The preview package for LaTeX allows for the processing of selected
parts of a LaTeX input file. This package extracts indicated pieces
from a source file (typically displayed equations, figures and
graphics) and typesets with their base point at the (1in,1in) magic
location, shipping out the individual pieces on separate pages without
any page markup. You can produce either DVI or PDF files, and options
exist that will set the page size separately for each page. In that
manner, further processing (as with Ghostscript or dvipng) will be
able to work in a single pass.
The main purpose of this package is the extraction of certain
environments (most notably displayed formulas) from LaTeX sources as
graphics. This works with DVI files postprocessed by either Dvips and
Ghostscript or dvipng, but it also works when you are using PDFTeX for
generating PDF files (usually also postprocessed by Ghostscript).
The tex-preview package is generated from the AUCTeX package for
Emacs.