fpexif: Fix incorrect copying of XMP meta data when a file with XMP is re-saved.

git-svn-id: https://svn.code.sf.net/p/lazarus-ccr/svn@7983 8e941d3f-bd1b-0410-a28a-d453659cc2b4

components/fpexif/fpeexifreadwrite.pas

@@ -803,7 +803,7 @@ begin
   FExifSegmentStartPos := AStream.Position;
   AStream.WriteBuffer(SEGMENT_MARKER[0], 2);
   // Next two zero bytes are the size of the entire Exif segiment, they will be
-  // replaced when the segment is completely written. For this, we store the
+  // replaced when the segment is completely written. For this, we stored the
   // offset to the beginning of the EXIF segment in FExifSegmentStartPos.
   AStream.WriteBuffer(SIZE, 2);
   AStream.WriteBuffer(EXIF_SIGNATURE[0], 6);

components/fpexif/fpemetadata.pas

@@ -230,7 +230,7 @@ begin
   AStream.Position := startPos;
 
   // ... and write the segment size.
-  w := BEToN(segmentSize);
+  w := NToBE(segmentSize);
   AStream.WriteBuffer(w, SizeOf(w));
 
   // Rewind stream to the end
@@ -393,18 +393,16 @@ type
   TSegmentHeader = packed record
     Key: byte;
     Marker: byte;
-    Size: Word;
+    Size: Word;  // total size of the segment without "Key" and "Marker", but with "Size"
   end;
 const
-  SOI_MARKER: array[0..1] of byte = ($FF, $D8);
   XMP_SIGNATURE = 'http://ns.adobe.com/xap/1.0/';
 var
   header: TSegmentHeader;
-  headerSize, newHeaderSize: Word;
+  headerSize: Word;
   n, count: Int64;
   savedPos: Int64;
-  jfif: TJpegJFIFSegment;
+  s: RawByteString;
-  s: String;
 begin
   // Write the header segment and all metadata segments stored in TImgInfo
   // to the beginning of the stream
@@ -424,10 +422,8 @@ begin
 
     // Some images do not specify the segment length correctly and fill the
     // space to the next segment with zero bytes.
-    if LongInt(header) = 0 then begin
+    if (header.Key = 0) then begin
-      n := 0;
+      repeat until AInputStream.ReadByte = $FF;
-      while AInputStream.ReadByte = 0 do
-        inc(n);
       AInputStream.Position := AInputStream.Position - 1;
       n := AInputStream.Read(header, SizeOf(Header));
       if n <> SizeOf(Header) then
@@ -438,39 +434,32 @@ begin
       Error(rsJpegSegmentMarkerExpected);
     headerSize := BEToN(header.Size);
 
-    // Save stream position before segment size value.
+    // Stream position at start of segment header
+    savedPos := AInputStream.Position - SizeOf(header);
+    // Save stream position after marker bytes, i.e. at begin of segment size value.
     savedPos := AInputStream.Position - 2;
+
     case header.Marker of
       M_SOI:
         headerSize := 0;
       M_JFIF, M_IPTC, M_COM:  // These segments were already written by WriteJpeg
         ;
       M_EXIF:
-        // there may be also the XMP segment which has the same key $E1.
         begin
+          // XMP segment found which has the same key $E1 as the normal EXIF segment.
           SetLength(s, Length(XMP_SIGNATURE));
           AInputStream.Read(s[1], Length(XMP_SIGNATURE));
           if s = XMP_SIGNATURE then
           begin
-            // XMP segment found --> write it back as it is (needs to be fixed to write current meta data)
+            // Return to where the segment begins
-            newHeaderSize := (Trunc(headerSize / 256) + 1) * 256 - SizeOf(header);
+            AInputStream.Position := savedPos - 2;
-            SetLength(s, newHeaderSize - Length(XMP_SIGNATURE));
+            // Copy entire segment incl header
-            FillChar(s[1], Length(s), 0);
+            n := AOutputStream.CopyFrom(AInputStream, headerSize + 2);
-            AInputStream.Read(s[1], headerSize);
+            if n <> Int64(headerSize) + 2 then
-            header.Size := NToBE(newHeaderSize);
-            AOutputStream.Write(header, SizeOf(Header));
-            AOutputStream.Write(XMP_SIGNATURE, Length(XMP_SIGNATURE));
-            AOutputStream.Write(s[1], Length(s));
-            {
-            AInputStream.Position := savedPos - 4;
-            n := AOutputStream.CopyFrom(AInputStream, Int64(header.Size) + 2);
-            if n <> Int64(header.Size) + 2 then
               Error(rsJpegReadWriteErrorInSegment);
-              }
+          end else
-          end
-          else
           begin
-            // EXIF segment found. But this already has been written by WriteJpeg -> nothing to do
+            // Normal EXIF segment found. But this already has been written by WriteJpeg -> nothing to do
           end;
         end;
       M_SOS:
@@ -479,14 +468,16 @@ begin
           // --> just copy the rest of the file
           count := AInputStream.Size - savedPos;
           AInputStream.Position := savedPos;
-          AOutputStream.WriteBuffer(header, 2);
+          AOutputStream.Write(header, 2);
           n := AOutputStream.CopyFrom(AInputStream, count);
           if n <> count then
             Error(rsJpegCompressedDataWriting);
           break;
         end;
       else
-        AInputStream.Position := AInputStream.Position - 4;  // go back to where the segment begins
+        // Return to where the segment begins
+        AInputStream.Position := AInputStream.Position - 4;
+        // Copy entire segment incl header
         n := AOutputStream.CopyFrom(AInputStream, headerSize + 2);
         if n <> Int64(headerSize) + 2 then
           Error(rsJpegReadWriteErrorInSegment);