1// Copyright 2011 The Go Authors. All rights reserved. 2// Use of this source code is governed by a BSD-style 3// license that can be found in the LICENSE file. 4 5/* 6Package qr encodes QR codes. 7*/ 8package qr 9 10import ( 11 "errors" 12 "image" 13 "image/color" 14 15 "rsc.io/qr/coding" 16) 17 18// A Level denotes a QR error correction level. 19// From least to most tolerant of errors, they are L, M, Q, H. 20type Level int 21 22const ( 23 L Level = iota // 20% redundant 24 M // 38% redundant 25 Q // 55% redundant 26 H // 65% redundant 27) 28 29// Encode returns an encoding of text at the given error correction level. 30func Encode(text string, level Level) (*Code, error) { 31 // Pick data encoding, smallest first. 32 // We could split the string and use different encodings 33 // but that seems like overkill for now. 34 var enc coding.Encoding 35 switch { 36 case coding.Num(text).Check() == nil: 37 enc = coding.Num(text) 38 case coding.Alpha(text).Check() == nil: 39 enc = coding.Alpha(text) 40 default: 41 enc = coding.String(text) 42 } 43 44 // Pick size. 45 l := coding.Level(level) 46 var v coding.Version 47 for v = coding.MinVersion; ; v++ { 48 if v > coding.MaxVersion { 49 return nil, errors.New("text too long to encode as QR") 50 } 51 if enc.Bits(v) <= v.DataBytes(l)*8 { 52 break 53 } 54 } 55 56 // Build and execute plan. 57 p, err := coding.NewPlan(v, l, 0) 58 if err != nil { 59 return nil, err 60 } 61 cc, err := p.Encode(enc) 62 if err != nil { 63 return nil, err 64 } 65 66 // TODO: Pick appropriate mask. 67 68 return &Code{cc.Bitmap, cc.Size, cc.Stride, 8}, nil 69} 70 71// A Code is a square pixel grid. 72// It implements image.Image and direct PNG encoding. 73type Code struct { 74 Bitmap []byte // 1 is black, 0 is white 75 Size int // number of pixels on a side 76 Stride int // number of bytes per row 77 Scale int // number of image pixels per QR pixel 78} 79 80// Black returns true if the pixel at (x,y) is black. 81func (c *Code) Black(x, y int) bool { 82 return 0 <= x && x < c.Size && 0 <= y && y < c.Size && 83 c.Bitmap[y*c.Stride+x/8]&(1<<uint(7-x&7)) != 0 84} 85 86// Image returns an Image displaying the code. 87func (c *Code) Image() image.Image { 88 return &codeImage{c} 89 90} 91 92// codeImage implements image.Image 93type codeImage struct { 94 *Code 95} 96 97var ( 98 whiteColor color.Color = color.Gray{0xFF} 99 blackColor color.Color = color.Gray{0x00} 100) 101 102func (c *codeImage) Bounds() image.Rectangle { 103 d := (c.Size + 8) * c.Scale 104 return image.Rect(0, 0, d, d) 105} 106 107func (c *codeImage) At(x, y int) color.Color { 108 if c.Black(x, y) { 109 return blackColor 110 } 111 return whiteColor 112} 113 114func (c *codeImage) ColorModel() color.Model { 115 return color.GrayModel 116} 117