mirror of
https://github.com/python/cpython.git
synced 2024-12-12 03:04:15 +08:00
52 lines
1.9 KiB
TeX
52 lines
1.9 KiB
TeX
\section{Built-in Module \sectcode{jpeg}}
|
|
\bimodindex{jpeg}
|
|
|
|
The module jpeg provides access to the jpeg compressor and
|
|
decompressor written by the Independent JPEG Group. JPEG is a (draft?)
|
|
standard for compressing pictures. For details on jpeg or the
|
|
Indepent JPEG Group software refer to the JPEG standard or the
|
|
documentation provided with the software.
|
|
|
|
The jpeg module defines these functions:
|
|
|
|
\renewcommand{\indexsubitem}{(in module jpeg)}
|
|
\begin{funcdesc}{compress}{data\, w\, h\, b}
|
|
Treat data as a pixmap of width w and height h, with b bytes per
|
|
pixel. The data is in sgi gl order, so the first pixel is in the
|
|
lower-left corner. This means that lrectread return data can
|
|
immedeately be passed to compress. Currently only 1 byte and 4 byte
|
|
pixels are allowed, the former being treaded as greyscale and the
|
|
latter as RGB color. Compress returns a string that contains the
|
|
compressed picture, in JFIF format.
|
|
\end{funcdesc}
|
|
|
|
\begin{funcdesc}{decompress}{data}
|
|
Data is a string containing a picture in JFIF format. It returns a
|
|
tuple
|
|
\code{(\var{data}, \var{width}, \var{height}, \var{bytesperpixel})}.
|
|
Again, the data is suitable to pass to lrectwrite.
|
|
\end{funcdesc}
|
|
|
|
\begin{funcdesc}{setoption}{name\, value}
|
|
Set various options. Subsequent compress and decompress calls
|
|
will use these options. The following options are available:
|
|
\begin{description}
|
|
\item[\code{'forcegray'}]
|
|
Force output to be grayscale, even if input is RGB.
|
|
|
|
\item[\code{'quality'}]
|
|
Set the quality of the compressed image to a
|
|
value between \code{0} and \code{100} (default is \code{75}). Compress only.
|
|
|
|
\item[\code{'optimize'}]
|
|
Perform huffman table optimization. Takes longer, but results in
|
|
smaller compressed image. Compress only.
|
|
|
|
\item[\code{'smooth'}]
|
|
Perform inter-block smoothing on uncompressed image. Only useful for
|
|
low-quality images. Decompress only.
|
|
\end{description}
|
|
\end{funcdesc}
|
|
|
|
Compress and uncompress raise the error jpeg.error in case of errors.
|