// Encode encodes a string using the given version, level, and mask. func Encode(w http.ResponseWriter, req *http.Request) { val := func(s string) int { v, _ := strconv.Atoi(req.FormValue(s)) return v } l := coding.Level(val("l")) v := coding.Version(val("v")) enc := coding.String(req.FormValue("t")) m := coding.Mask(val("m")) p, err := coding.NewPlan(v, l, m) if err != nil { panic(err) } cc, err := p.Encode(enc) if err != nil { panic(err) } c := &qr.Code{Bitmap: cc.Bitmap, Size: cc.Size, Stride: cc.Stride, Scale: 8} w.Header().Set("Content-Type", "image/png") w.Header().Set("Cache-Control", "public, max-age=3600") w.Write(c.PNG()) }
// Encode returns an encoding of text at the given error correction level. func Encode(text string, level Level) (*Code, error) { // Pick data encoding, smallest first. // We could split the string and use different encodings // but that seems like overkill for now. var enc coding.Encoding switch { case coding.Num(text).Check() == nil: enc = coding.Num(text) case coding.Alpha(text).Check() == nil: enc = coding.Alpha(text) default: enc = coding.String(text) } // Pick size. l := coding.Level(level) var v coding.Version for v = coding.MinVersion; ; v++ { if v > coding.MaxVersion { return nil, errors.New("text too long to encode as QR") } if enc.Bits(v) <= v.DataBytes(l)*8 { break } } // Build and execute plan. p, err := coding.NewPlan(v, l, 0) if err != nil { return nil, err } cc, err := p.Encode(enc) if err != nil { return nil, err } // TODO: Pick appropriate mask. return &Code{cc.Bitmap, cc.Size, cc.Stride, 8}, nil }
func (m *Image) Encode(req *http.Request) error { p, err := coding.NewPlan(coding.Version(m.Version), coding.L, coding.Mask(m.Mask)) if err != nil { return err } m.rotate(p, m.Rotation) rand := rand.New(rand.NewSource(m.Seed)) // QR parameters. nd := p.DataBytes / p.Blocks nc := p.CheckBytes / p.Blocks extra := p.DataBytes - nd*p.Blocks rs := gf256.NewRSEncoder(coding.Field, nc) // Build information about pixels, indexed by data/check bit number. pixByOff := make([]Pixinfo, (p.DataBytes+p.CheckBytes)*8) expect := make([][]bool, len(p.Pixel)) for y, row := range p.Pixel { expect[y] = make([]bool, len(row)) for x, pix := range row { targ, contrast := m.target(x, y) if m.RandControl && contrast >= 0 { contrast = rand.Intn(128) + 64*((x+y)%2) + 64*((x+y)%3%2) } expect[y][x] = pix&coding.Black != 0 if r := pix.Role(); r == coding.Data || r == coding.Check { pixByOff[pix.Offset()] = Pixinfo{X: x, Y: y, Pix: pix, Targ: targ, Contrast: contrast} } } } Again: // Count fixed initial data bits, prepare template URL. url := m.URL + "#" var b coding.Bits coding.String(url).Encode(&b, p.Version) coding.Num("").Encode(&b, p.Version) bbit := b.Bits() dbit := p.DataBytes*8 - bbit if dbit < 0 { return fmt.Errorf("cannot encode URL into available bits") } num := make([]byte, dbit/10*3) for i := range num { num[i] = '0' } b.Pad(dbit) b.Reset() coding.String(url).Encode(&b, p.Version) coding.Num(num).Encode(&b, p.Version) b.AddCheckBytes(p.Version, p.Level) data := b.Bytes() doff := 0 // data offset coff := 0 // checksum offset mbit := bbit + dbit/10*10 // Choose pixels. bitblocks := make([]*BitBlock, p.Blocks) for blocknum := 0; blocknum < p.Blocks; blocknum++ { if blocknum == p.Blocks-extra { nd++ } bdata := data[doff/8 : doff/8+nd] cdata := data[p.DataBytes+coff/8 : p.DataBytes+coff/8+nc] bb := newBlock(nd, nc, rs, bdata, cdata) bitblocks[blocknum] = bb // Determine which bits in this block we can try to edit. lo, hi := 0, nd*8 if lo < bbit-doff { lo = bbit - doff if lo > hi { lo = hi } } if hi > mbit-doff { hi = mbit - doff if hi < lo { hi = lo } } // Preserve [0, lo) and [hi, nd*8). for i := 0; i < lo; i++ { if !bb.canSet(uint(i), (bdata[i/8]>>uint(7-i&7))&1) { return fmt.Errorf("cannot preserve required bits") } } for i := hi; i < nd*8; i++ { if !bb.canSet(uint(i), (bdata[i/8]>>uint(7-i&7))&1) { return fmt.Errorf("cannot preserve required bits") } } // Can edit [lo, hi) and checksum bits to hit target. // Determine which ones to try first. order := make([]Pixorder, (hi-lo)+nc*8) for i := lo; i < hi; i++ { order[i-lo].Off = doff + i } for i := 0; i < nc*8; i++ { order[hi-lo+i].Off = p.DataBytes*8 + coff + i } if m.OnlyDataBits { order = order[:hi-lo] } for i := range order { po := &order[i] po.Priority = pixByOff[po.Off].Contrast<<8 | rand.Intn(256) } sort.Sort(byPriority(order)) const mark = false for i := range order { po := &order[i] pinfo := &pixByOff[po.Off] bval := pinfo.Targ if bval < 128 { bval = 1 } else { bval = 0 } pix := pinfo.Pix if pix&coding.Invert != 0 { bval ^= 1 } if pinfo.HardZero { bval = 0 } var bi int if pix.Role() == coding.Data { bi = po.Off - doff } else { bi = po.Off - p.DataBytes*8 - coff + nd*8 } if bb.canSet(uint(bi), bval) { pinfo.Block = bb pinfo.Bit = uint(bi) if mark { p.Pixel[pinfo.Y][pinfo.X] = coding.Black } } else { if pinfo.HardZero { panic("hard zero") } if mark { p.Pixel[pinfo.Y][pinfo.X] = 0 } } } bb.copyOut() const cheat = false for i := 0; i < nd*8; i++ { pinfo := &pixByOff[doff+i] pix := p.Pixel[pinfo.Y][pinfo.X] if bb.B[i/8]&(1<<uint(7-i&7)) != 0 { pix ^= coding.Black } expect[pinfo.Y][pinfo.X] = pix&coding.Black != 0 if cheat { p.Pixel[pinfo.Y][pinfo.X] = pix & coding.Black } } for i := 0; i < nc*8; i++ { pinfo := &pixByOff[p.DataBytes*8+coff+i] pix := p.Pixel[pinfo.Y][pinfo.X] if bb.B[nd+i/8]&(1<<uint(7-i&7)) != 0 { pix ^= coding.Black } expect[pinfo.Y][pinfo.X] = pix&coding.Black != 0 if cheat { p.Pixel[pinfo.Y][pinfo.X] = pix & coding.Black } } doff += nd * 8 coff += nc * 8 } // Pass over all pixels again, dithering. if m.Dither { for i := range pixByOff { pinfo := &pixByOff[i] pinfo.DTarg = int(pinfo.Targ) } for y, row := range p.Pixel { for x, pix := range row { if pix.Role() != coding.Data && pix.Role() != coding.Check { continue } pinfo := &pixByOff[pix.Offset()] if pinfo.Block == nil { // did not choose this pixel continue } pix := pinfo.Pix pval := byte(1) // pixel value (black) v := 0 // gray value (black) targ := pinfo.DTarg if targ >= 128 { // want white pval = 0 v = 255 } bval := pval // bit value if pix&coding.Invert != 0 { bval ^= 1 } if pinfo.HardZero && bval != 0 { bval ^= 1 pval ^= 1 v ^= 255 } // Set pixel value as we want it. pinfo.Block.reset(pinfo.Bit, bval) _, _ = x, y err := targ - v if x+1 < len(row) { addDither(pixByOff, row[x+1], err*7/16) } if false && y+1 < len(p.Pixel) { if x > 0 { addDither(pixByOff, p.Pixel[y+1][x-1], err*3/16) } addDither(pixByOff, p.Pixel[y+1][x], err*5/16) if x+1 < len(row) { addDither(pixByOff, p.Pixel[y+1][x+1], err*1/16) } } } } for _, bb := range bitblocks { bb.copyOut() } } noops := 0 // Copy numbers back out. for i := 0; i < dbit/10; i++ { // Pull out 10 bits. v := 0 for j := 0; j < 10; j++ { bi := uint(bbit + 10*i + j) v <<= 1 v |= int((data[bi/8] >> (7 - bi&7)) & 1) } // Turn into 3 digits. if v >= 1000 { // Oops - too many 1 bits. // We know the 512, 256, 128, 64, 32 bits are all set. // Pick one at random to clear. This will break some // checksum bits, but so be it. println("oops", i, v) pinfo := &pixByOff[bbit+10*i+3] // TODO random pinfo.Contrast = 1e9 >> 8 pinfo.HardZero = true noops++ } num[i*3+0] = byte(v/100 + '0') num[i*3+1] = byte(v/10%10 + '0') num[i*3+2] = byte(v%10 + '0') } if noops > 0 { goto Again } var b1 coding.Bits coding.String(url).Encode(&b1, p.Version) coding.Num(num).Encode(&b1, p.Version) b1.AddCheckBytes(p.Version, p.Level) if !bytes.Equal(b.Bytes(), b1.Bytes()) { fmt.Printf("mismatch\n%d %x\n%d %x\n", len(b.Bytes()), b.Bytes(), len(b1.Bytes()), b1.Bytes()) panic("byte mismatch") } cc, err := p.Encode(coding.String(url), coding.Num(num)) if err != nil { return err } if !m.Dither { for y, row := range expect { for x, pix := range row { if cc.Black(x, y) != pix { println("mismatch", x, y, p.Pixel[y][x].String()) } } } } m.Code = &qr.Code{Bitmap: cc.Bitmap, Size: cc.Size, Stride: cc.Stride, Scale: m.Scale} if m.SaveControl { m.Control = pngEncode(makeImage(req, "", "", 0, cc.Size, 4, m.Scale, func(x, y int) (rgba uint32) { pix := p.Pixel[y][x] if pix.Role() == coding.Data || pix.Role() == coding.Check { pinfo := &pixByOff[pix.Offset()] if pinfo.Block != nil { if cc.Black(x, y) { return 0x000000ff } return 0xffffffff } } if cc.Black(x, y) { return 0x3f3f3fff } return 0xbfbfbfff })) } return nil }