Re-factoring of metadata handling in output compressor classes and addition of more complete metadata embedding for PNG.

Author: ruven

ChangeLog

@@ -1,6 +1,8 @@
 29/06/2024:
 	- Updated autoconf tiff m4 to search for tiffio.h rather than just tiff.h when using TIFFOpen().
 	- Switched metadata assignment within input image classes to use more efficient map insert() syntax.
+	- Re-factoring of metadata handling in output compressor classes and addition of more complete metadata
+	  embedding for PNG.
 
 
 29/05/2024:

src/CVT.cc

@@ -502,6 +502,10 @@ void CVT::send( Session* session ){
   }
 
 
+  // Add metadata
+  compressor->setMetadata( (*session->image)->metadata );
+
+
   // Set the physical output resolution for this particular view and zoom level
   if( (*session->image)->dpi_x > 0 && (*session->image)->dpi_y > 0 ){
     float dpi_x = (*session->image)->dpi_x * (float) im_width / (float) (*session->image)->getImageWidth();
@@ -513,14 +517,14 @@ void CVT::send( Session* session ){
     }
   }
 
-  // Set ICC profile if of a reasonable size
+  // Embed ICC profile if of a reasonable size
   if( session->view->embedICC() && ((*session->image)->getMetadata("icc").size()>0) ){
     if( (*session->image)->getMetadata("icc").size() < 65536 ){
       if( session->loglevel >= 3 ){
 	*(session->logfile) << "CVT :: Embedding ICC profile with size "
 			    << (*session->image)->getMetadata("icc").size() << " bytes" << endl;
       }
-      compressor->setICCProfile( (*session->image)->getMetadata("icc") );
+      compressor->embedICCProfile( true );
     }
     else{
       if( session->loglevel >= 3 ){
@@ -530,13 +534,13 @@ void CVT::send( Session* session ){
     }
   }
 
-  // Add XMP metadata if this exists
+  // Always embed XMP metadata in CVT function
   if( (*session->image)->getMetadata("xmp").size() > 0 ){
     if( session->loglevel >= 3 ){
       *(session->logfile) << "CVT :: Embedding XMP metadata with size "
 			  << (*session->image)->getMetadata("xmp").size() << " bytes" << endl;
     }
-    compressor->setXMPMetadata( (*session->image)->getMetadata("xmp") );
+    compressor->embedXMPMetadata( true );
   }
 
 

src/Compressor.h

@@ -1,6 +1,6 @@
 /*  Generic compressor class - extended by JPEG and PNG Compressor classes
 
-    Copyright (C) 2017-2023 Ruven Pillay
+    Copyright (C) 2017-2024 Ruven Pillay
 
     This program is free software; you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -23,9 +23,8 @@
 
 
 
-#include <string>
 #include "RawTile.h"
-
+#include <map>
 
 
 /// Base class for IIP output images
@@ -52,12 +51,23 @@ class Compressor {
   /** Units can be 0 for unknown, 1 for dots/inch or 2 for dots/cm */
   int dpi_units;
 
+  /// Metadata
+  std::map <const std::string, const std::string> metadata;
+
   /// ICC Profile
+  bool embedICC;
   std::string icc;
 
   /// XMP metadata
+  bool embedXMP;
   std::string xmp;
 
+  /// Write metadata
+  virtual void writeMetadata() {};
+
+  /// Write DPI
+  virtual void writeResolution() {};
+
   /// Write ICC profile
   virtual void writeICCProfile() {};
 
@@ -76,12 +86,24 @@ class Compressor {
     header_size( 0 ),
     dpi_x( 0 ),
     dpi_y( 0 ),
-    dpi_units( 0 ) {};
+    dpi_units( 0 ),
+    embedICC( false ),
+    embedXMP( false ) {};
 
 
   virtual ~Compressor() {};
 
 
+  /// Return the image header size
+  /** @return header size in bytes */
+  unsigned int getHeaderSize() const { return header_size; };
+
+
+  /// Return a pointer to the image header itself
+  /** @return binary header blob */
+  unsigned char* getHeader() { return header; };
+
+
   /// Get the current quality level
   inline int getQuality() const { return Q; }
 
@@ -94,24 +116,38 @@ class Compressor {
   inline void setResolution( float x, float y, int units ){ dpi_x = x; dpi_y = y; dpi_units = units; };
 
 
-  /// Set the ICC profile
-  /** @param profile ICC profile string */
-  inline void setICCProfile( const std::string& profile ){ icc = profile; }
+  /// Embed ICC profile
+  /** @param embed Whether ICC profile should be embedded */
+  inline void embedICCProfile( const bool embed ){ this->embedICC = embed; }
 
 
-  /// Set XMP metadata
-  /** @param x XMP metadata string */
-  inline void setXMPMetadata( const std::string& x ){ xmp = x; }
+  /// Embed XMP metadata
+  /** @param embed Whether XMP metadata should be embedded */
+  inline void embedXMPMetadata( const bool embed ){ this->embedXMP = embed; }
 
 
-  /// Return the image header size
-  /** @return header size in bytes */
-  virtual unsigned int getHeaderSize() const { return 0; };
+  /// Set general metadata
+  /** @param metadata Metadata list */
+  inline void setMetadata( const std::map <const std::string, const std::string>& metadata )
+  {
+    this->metadata = std::map <const std::string, const std::string>( metadata );
 
+    // Extract ICC profile if it exists and remove from list
+    std::map<const std::string, const std::string> :: const_iterator it;
+    it = this->metadata.find("icc");
+    if( it != this->metadata.end() ){
+      icc = it->second;
+      this->metadata.erase( it );
+    }
+
+    // Extract XMP chunk if it exists and remove from list
+    it = this->metadata.find("xmp");
+    if( it != this->metadata.end() ){
+      xmp = it->second;
+      this->metadata.erase( it );
+    }
+  };
 
-  /// Return a pointer to the image header itself
-  /** @return binary header blob */
-  virtual unsigned char* getHeader() { return NULL; };
 
 
   /// Initialise strip based compression
@@ -147,11 +183,6 @@ class Compressor {
   virtual unsigned int Compress( RawTile& t ) { return 0; };
 
 
-  /// Add metadata to the image header
-  /** @param m metadata */
-  virtual void addXMPMetadata( const std::string& m ) {};
-
-
   /// Get mime type
   /** @return IANA mime type as const char* */
   virtual const char* getMimeType() const { return "image/example"; };

src/IIPImage.h

@@ -174,7 +174,7 @@ class IIPImage {
   std::vector<unsigned int> histogram;
 
   /// STL map to hold string metadata
-  std::map <const std::string, std::string> metadata;
+  std::map <const std::string, const std::string> metadata;
 
   /// Image modification timestamp
   time_t timestamp;

src/JPEGCompressor.cc

@@ -1,6 +1,6 @@
 /*  JPEG class wrapper to ijg jpeg library
 
-    Copyright (C) 2000-2023 Ruven Pillay.
+    Copyright (C) 2000-2024 Ruven Pillay
 
     This program is free software; you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -228,10 +228,8 @@ void JPEGCompressor::InitCompression( const RawTile& rawtile, unsigned int strip
   cinfo.in_color_space = ( channels == 3 ? JCS_RGB : JCS_GRAYSCALE );
   jpeg_set_defaults( &cinfo );
 
-  // Set our physical output resolution (JPEG only supports integers)
-  cinfo.X_density = round( dpi_x );
-  cinfo.Y_density = round( dpi_y );
-  cinfo.density_unit = dpi_units;
+  // Add DPI
+  writeResolution();
 
   // Set compression point quality (highest, but possibly slower depending
   //  on hardware) - must do this after we've set the defaults!
@@ -402,10 +400,8 @@ unsigned int JPEGCompressor::Compress( RawTile& rawtile )
   cinfo.in_color_space = ( channels == 3 ? JCS_RGB : JCS_GRAYSCALE );
   jpeg_set_defaults( &cinfo );
 
-  // Set our physical output resolution (JPEG only supports integers)
-  if( dpi_x ) cinfo.X_density = round( dpi_x );
-  if( dpi_y ) cinfo.Y_density = round( dpi_y );
-  if( dpi_x || dpi_y ) cinfo.density_unit = dpi_units;
+  // Add DPI
+  writeResolution();
 
   // Set compression quality (fastest, but possibly slower depending
   //  on hardware) - must do this after we've set the defaults!
@@ -468,6 +464,17 @@ unsigned int JPEGCompressor::Compress( RawTile& rawtile )
 
 
 
+// Write DPI information
+void JPEGCompressor::writeResolution()
+{
+  // Set our physical output resolution (JPEG only supports integers)
+  if( dpi_x ) cinfo.X_density = round( dpi_x );
+  if( dpi_y ) cinfo.Y_density = round( dpi_y );
+  if( dpi_x || dpi_y ) cinfo.density_unit = dpi_units;
+}
+
+
+
 // Write ICC profile into JPEG header if profile has been set
 // Function *must* be called AFTER calling jpeg_start_compress() and BEFORE
 // the first call to jpeg_write_scanlines().
@@ -478,14 +485,13 @@ unsigned int JPEGCompressor::Compress( RawTile& rawtile )
 // See the copyright notice in COPYING.ijg for details
 void JPEGCompressor::writeICCProfile()
 {
+  // Skip if profile embedding disabled
+  if( !embedICC || icc.empty() ) return;
+
   unsigned int num_markers;     // total number of markers we'll write
   int cur_marker = 1;           // per spec, counting starts at 1
   unsigned int length;          // number of bytes to write in this marker
 
-  // Skip if our profile has zero size or is too big
-  //  if( icc.size() == 0 || icc.size() > MAX_DATA_BYTES_IN_MARKER ) return;
-  if( icc.empty() ) return;
-
   unsigned int icc_data_len = icc.size();
   const char* icc_data_ptr = icc.c_str();
 
@@ -542,7 +548,7 @@ void JPEGCompressor::writeICCProfile()
 void JPEGCompressor::writeXMPMetadata()
 {
   // Make sure our XMP data has a valid size (namespace prefix is 29 bytes)
-  if( xmp.empty() || xmp.size()>(65536-XMP_PREFIX_SIZE) ) return;
+  if( !embedXMP || xmp.empty() || xmp.size()>(65536-XMP_PREFIX_SIZE) ) return;
 
   // The XMP data in a JPEG stream needs to be prefixed with a zero-terminated ID string
   // ref http://www.adobe.com/content/dam/Adobe/en/devnet/xmp/pdfs/cs6/XMPSpecificationPart3.pdf (pp13-14)

src/JPEGCompressor.h

@@ -1,6 +1,6 @@
 /*  JPEG class wrapper to ijg libjpeg library
 
-    Copyright (C) 2000-2023 Ruven Pillay.
+    Copyright (C) 2000-2024 Ruven Pillay.
 
     This program is free software; you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -73,6 +73,9 @@ class JPEGCompressor: public Compressor{
   iip_destination_mgr dest_mgr;
   iip_dest_ptr dest;
 
+  /// Write DPI
+  void writeResolution();
+
   /// Write ICC profile
   void writeICCProfile();
 
@@ -128,12 +131,6 @@ class JPEGCompressor: public Compressor{
   /** @param t tile of image data */
   unsigned int Compress( RawTile& t );
 
-  /// Return the JPEG header size
-  inline unsigned int getHeaderSize() const { return header_size; }
-
-  /// Return a pointer to the header itself
-  inline unsigned char* getHeader() { return header; }
-
   /// Return the JPEG mime type
   inline const char* getMimeType() const { return "image/jpeg"; }
 

src/JTL.cc

@@ -141,16 +141,21 @@ void JTL::send( Session* session, int resolution, int tile ){
   }
 
 
+  // Add metadata
+  compressor->setMetadata( (*session->image)->metadata );
+
+
   // Embed ICC profile
-  if( session->view->embedICC() && ((*session->image)->getMetadata("icc").size()>0) ){
+  if( session->view->embedICC() && (*session->image)->metadata["icc"].size() > 0 ){
     if( session->loglevel >= 3 ){
       *(session->logfile) << "JTL :: Embedding ICC profile with size "
 			  << (*session->image)->getMetadata("icc").size() << " bytes" << endl;
     }
-    compressor->setICCProfile( (*session->image)->getMetadata("icc") );
+    compressor->embedICCProfile( true );
   }
 
 
+
   RawTile rawtile = tilemanager.getTile( resolution, tile, session->view->xangle,
 					 session->view->yangle, session->view->getLayers(), ct );
 

src/OBJ.cc

@@ -112,9 +112,8 @@ void OBJ::run( Session* s, const std::string& a )
     stringstream json;
     json << "{ ";
 
-    map <const string, string> metadata = (*session->image)->metadata;
-    map<const string,string> :: const_iterator i;
-    for( i = metadata.begin(); i != metadata.end(); i++ ){
+    map <const string, const string> :: const_iterator i;
+    for( i = (*session->image)->metadata.begin(); i != (*session->image)->metadata.end(); i++ ){
       if( i->first == "icc" || i->first == "xmp" ) continue;
       if( (i->second).length() ) json << endl << "\t\"" << i->first << "\": \"" << i->second << "\",";
     }