Comment example for Delphi

This example does the following:

1.	Loads an image from a TIFF file.
2.	Updates the current comment array by reading comments from the file.
3.	Modifies one of the comments.
4.	Modifies and saves the file.
5.	Reads the comment that was saved, and displays it in a message box.

This example handles only string comments. For more complex comments, refer to Exif Examples.

var
   MyCommentText: String; //String for CMNT_SZDESC
     FilePath: String; //File to be updated
     i: Longint; //Loop counter and array index
     RasterIO: LEADRasterIO;
   RasterProc: LEADRasterProcess;
   RasterVarEmpty: LEADRasterVariant;
   RasterVar: LEADRasterVariant;

begin
   RasterIO:= CreateComObject (CLASS_LEADRasterIO) as LEADRasterIO;
   RasterProc:= CreateComObject (CLASS_LEADRasterProcess ) as LEADRasterProcess;
   RasterVarEmpty:= coLEADRasterVariant.Create ( );
   RasterVar:= coLEADRasterVariant.Create ( );

   //Specify the file that we will update.
   FilePath := 'c:\temp\Test.tif';
   //Get all of the current comments from the file.
   //Temporarily disable method errors so that we do not fail when comments are missing.
   RasterIO.EnableMethodErrors := False;
   for i := 0 to CMNT_LAST do
   begin
      RasterIO.Comment[i]:= RasterVarEmpty;
      RasterIO.Comment[i]:= RasterIO.ReadComment(LEADRasterView1.Raster, FilePath, 1, i);
   end;
     //Load and modify the image.
     RasterIO.EnableMethodErrors := False;
     RasterIO.Load (LEADRasterView1.Raster, FilePath, 0, 0, 1);
     RasterProc.Reverse (LEADRasterView1.Raster);
     //Update the CMNT_SZDESC comment.
     MyCommentText := Chr(13) + 'This image has been reversed.';
   RasterVar.Type_:= VALUE_STRING;
   RasterVar:= RasterIO.Comment[CMNT_SZDESC];
   RasterVar.StringValue:= RasterVar.StringValue + MyCommentText;

     RasterIO.Comment[CMNT_SZDESC]:= RasterVar;
     //Save the file and read the comment that we saved.
     RasterIO.Save (LEADRasterView1.Raster, FilePath, FILE_TIF, LEADRasterView1.Raster.BitmapBits, 0, SAVE_OVERWRITE);
     RasterVar:= RasterIO.ReadComment (LEADRasterView1.Raster, FilePath, 1, CMNT_SZDESC);
     //Display the message
     ShowMessage (RasterVar.StringValue);
     //Clear the comments from memory
     for i := 0 to CMNT_LAST do
      RasterIO.Comment [i]:= RasterVarEmpty;
end;