Creates the Subclass (Helper class) COM object and initializes data. Calls the Subclass's Open for further initialization

None  

object.Open [Source], [mode]

The Open Method syntax has these parts:

The settings for mode are:

Constant		Value	Description
	mcSTREAM_READ	1	open the file to read it into the image
	mcSTREAM_WRITE	2	open the file to write it to a new or existing image file
	mcSTREAM_READ_WRITE	3	open the file for both access (may not work for all formats)

The Source parameter can be a filename or an IStream/IStorage object. If the Source parameter is VT_NULL or VT_EMPTY or VT_MISSING (ie not there) then the local property, FileName, is checked. If this is NULL, then an error is returned.

This method will set the FileFormatName, FileName, and Source properties, It creates the Subclass and calls Open on it for further initialization. At return time, the Image data is not actually open, but everything is in place for a call to Read or Write.

The second parameter, Mode, is one of mcfmFileMode members, indicating read, write, or both file permissions. Caution in using the mcSTREAM_READ_WRITE (both) parameter, since some subclasses may not support reading a file with write capabilities.

If a file is opened for Writing, but the type of Image file it contains cannot be determined by the file name, a “Magic” number scheme will be tried to determine the Image type. If this also fails, an error is returned.