp[0:], b.adler32.Sum32())
|
|
b.bytes.Write(b.tmp[0:4])
|
|
}
|
|
|
|
// A bitWriter is a write buffer for bit-oriented data like deflate.
|
|
type bitWriter struct {
|
|
bytes bytes.Buffer
|
|
bit uint32
|
|
nbit uint
|
|
|
|
tmp [4]byte
|
|
adler32 adigest
|
|
}
|
|
|
|
func (b *bitWriter) writeBits(bit uint32, nbit uint, rev bool) {
|
|
// reverse, for huffman codes
|
|
if rev {
|
|
br := uint32(0)
|
|
for i := uint(0); i < nbit; i++ {
|
|
br |= ((bit >> i) & 1) << (nbit - 1 - i)
|
|
}
|
|
bit = br
|
|
}
|
|
b.bit |= bit << b.nbit
|
|
b.nbit += nbit
|
|
for b.nbit >= 8 {
|
|
b.bytes.WriteByte(byte(b.bit))
|
|
b.bit >>= 8
|
|
b.nbit -= 8
|
|
}
|
|
}
|
|
|
|
func (b *bitWriter) flushBits() {
|
|
if b.nbit > 0 {
|
|
b.bytes.WriteByte(byte(b.bit))
|
|
b.nbit = 0
|
|
b.bit = 0
|
|
}
|
|
}
|
|
|
|
func (b *bitWriter) hcode(v int) {
|
|
/*
|
|
Lit Value Bits Codes
|
|
--------- ---- -----
|
|
0 - 143 8 00110000 through
|
|
10111111
|
|
144 - 255 9 110010000 through
|
|
111111111
|
|
256 - 279 7 0000000 through
|
|
0010111
|
|
280 - 287 8 11000000 through
|
|
11000111
|
|
*/
|
|
switch {
|
|
case v <= 143:
|
|
b.writeBits(uint32(v)+0x30, 8, true)
|
|
case v <= 255:
|
|
b.writeBits(uint32(v-144)+0x190, 9, true)
|
|
case v <= 279:
|
|
b.writeBits(uint32(v-256)+0, 7, true)
|
|
case v <= 287:
|
|
b.writeBits(uint32(v-280)+0xc0, 8, true)
|
|
default:
|
|
panic("invalid hcode")
|
|
}
|
|
}
|
|
|
|
func (b *bitWriter) byte(x byte) {
|
|
b.hcode(int(x))
|
|
}
|
|
|
|
func (b *bitWriter) codex(c int, val int, nx uint) {
|
|
b.hcode(c + val>>nx)
|
|
b.writeBits(uint32(val)&(1<<nx-1), nx, false)
|
|
}
|
|
|
|
func (b *bitWriter) repeat(n, d int) {
|
|
for ; n >= 258+3; n -= 258 {
|
|
b.repeat1(258, d)
|
|
}
|
|
if n > 258 {
|
|
// 258 < n < 258+3
|
|
b.repeat1(10, d)
|
|
b.repeat1(n-10, d)
|
|
return
|
|
}
|
|
if n < 3 {
|
|
panic("invalid flate repeat")
|
|
}
|
|
b.repeat1(n, d)
|
|
}
|
|
|
|
func (b *bitWriter) repeat1(n, d int) {
|
|
/*
|
|
Extra Extra Extra
|
|
Code Bits Length(s) Code Bits Lengths Code Bits Length(s)
|
|
---- ---- ------ ---- ---- ------- ---- ---- -------
|
|
257 0 3 267 1 15,16 277 4 67-82
|
|
258 0 4 268 1 17,18 278 4 83-98
|
|
259 0 5 269 2 19-22 279 4 99-114
|
|
260 0 6 270 2 23-26 280 4 115-130
|
|
261 0 7 271 2 27-30 281 5 131-162
|
|
262 0 8 272 2 31-34 282 5 163-194
|
|
263 0 9 273 3 35-42 283 5 195-226
|
|
264 0 10 274 3 43-50 284 5 227-257
|
|
265 1 11,12 275 3 51-58 285 0 258
|
|
266 1 13,14 276 3 59-66
|
|
*/
|
|
switch {
|
|
case n <= 10:
|
|
b.codex(257, n-3, 0)
|
|
case n <= 18:
|
|
b.codex(265, n-11, 1)
|
|
case n <= 34:
|
|
b.codex(269, n-19, 2)
|
|
case n <= 66:
|
|
b.codex(273, n-35, 3)
|
|
case n <= 130:
|
|
b.codex(277, n-67, 4)
|
|
case n <= 257:
|
|
b.codex(281, n-131, 5)
|
|
case n == 258:
|
|
b.hcode(285)
|
|
default:
|
|
panic("invalid repeat length")
|
|
}
|
|
|
|
/*
|
|
Extra Extra Extra
|
|
Code Bits Dist Code Bits Dist Code Bits Distance
|
|
---- ---- ---- ---- ---- ------ ---- ---- --------
|
|
0 0 1 10 4 33-48 20 9 1025-1536
|
|
1 0 2 11 4 49-64 21 9 1537-2048
|
|
2 0 3 12 5 65-96 22 10 2049-3072
|
|
3 0 4 13 5 97-128 23 10 3073-4096
|
|
4 1 5,6 14 6 129-192 24 11 4097-6144
|
|
5 1 7,8 15 6 193-256 25 11 6145-8192
|
|
6 2 9-12 16 7 257-384 26 12 8193-12288
|
|
7 2 13-16 17 7 385-512 27 12 12289-16384
|
|
8 3 17-24 18 8 513-768 28 13 16385-24576
|
|
9 3 25-32 19 8 769-1024 29 13 24577-32768
|
|
*/
|
|
if d <= 4 {
|
|
b.writeBits(uint32(d-1), 5, true)
|
|
} else if d <= 32768 {
|
|
nbit := uint(16)
|
|
for d <= 1<<(nbit-1) {
|
|
nbit--
|
|
}
|
|
v := uint32(d - 1)
|
|
v &^= 1 << (nbit - 1) // top bit is implicit
|
|
code := uint32(2*nbit - 2) // second bit is low bit of code
|
|
code |= v >> (nbit - 2)
|
|
v &^= 1 << (nbit - 2)
|
|
b.writeBits(code, 5, true)
|
|
// rest of bits follow
|
|
b.writeBits(uint32(v), nbit-2, false)
|
|
} else {
|
|
panic("invalid repeat distance")
|
|
}
|
|
}
|
|
|
|
func (b *bitWriter) run(v byte, n int) {
|
|
if n == 0 {
|
|
return
|
|
}
|
|
b.byte(v)
|
|
if n-1 < 3 {
|
|
for i := 0; i < n-1; i++ {
|
|
b.byte(v)
|
|
}
|
|
} else {
|
|
b.repeat(n-1, 1)
|
|
}
|
|
}
|
|
|
|
type adigest struct {
|
|
a, b uint32
|
|
}
|
|
|
|
func (d *adigest) Reset() { d.a, d.b = 1, 0 }
|
|
|
|
const amod = 65521
|
|
|
|
func aupdate(a, b uint32, pi byte, n int) (aa, bb uint32) {
|
|
// TODO(rsc): 6g doesn't do magic multiplies for b %= amod,
|
|
// only for b = b%amod.
|
|
|
|
// invariant: a, b < amod
|
|
if pi == 0 {
|
|
b += uint32(n%amod) * a
|
|
b = b % amod
|
|
return a, b
|
|
}
|
|
|
|
// n times:
|
|
// a += pi
|
|
// b += a
|
|
// is same as
|
|
// b += n*a + n*(n+1)/2*pi
|
|
// a += n*pi
|
|
m := uint32(n)
|
|
b += (m % amod) * a
|
|
b = b % amod
|
|
b += (m * (m + 1) / 2) % amod * uint32(pi)
|
|
b = b % amod
|
|
a += (m % amod) * uint32(pi)
|
|
a = a % amod
|
|
return a, b
|
|
}
|
|
|
|
func afinish(a, b uint32) uint32 {
|
|
return b<<16 | a
|
|
}
|
|
|
|
func (d *adigest) WriteN(p []byte, n int) {
|
|
for i := 0; i < n; i++ {
|
|
for _, pi := range p {
|
|
d.a, d.b = aupdate(d.a, d.b, pi, 1)
|
|
}
|
|
}
|
|
}
|
|
|
|
func (d *adigest) WriteNByte(pi byte, n int) {
|
|
d.a, d.b = aupdate(d.a, d.b, pi, n)
|
|
}
|
|
|
|
func (d *adigest) Sum32() uint32 { return afinish(d.a, d.b) }
|