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310 lines
6.8 KiB
Go
310 lines
6.8 KiB
Go
// go-qrcode
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// Copyright 2014 Tom Harwood
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package qrcode
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// symbol is a 2D array of bits representing a QR Code symbol.
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//
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// A symbol consists of size*size modules, with each module normally drawn as a
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// black or white square. The symbol also has a border of quietZoneSize modules.
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//
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// A (fictional) size=2, quietZoneSize=1 QR Code looks like:
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//
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// +----+
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// | |
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// | ab |
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// | cd |
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// | |
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// +----+
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//
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// For ease of implementation, the functions to set/get bits ignore the border,
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// so (0,0)=a, (0,1)=b, (1,0)=c, and (1,1)=d. The entire symbol (including the
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// border) is returned by bitmap().
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//
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type symbol struct {
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// Value of module at [y][x]. True is set.
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module [][]bool
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// True if the module at [y][x] is used (to either true or false).
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// Used to identify unused modules.
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isUsed [][]bool
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// Combined width/height of the symbol and quiet zones.
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//
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// size = symbolSize + 2*quietZoneSize.
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size int
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// Width/height of the symbol only.
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symbolSize int
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// Width/height of a single quiet zone.
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quietZoneSize int
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}
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// newSymbol constructs a symbol of size size*size, with a border of
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// quietZoneSize.
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func newSymbol(size int, quietZoneSize int) *symbol {
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var m symbol
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m.module = make([][]bool, size+2*quietZoneSize)
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m.isUsed = make([][]bool, size+2*quietZoneSize)
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for i := range m.module {
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m.module[i] = make([]bool, size+2*quietZoneSize)
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m.isUsed[i] = make([]bool, size+2*quietZoneSize)
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}
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m.size = size + 2*quietZoneSize
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m.symbolSize = size
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m.quietZoneSize = quietZoneSize
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return &m
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}
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// get returns the module value at (x, y).
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func (m *symbol) get(x int, y int) (v bool) {
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v = m.module[y+m.quietZoneSize][x+m.quietZoneSize]
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return
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}
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// empty returns true if the module at (x, y) has not been set (to either true
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// or false).
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func (m *symbol) empty(x int, y int) bool {
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return !m.isUsed[y+m.quietZoneSize][x+m.quietZoneSize]
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}
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// numEmptyModules returns the number of empty modules.
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//
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// Initially numEmptyModules is symbolSize * symbolSize. After every module has
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// been set (to either true or false), the number of empty modules is zero.
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func (m *symbol) numEmptyModules() int {
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var count int
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for y := 0; y < m.symbolSize; y++ {
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for x := 0; x < m.symbolSize; x++ {
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if !m.isUsed[y+m.quietZoneSize][x+m.quietZoneSize] {
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count++
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}
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}
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}
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return count
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}
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// set sets the module at (x, y) to v.
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func (m *symbol) set(x int, y int, v bool) {
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m.module[y+m.quietZoneSize][x+m.quietZoneSize] = v
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m.isUsed[y+m.quietZoneSize][x+m.quietZoneSize] = true
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}
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// set2dPattern sets a 2D array of modules, starting at (x, y).
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func (m *symbol) set2dPattern(x int, y int, v [][]bool) {
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for j, row := range v {
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for i, value := range row {
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m.set(x+i, y+j, value)
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}
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}
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}
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// bitmap returns the entire symbol, including the quiet zone.
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func (m *symbol) bitmap() [][]bool {
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module := make([][]bool, len(m.module))
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for i := range m.module {
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module[i] = m.module[i][:]
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}
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return module
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}
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// string returns a pictorial representation of the symbol, suitable for
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// printing in a TTY.
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func (m *symbol) string() string {
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var result string
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for _, row := range m.module {
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for _, value := range row {
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switch value {
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case true:
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result += " "
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case false:
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// Unicode 'FULL BLOCK' (U+2588).
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result += "██"
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}
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}
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result += "\n"
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}
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return result
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}
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// Constants used to weight penalty calculations. Specified by ISO/IEC
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// 18004:2006.
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const (
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penaltyWeight1 = 3
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penaltyWeight2 = 3
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penaltyWeight3 = 40
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penaltyWeight4 = 10
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)
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// penaltyScore returns the penalty score of the symbol. The penalty score
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// consists of the sum of the four individual penalty types.
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func (m *symbol) penaltyScore() int {
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return m.penalty1() + m.penalty2() + m.penalty3() + m.penalty4()
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}
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// penalty1 returns the penalty score for "adjacent modules in row/column with
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// same colour".
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//
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// The numbers of adjacent matching modules and scores are:
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// 0-5: score = 0
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// 6+ : score = penaltyWeight1 + (numAdjacentModules - 5)
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func (m *symbol) penalty1() int {
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penalty := 0
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for x := 0; x < m.symbolSize; x++ {
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lastValue := m.get(x, 0)
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count := 1
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for y := 1; y < m.symbolSize; y++ {
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v := m.get(x, y)
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if v != lastValue {
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count = 1
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lastValue = v
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} else {
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count++
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if count == 6 {
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penalty += penaltyWeight1 + 1
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} else if count > 6 {
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penalty++
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}
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}
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}
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}
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for y := 0; y < m.symbolSize; y++ {
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lastValue := m.get(0, y)
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count := 1
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for x := 1; x < m.symbolSize; x++ {
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v := m.get(x, y)
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if v != lastValue {
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count = 1
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lastValue = v
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} else {
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count++
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if count == 6 {
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penalty += penaltyWeight1 + 1
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} else if count > 6 {
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penalty++
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}
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}
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}
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}
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return penalty
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}
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// penalty2 returns the penalty score for "block of modules in the same colour".
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//
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// m*n: score = penaltyWeight2 * (m-1) * (n-1).
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func (m *symbol) penalty2() int {
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penalty := 0
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for y := 1; y < m.symbolSize; y++ {
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for x := 1; x < m.symbolSize; x++ {
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topLeft := m.get(x-1, y-1)
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above := m.get(x, y-1)
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left := m.get(x-1, y)
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current := m.get(x, y)
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if current == left && current == above && current == topLeft {
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penalty++
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}
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}
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}
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return penalty * penaltyWeight2
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}
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// penalty3 returns the penalty score for "1:1:3:1:1 ratio
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// (dark:light:dark:light:dark) pattern in row/column, preceded or followed by
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// light area 4 modules wide".
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//
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// Existence of the pattern scores penaltyWeight3.
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func (m *symbol) penalty3() int {
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penalty := 0
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for y := 0; y < m.symbolSize; y++ {
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var bitBuffer int16 = 0x00
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for x := 0; x < m.symbolSize; x++ {
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bitBuffer <<= 1
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if v := m.get(x, y); v {
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bitBuffer |= 1
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}
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switch bitBuffer & 0x7ff {
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// 0b000 0101 1101 or 0b10111010000
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// 0x05d or 0x5d0
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case 0x05d, 0x5d0:
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penalty += penaltyWeight3
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bitBuffer = 0xFF
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default:
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if x == m.symbolSize-1 && (bitBuffer&0x7f) == 0x5d {
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penalty += penaltyWeight3
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bitBuffer = 0xFF
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}
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}
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}
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}
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for x := 0; x < m.symbolSize; x++ {
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var bitBuffer int16 = 0x00
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for y := 0; y < m.symbolSize; y++ {
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bitBuffer <<= 1
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if v := m.get(x, y); v {
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bitBuffer |= 1
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}
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switch bitBuffer & 0x7ff {
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// 0b000 0101 1101 or 0b10111010000
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// 0x05d or 0x5d0
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case 0x05d, 0x5d0:
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penalty += penaltyWeight3
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bitBuffer = 0xFF
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default:
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if y == m.symbolSize-1 && (bitBuffer&0x7f) == 0x5d {
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penalty += penaltyWeight3
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bitBuffer = 0xFF
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}
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}
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}
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}
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return penalty
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}
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// penalty4 returns the penalty score...
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func (m *symbol) penalty4() int {
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numModules := m.symbolSize * m.symbolSize
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numDarkModules := 0
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for x := 0; x < m.symbolSize; x++ {
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for y := 0; y < m.symbolSize; y++ {
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if v := m.get(x, y); v {
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numDarkModules++
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}
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}
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}
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numDarkModuleDeviation := numModules/2 - numDarkModules
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if numDarkModuleDeviation < 0 {
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numDarkModuleDeviation *= -1
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}
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return penaltyWeight4 * (numDarkModuleDeviation / (numModules / 20))
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}
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