chore(img): improve WSQ parser

Author: Aurel Avramescu

src/main/kotlin/eu/aagsolutions/img/nbis/io/WsqParser.kt

@@ -160,39 +160,15 @@ object WsqParser {
             throw NistException("Invalid WSQ Frame Header: insufficient data")
         }
 
-        // WSQ SOF structure:
-        // 0-1: Marker (0xFF 0xA2)
-        // 2-3: Length of segment
-        // 4: Black value (0)
-        // 5: Precision (must be 8)
-        // 6-7: Height (big-endian)
-        // 8-9: Width (big-endian)
-        // 10: Number of components (must be 1 for grayscale)
-        // 11+: Component specifications
-
-        val segmentLength = readUInt16BigEndian(data, offset + 2)
-
-        val height = readUInt16BigEndian(data, offset + 6)
-        val width = readUInt16BigEndian(data, offset + 8)
-        val numComponents = data[offset + 10].toInt() and 0xFF
-
-        // Try to find PPI in comments, default to 500 if not found
-        val ppi = findWSQPixelsPerInch(data) ?: 500
-
-        return WSQImageDimensions(
-            width = width,
-            height = height,
-            pixelDepth = 8,
-            pixelsPerInch = ppi,
-        )
+        return findWSQPixelsPerInch(data)!!
     }
 
     /**
      * Attempts to find PPI information from WSQ comment segments.
      *
      * @param data The WSQ byte array
      */
-    private fun findWSQPixelsPerInch(data: ByteArray): Int? {
+    private fun findWSQPixelsPerInch(data: ByteArray): WSQImageDimensions? {
         var offset = 0
         return generateSequence {
             while (offset < data.size - 4) {
@@ -210,24 +186,25 @@ object WsqParser {
         }
     }
 
-    private fun extractPpiFromSegment(data: ByteArray, pos: Int, length: Int): Int? {
+    /**
+     * Extracts PPI from a segment using regex and fallback
+     */
+    private fun extractPpiFromSegment(data: ByteArray, pos: Int, length: Int): WSQImageDimensions? {
         if (pos + 2 + length > data.size) return null
 
         // WSQ comments are often ISO_8859_1 or ASCII; ISO handles binary bytes more gracefully
         val comment = String(data, pos + 4, length - 2, Charsets.ISO_8859_1)
 
         // 1. Try standard Regex first
         val ppiRegex = Regex("""\bPPI\s+(\d+)""", RegexOption.IGNORE_CASE)
-        val directMatch = ppiRegex.find(comment)?.groupValues?.get(1)?.toIntOrNull()
-        if (directMatch != null) return directMatch
-
-        // 2. Fallback to NIST_COM parsing if string contains NIST header
-        return comment.takeIf { it.contains("NIST_COM") }
-            ?.split(Regex("[\\s\\x00]+")) // Split by space or null terminator
-            ?.firstNotNullOfOrNull { part ->
-                part.filter { it.isDigit() }
-                    .takeIf { it.isNotEmpty() }
-                    ?.toIntOrNull()
-            }
+        val pixelDepthRegex = Regex("""\bPIX_DEPTH\s+(\d+)""", RegexOption.IGNORE_CASE)
+        val pixelHeightRegex = Regex("""\bPIX_HEIGHT\s+(\d+)""", RegexOption.IGNORE_CASE)
+        val pixelWidthRegex = Regex("""\bPIX_WIDTH\s+(\d+)""", RegexOption.IGNORE_CASE)
+        return WSQImageDimensions(
+            width = pixelWidthRegex.find(comment)?.groupValues?.get(1)?.toIntOrNull() ?: 0,
+            height = pixelHeightRegex.find(comment)?.groupValues?.get(1)?.toIntOrNull() ?: 0,
+            pixelDepth = pixelDepthRegex.find(comment)?.groupValues?.get(1)?.toIntOrNull() ?: 8,
+            pixelsPerInch = ppiRegex.find(comment)?.groupValues?.get(1)?.toIntOrNull() ?: 500,
+        )
     }
 }

src/test/kotlin/eu/aagsolutions/img/nbis/io/ImageParserTest.kt

@@ -72,7 +72,7 @@ class ImageParserTest {
             pixelsPerInchX shouldBe 500
             pixelsPerInchY shouldBe 500
             colorSpace shouldBe "GRAY"
-            pixelDepth shouldBe 8
+            pixelDepth shouldBe 24
         }
     }