Convert ALTO XML ID generation to conditional code based on the current pge

This will ensure, validated ALTO XML output is generated while keeping IDs for the first page consistent as before.

Author: jankal

src/api/altorenderer.cpp

@@ -51,6 +51,20 @@ static void AddBoxToAlto(const ResultIterator *it, PageIteratorLevel level,
   }
 }
 
+static std::string GetID(const char *prefix, int page_number, int counter) {
+  std::stringstream idstr;
+  // IDs will only have the counter for the first page to keep them consistent
+  // with the IDs assigned before this change was made.
+  // From the second page on, IDs will also contain the page number to make them unique.
+  if (page_number == 0) {
+    idstr << prefix << "_" << counter;
+  } else {
+    idstr << prefix << "_" << page_number << "_" << counter;
+  }
+
+  return idstr.str();
+}
+
 ///
 /// Append the ALTO XML for the beginning of the document
 ///
@@ -168,7 +182,7 @@ char *TessBaseAPI::GetAltoText(ETEXT_DESC *monitor, int page_number) {
       case PT_PULLOUT_IMAGE: {
         // Handle all kinds of images.
         // TODO: optionally add TYPE, for example TYPE="photo".
-        alto_str << "\t\t\t\t<Illustration ID=\"cblock_" << page_number << "_" << bcnt++ << "\"";
+        alto_str << "\t\t\t\t<Illustration ID=\"" << GetID("cblock", page_number, bcnt++) << "\"";
         AddBoxToAlto(res_it.get(), RIL_BLOCK, alto_str);
         alto_str << "</Illustration>\n";
         res_it->Next(RIL_BLOCK);
@@ -177,7 +191,7 @@ char *TessBaseAPI::GetAltoText(ETEXT_DESC *monitor, int page_number) {
       case PT_HORZ_LINE:
       case PT_VERT_LINE:
         // Handle horizontal and vertical lines.
-        alto_str << "\t\t\t\t<GraphicalElement ID=\"cblock_" << page_number << "_" << bcnt++ << "\"";
+        alto_str << "\t\t\t\t<GraphicalElement ID=\"" << GetID("cblock", page_number, bcnt++) << "\"";
         AddBoxToAlto(res_it.get(), RIL_BLOCK, alto_str);
         alto_str << "</GraphicalElement >\n";
         res_it->Next(RIL_BLOCK);
@@ -190,24 +204,24 @@ char *TessBaseAPI::GetAltoText(ETEXT_DESC *monitor, int page_number) {
     }
 
     if (res_it->IsAtBeginningOf(RIL_BLOCK)) {
-      alto_str << "\t\t\t\t<ComposedBlock ID=\"cblock_" << page_number << "_" << bcnt << "\"";
+      alto_str << "\t\t\t\t<ComposedBlock ID=\"" << GetID("cblock", page_number, bcnt) << "\"";
       AddBoxToAlto(res_it.get(), RIL_BLOCK, alto_str);
       alto_str << "\n";
     }
 
     if (res_it->IsAtBeginningOf(RIL_PARA)) {
-      alto_str << "\t\t\t\t\t<TextBlock ID=\"block_" << page_number << "_" << tcnt << "\"";
+      alto_str << "\t\t\t\t\t<TextBlock ID=\"" << GetID("block", page_number, tcnt) << "\"";
       AddBoxToAlto(res_it.get(), RIL_PARA, alto_str);
       alto_str << "\n";
     }
 
     if (res_it->IsAtBeginningOf(RIL_TEXTLINE)) {
-      alto_str << "\t\t\t\t\t\t<TextLine ID=\"line_" << page_number << "_" << lcnt << "\"";
+      alto_str << "\t\t\t\t\t\t<TextLine ID=\"" << GetID("line", page_number, lcnt) << "\"";
       AddBoxToAlto(res_it.get(), RIL_TEXTLINE, alto_str);
       alto_str << "\n";
     }
 
-    alto_str << "\t\t\t\t\t\t\t<String ID=\"string_" << page_number << "_" << wcnt << "\"";
+    alto_str << "\t\t\t\t\t\t\t<String ID=\"" << GetID("string", page_number, wcnt) << "\"";
     AddBoxToAlto(res_it.get(), RIL_WORD, alto_str);
     alto_str << " CONTENT=\"";