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Cisco
compatible TIFF files can be created by the Black Ice pritner
drivers version 9.75 and higher. Cisco routers require a
TIFF file in a special format. The Cisco TIFF file begins
with an 8-byte TIFF image file header identifier which contains
the offset for the first Image File Directory
(IFD), followed by the first Image File Directory (IFD),
and the Image data. Followed by the next IFD, the next Image
data is a chain of images in the TIFF file.
A
conventional TIFF file begins with an 8-byte image file header
which contains the offset for the first Image File Directory
(IFD),
followed by the Image data, which is followed by the first Image
File Directory (IFD). The actual compressed data is before the
Image File Directory (Tags). In the Image File Directory there
is an offset for the image which is pointing to the beginning
of the file. It looks a little backward, but there is
a reason to it.
TIFF File format originated in the mid 1980s when memory was
very limited. The image was decompressed and compressed
from the video
buffer. An image was segmented and cut up to strips. Each strip
contained 32k or 64k of data and each strip’s offset and
length was written into the IFD. As the image was compressed
one did not know in advance how big the compressed image data
would
be. Therefore one could not fill out the IFD tags until the entire
image strips were written to the file. Once the image is written
to the file then one can write the IFD tags. To make it more
complicated each strip in the image header is an entry, so one
could not compute
how big the IFD would be in advance. Therefore it makes sense
to write the image data first, and then write the IFD tags.
The TIFF specification allows both approaches. The conventional
tiff file structure was dictated by necessity at the time. The
Cisco TIFF approach is more convenient
in an IP application to process the data stream. One can start to decompress
the image before the entire image is received since the header information
is in front of the image.
Cisco TIFF support is
included in the following Black Ice printer drivers:
Home >
Printer
Drivers
>
File Formats > Cisco TIFF Format
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