Image Sources

ImageGear can load from and save images to any of 4 sources:

File on disk (accessed via the file-system Read and Write functions)
File on Internet (accessed via HTTP, FTP or Gopher GET)
File in C++ Stream (accessed via istream::read and ostream::write)
File in memory (accessed by memory address)

IGFormatsCtl Control defines a set of 4 objects to encapsulate these various image sources. These objects all implement the IIGIOLocation Interface and the IDispatchEx interface. Thus, your application (and ImageGear) can handle any of these via its IIGIOLocation Interface, until the actual image-source is needed. At that point, your application (or ImageGear) can use the IIGIOLocation Interface::Type property to determine the actual type of the object, and then switch to the appropriate (type-specific) interface.

When your application needs to load an image into an IGPage Object, the sequence of events is as follows:

Create (or identify a prior) IGPage Object to contain the image.
Create a location object (IGIOFile Object, IGIOMemory Object, etc.) to identify the location of the image file, and fill it in with the appropriate information.
Call the LoadPage Method of IGFormatsCtl Control to load the image into the IGPage Object.

Since loading images from files is the most common method of obtaining images, there is a special LoadDocumentFromFile Method of IGFormatsCtl Control that takes care of creating the IGIOFile Object for you.

In the case of multi-page files, LoadDocument Method and LoadDocumentFromFile Method of IGFormatsCtl Control will take care of creating an IGPage Object for each page in the file and loading them all.

When saving to URL, make sure to do the following:

The file format needs to be specified when saving to a URL.
An appropriate HTTP verb must be chosen, depending on the circumstances in which save to URL is being used.

See IGIOURL Object for more information.