Class representing own FreeImage-Plugins.
Namespace:
FreeImageAPI.PluginsAssembly: FreeImageNET (in FreeImageNET.dll)
Syntax
| C# |
|---|
public abstract class LocalPlugin |
| Visual Basic (Declaration) |
|---|
Public MustInherit Class LocalPlugin |
| Visual C++ |
|---|
public ref class LocalPlugin abstract |
Remarks
FreeImages itself is plugin based. Each supported format is integrated by a seperat plugin,
that handles loading, saving, descriptions, identifing ect.
And of course the user can create own plugins and use them in FreeImage.
To do that the above mentioned predefined methodes need to be implemented.
The class below handles the creation of such a plugin. The class itself is abstract
as well as some core functions that need to be implemented.
The class can be used to enable or disable the plugin in FreeImage after regististration or
retrieve the formatid, assigned by FreeImage.
The class handles the callback functions, garbage collector and pointer operation to make
the implementation as user friendly as possible.
How to:
There are two functions that need to be implemented:
GetImplementedMethods()()() and
FormatProc()()().
GetImplementedMethods()()() is used by the constructor
of the abstract class. FreeImage wants a list of the implemented functions. Each function is
represented by a function pointer (a .NET Delegate). In case a function
is not implemented FreeImage receives an empty delegate). To tell the constructor
which functions have been implemented the information is represented by a disjunction of
LocalPlugin..::.MethodFlags.
For example:
return MethodFlags.LoadProc | MethodFlags.SaveProc;
The above statement means that LoadProc and SaveProc have been implemented by the user.
Keep in mind, that each function has a standard implementation that has static return
values that may cause errors if listed in
GetImplementedMethods()()() without a real implementation.
FormatProc()()() is used by some checks of FreeImage and
must be implemented. LoadProc(FreeImageIO%, fi_handle, Int32, Int32, IntPtr) for example can be
implemented if the plugin supports reading, but it doesn't have to, the plugin could only
be used to save an already loaded bitmap in a special format.
