Graphics – any objects you see in a page which are not text – are stored in a number of different ways.
'Bitmapped graphics' are mosaics of monochrome (black-and-white) or colored pixels. Some formats consist entirely of such images e.g. BMP, JPEG, PCL3GUI while others, e.g. PDF files, can contain both text and graphics.
Images in AFP, PDF, TIFF and PNG files may contain transparent pixels, the transparency information being stored in an extra layer in the image (the "alpha" channel) much like a "soft mask". Each pixel in a soft mask assigns a degree of transparency to the base image. This is how the edges of an image can be made to fade into the background, or to allow an underlying image to show through it (e.g. in Windows title-bars).
Alpha channel transparency is readily propagated into PDF documents, so the exported PDF files are relatively compact. Images with transparency exported in other formats, however, may require the whole page to be imaged, which usually results in relatively large files.
Some formats also support 'shading': areas of black and white pixels arranged in a repeating pattern. These areas are often used as backgrounds for other elements, but they are liable to cause problems when layered on top of one another and exported in different format. (For example, the 'white' pixels in PCL shading patterns are transparent but the 'white' pixels in PDF patterns may be opaque.) These options may be configured to handle such situations: Transparent white, Keep original element order and Ignore Shading.
If using a color printer, you may opt to convert monochrome shades to gray-scale, see Shading options.
The RedTitan Color Management System handles CMYK to RGB color conversion for EscapeE. The 'Force monochrome' option can be used to change colored images to 'gray-scale' or 'black-and-white' and supports a variety of conversion options. Several smoothing methods are provided to ensure good results when scaling color and monochrome images down for printing or viewing on-screen. See Image import/export options.
You may opt to remove images and/or shading from documents, for example when you just need to read the text, or to keep file-sizes down. See Setting the 'Ignore' options.