Implemented drawing a border around QR code so that scanner apps can better detect QR code

EpcQrCode/src/commonMain/kotlin/net/codinux/banking/epcqrcode/EpcQrCode.kt

@@ -41,12 +41,12 @@ open class EpcQrCode(
   }
 
 
-  open fun qrCodeAsString(invertColors: Boolean = false): String {
+  open fun qrCodeAsString(border: Int = 0, invertColors: Boolean = false): String {
-    return EpcQrCodeStringFormatter().asString(this, invertColors)
+    return EpcQrCodeStringFormatter().asString(this, border, invertColors)
   }
 
-  open fun qrCodeAsSmallString(invertColors: Boolean = false): String {
+  open fun qrCodeAsSmallString(border: Int = 0, invertColors: Boolean = false): String {
-    return EpcQrCodeStringFormatter().asSmallString(this, invertColors)
+    return EpcQrCodeStringFormatter().asSmallString(this, border, invertColors)
   }
 
 

EpcQrCode/src/commonMain/kotlin/net/codinux/banking/epcqrcode/EpcQrCodeStringFormatter.kt

@@ -14,14 +14,18 @@ open class EpcQrCodeStringFormatter {
   }
 
 
-  open fun asString(epcQrCode: EpcQrCode, invertColors: Boolean = false): String {
+  open fun asString(epcQrCode: EpcQrCode, border: Int = 0, invertColors: Boolean = false): String {
     val bitIsSetColor = if (invertColors) BitIsNotSetColor + BitIsNotSetColor else BitIsSetColor + BitIsSetColor
     val bitIsNotSetColor = if (invertColors) BitIsSetColor + BitIsSetColor else BitIsNotSetColor + BitIsNotSetColor
     val height = epcQrCode.height
     val width = epcQrCode.width
     val string = StringBuilder(height * width)
 
+    printBorderAboveOrBelow(border, width, string, bitIsNotSetColor)
+
     for (y in 1 until height) {
+      printBorderBeforeOrAfter(border, string, bitIsNotSetColor)
+
       for (x in 1 until width) {
         if (isBitSet(epcQrCode, x, y)) {
           string.append(bitIsSetColor)
@@ -30,22 +34,30 @@ open class EpcQrCodeStringFormatter {
         }
       }
 
+      printBorderBeforeOrAfter(border, string, bitIsNotSetColor)
+
       string.appendLine()
     }
 
+    printBorderAboveOrBelow(border, width, string, bitIsNotSetColor)
+
     return string.toString()
   }
 
-  open fun asSmallString(epcQrCode: EpcQrCode, invertColors: Boolean = false): String {
+  open fun asSmallString(epcQrCode: EpcQrCode, border: Int = 0, invertColors: Boolean = false): String {
     val bitIsSetColor = if (invertColors) BitIsNotSetColor else BitIsSetColor
     val bitIsNotSetColor = if (invertColors) BitIsSetColor else BitIsNotSetColor
     val upperBitSetColor = if (invertColors) SmallSizeLowerBitSetColor else SmallSizeUpperBitSetColor
     val lowerBitSetColor = if (invertColors) SmallSizeUpperBitSetColor else SmallSizeLowerBitSetColor
     val height = epcQrCode.height
     val width = epcQrCode.width
-    val string = StringBuilder(height * width)
+    val string = StringBuilder((height + border) * (width + border))
+
+    printBorderAboveOrBelow(border, width, string, bitIsNotSetColor)
 
     for (y in 1 until height - 1 step 2) {
+      printBorderBeforeOrAfter(border, string, bitIsNotSetColor)
+
       for (x in 1 until width) {
         val currentRowBit = epcQrCode.getColorCodeAt(x, y)
         val nextRowBit = epcQrCode.getColorCodeAt(x, y + 1)
@@ -65,10 +77,14 @@ open class EpcQrCodeStringFormatter {
         }
       }
 
+      printBorderBeforeOrAfter(border, string, bitIsNotSetColor)
+
       string.appendLine()
     }
 
     if (height % 2 == 0) { // if last row is odd
+      printBorderBeforeOrAfter(border, string, bitIsNotSetColor)
+
       val y = height - 1
       for (x in 1 until width) {
         if (isBitSet(epcQrCode, x, y)) {
@@ -78,9 +94,13 @@ open class EpcQrCodeStringFormatter {
         }
       }
 
+      printBorderBeforeOrAfter(border, string, bitIsNotSetColor)
+
       string.appendLine()
     }
 
+    printBorderAboveOrBelow(border, width, string, bitIsNotSetColor)
+
     return string.toString()
   }
 
@@ -95,4 +115,21 @@ open class EpcQrCodeStringFormatter {
     return qrCodeBitColorCode < -1
   }
 
+
+  private fun printBorderAboveOrBelow(border: Int, width: Int, string: StringBuilder, bitIsNotSetColor: String) {
+    for (y in 0 until border) {
+      for (x in 1 until width + 2 * (border * 2)) {
+        string.append(bitIsNotSetColor)
+      }
+
+      string.appendLine()
+    }
+  }
+
+  private fun printBorderBeforeOrAfter(border: Int, string: StringBuilder, bitIsNotSetColor: String) {
+    for (x in 0 until (border * 2)) {
+      string.append(bitIsNotSetColor)
+    }
+  }
+
 }

EpcQrCodeNativeApp/src/nativeMain/kotlin/net.codinux.banking.epcqrcode/NativeApp.kt

@@ -6,7 +6,7 @@ class NativeApp {
   fun generateAndShowEpcQrCode(config: EpcQrCodeConfig) {
     val epcQrCode = EpcQrCodeGenerator().generateEpcQrCode(config, 40)
 
-    println(epcQrCode.qrCodeAsSmallString())
+    println(epcQrCode.qrCodeAsSmallString(4, true))
   }
 
 }