In ImageGear, an "image rectangle" defines the coordinates for the area of the bitmap that will be saved or displayed. The image rectangle represents a rectangular array of pixels from the bitmap that can include the whole image or any rectangular portion of the image.
You can leave the image rectangle set to its default, which includes the whole image, or you can specify a portion of the image by setting the image rectangle with IG_dspl_layout_set(). A call to this function is included in the example code in Saving an Image to Memory. You can also find a detailed description and example of this function's use in the Core Component API Function Reference.
For a more detailed description of the Image Rectangle and other ImageGear display rectangles, see Geometric Layout.