[pdftex] Re: Best bitmap image format?

Hartmut Henkel hartmut_henkel at gmx.de
Mon Feb 27 19:26:25 CET 2006

On Mon, 27 Feb 2006, Rolf.Niepraschk at ptb.de wrote:

> Hartmut schrieb am 27.02.2006 08:37:45:
> > Type  Compression Embedding
> >
> > JPEG  DCT...      native: copy image relevant stream subset
> > PNG   zlib        native: uncompress + re-compress, or copy
> > TIFF  LZW         via PDF file
> > FAX   CCITT       via PDF file
> > JBIG2 JBIG2       via PDF file
> > JPX   JPEG2000    via PDF file
> What's about gif pictures (specially animated gif pictures)?

The PDF standard defines a certain set of generic "Filters", and PDF
readers use them to uncompress and display the image data streams.
Filters are e. g. DCTDecode (for JPEG), LZWDecode, FlateDecode (for
PNG), CCITTFaxDecode, JBIG2Decode, RunLengthDecode. The number of
components, image size in pixels, bits per pixel, and other decoder
parameters are also given separately.

The GIF format seems to use LZW, so one could maybe write a native
driver/re-encoder for GIF for later decoding by the LZWDecode filter.
But this would be only single images, it seems PDF doesn't have a means
for handling animated GIF/LZW image sequences.

Regards, Hartmut

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