package qr import ( "errors" "image" "image/color" "github.com/vitrun/qart/coding" ) // A Level denotes a QR error correction level. // From least to most tolerant of errors, they are L, M, Q, H. type Level int const ( L Level = iota // 20% redundant M // 38% redundant Q // 55% redundant H // 65% redundant ) // 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 } // A Code is a square pixel grid. // It implements image.Image and direct PNG encoding. type Code struct { Bitmap []byte // 1 is black, 0 is white Size int // number of pixels on a side Stride int // number of bytes per row Scale int // number of image pixels per QR pixel } // Black returns true if the pixel at (x,y) is black. func (c *Code) Black(x, y int) bool { return 0 <= x && x < c.Size && 0 <= y && y < c.Size && c.Bitmap[y*c.Stride+x/8]&(1<