39.12. jpeg — Read and write JPEG files¶
Deprecated since version 2.6: The jpeg module has been removed in Python 3.
The module jpeg provides access to the jpeg compressor and decompressor
written by the Independent JPEG Group (IJG). JPEG is a standard for compressing
pictures; it is defined in ISO 10918.  For details on JPEG or the Independent
JPEG Group software refer to the JPEG standard or the documentation provided
with the software.
A portable interface to JPEG image files is available with the Python Imaging Library (PIL) by Fredrik Lundh. Information on PIL is available at http://www.pythonware.com/products/pil/.
The jpeg module defines an exception and some functions.
- 
exception jpeg.error¶
- Exception raised by - compress()and- decompress()in case of errors.
- 
jpeg.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 - gl.lrectread()return data can immediately be passed to- compress(). Currently only 1 byte and 4 byte pixels are allowed, the former being treated as greyscale and the latter as RGB color.- compress()returns a string that contains the compressed picture, in JFIF format.
- 
jpeg.decompress(data)¶
- Data is a string containing a picture in JFIF format. It returns a tuple - (data, width, height, bytesperpixel). Again, the data is suitable to pass to- gl.lrectwrite().
- 
jpeg.setoption(name, value)¶
- Set various options. Subsequent - compress()and- decompress()calls will use these options. The following options are available:- Option - Effect - 'forcegray'- Force output to be grayscale, even if input is RGB. - 'quality'- Set the quality of the compressed image to a value between - 0and- 100(default is- 75). This only affects compression.- 'optimize'- Perform Huffman table optimization. Takes longer, but results in smaller compressed image. This only affects compression. - 'smooth'- Perform inter-block smoothing on uncompressed image. Only useful for low- quality images. This only affects decompression. 
See also
- JPEG Still Image Data Compression Standard
- The canonical reference for the JPEG image format, by Pennebaker and Mitchell.
- Information Technology - Digital Compression and Coding of Continuous-tone Still Images - Requirements and Guidelines
- The ISO standard for JPEG is also published as ITU T.81. This is available online in PDF form.
