are raster (bitmap) images?
The Book, "Macromedia FLASH 5 Using Flash"
published by Macromedia, Inc. 2000
vector and bitmap graphics
display graphics in either vector or bitmap format.
graphics describe images using colored dots, called pixels,
arranged within a grid. For example, the image of a leaf is
described by the specific location and color value of each
pixel in he grid, creating an image much in the same manner
as in a mosaic.
you edit a bitmap graphic, you modify pixels, rather than
lines and curves. Bitmap graphics are resolution-dependent,
because the data describing the image is fixed to a grid of
a particular size. Editing a bitmap graphic can make the edges
of the image ragged as pixels are redistributed within the
grid. Displaying a bitmap graphic on an output device that
has a lower resolution than the image itself also degrades
the quality of its appearance.