Creates a thumbnail image based on the current image. It is the responsibility of the calling routing to free the new thumbnail.
Width, in pixels, of the requested thumbnail image.
Height, in pixels, of the requested thumbnail image.
Callback function that you provide. During the process of creating or retrieving the thumbnail image, GDI+ calls this function to give you the opportunity to abort the process.
Optional. Pointer to a block of memory that contains data to be used by the callback function.