PICT file format support in IDL (READ_PICT & WRITE_PICT)

There is no problem reading images stored in the PICT file format if the file was created in IDL. Nor is there a problem for other applications to read the PICT files that are created in IDL. However, sometimes it might be difficult to read PICT files into IDL which were created by other applications.

The reason for the difficulty is that
WRITE_PICT and READ_PICT are hard coded into IDL and support the reading and writing of an older and obsolete version of the PICT file format. Newer versions of PICT file format readers can read these older versions due to successful implementations for backward compatibility.

If the PICT file originates from somewhere other than IDL and
QUERY_PICT returns a 0, it is likely that there are tags in that file that IDL does not know how to handle. Therefore, it can not be read. If this is the case, it is recommend that the PICT file be converted to another image file format (such as PNG, JPEG, TIFF, etc.), and then read it into IDL.

If the PICT file originates from somewhere other than IDL but is very old and one which should probably be able to read, yet
QUERY_PICT still returns a 0, check to see if the file has both raster and vector data. IDL can only handle raster data in a PICT file.