diff options
Diffstat (limited to 'vendor/rsc.io/qr/png.go')
| -rw-r--r-- | vendor/rsc.io/qr/png.go | 400 |
1 files changed, 400 insertions, 0 deletions
diff --git a/vendor/rsc.io/qr/png.go b/vendor/rsc.io/qr/png.go new file mode 100644 index 00000000..db49d057 --- /dev/null +++ b/vendor/rsc.io/qr/png.go @@ -0,0 +1,400 @@ +// 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) } |