File format identification and handling
Normally you don't use these classes directly, but via the Load
and Save functions described in Ravl.Core.IO
Suppose we wish to load some data from a file. The first question the
program must ask is `What format is this data in ?' There are two
ways to approach this. The first is to fix or specify explicitly the
format the file is in so the program knows what to expect. Second,
we can attempt to identify the file automaticaly.
Having to prepare large data sets for a program can be a headache as
for instance, there are dozens of ways of storing an image. Finding a
program to convert them between two particular formats can be time
consuming and difficult. While it is impossible to write input and
output routines for every conceivable format data may be presented in,
the user's life is made much easier if there are number of formats to
choose from.
Unfortunaly identifying files is not always simple, and in some cases
it is actually impossible. It is however possible to make very good
guesses, and provide the user is given the option of specifing the
format manually, it is a vast improvement over doing so for all
operations.
There are several clues that can be used to identify a file: the extension
on the filename often gives a good indication, or failing that the first
few bytes of the file sometimes contain a unique signature. Despite
this there is no single fool-proof method, so we have opted for the most
flexible approach, i.e. a method or function call which tells us if
a set of Input/Output (IO) routines can handle a particular file.
In order to keep the implementation of new file formats tractable,
each format the system recognises is represented by its own class. The
class is derived from an abstract representation of the file format,
called `FileFormatBaseC'. Each format then provides a method
for identifying, reading and writing a file of that format. All the
formats known to the system are kept in list, which is used for
handling any IO required for the program.
Normal classes:
Advanced classes:
Advanced functions:
Develop classes:
Develop functions: